Preface
Validating data is a common task that occurs throughout all application layers, from the presentation to the persistence layer. Often the same validation logic is implemented in each layer which is time consuming and error-prone. To avoid duplication of these validations, developers often bundle validation logic directly into the domain model, cluttering domain classes with validation code which is really metadata about the class itself.
![application layers](images/application-layers.png)
JSR 349 - Bean Validation 1.1 - defines a metadata model and API for entity and method validation. The default metadata source are annotations, with the ability to override and extend the meta-data through the use of XML. The API is not tied to a specific application tier nor programming model. It is specifically not tied to either web or persistence tier, and is available for both server-side application programming, as well as rich client Swing application developers.
![application layers2](images/application-layers2.png)
Hibernate Validator is the reference implementation of this JSR 349. The implementation itself as well as the Bean Validation API and TCK are all provided and distributed under the Apache Software License 2.0.
1. Getting started
This chapter will show you how to get started with Hibernate Validator, the reference implementation (RI) of Bean Validation. For the following quick-start you need:
-
A JDK >= 6
-
An Internet connection (Maven has to download all required libraries)
1.1. Project set up
In order to use Hibernate Validator within a Maven project, simply add the following dependency to your pom.xml:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.4.3.Final</version>
</dependency>
This transitively pulls in the dependency to the Bean Validation API
(javax.validation:validation-api:1.1.0.Final
).
1.1.1. Unified EL
Hibernate Validator requires an implementation of the Unified Expression Language (JSR 341) for evaluating dynamic expressions in constraint violation messages (see Default message interpolation). When your application runs in a Java EE container such as JBoss AS, an EL implementation is already provided by the container. In a Java SE environment, however, you have to add an implementation as dependency to your POM file. For instance you can add the following two dependencies to use the JSR 341 reference implementation:
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.el</artifactId>
<version>3.0.1-b08</version>
</dependency>
For environments where one cannot provide a EL implementation Hibernate Validator is offering a
|
1.1.2. CDI
Bean Validation defines integration points with CDI (Contexts and Dependency Injection for Java TM EE, JSR 346). If your application runs in an environment which does not provide this integration out of the box, you may use the Hibernate Validator CDI portable extension by adding the following Maven dependency to your POM:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-cdi</artifactId>
<version>5.4.3.Final</version>
</dependency>
Note that adding this dependency is usually not required for applications running on a Java EE application server. You can learn more about the integration of Bean Validation and CDI in CDI.
1.1.3. Running with a security manager
Hibernate Validator supports running with a security manager being enabled. To do so, you must assign several permissions to the Hibernate Validator and the Bean Validation API code bases. The following shows how to do this via a policy file as processed by the Java default policy implementation:
grant codeBase "file:path/to/hibernate-validator-5.4.3.Final.jar" {
permission java.lang.reflect.ReflectPermission "suppressAccessChecks";
permission java.lang.RuntimePermission "accessDeclaredMembers";
permission java.lang.RuntimePermission "setContextClassLoader";
permission org.hibernate.validator.HibernateValidatorPermission "accessPrivateMembers";
// Only needed when working with XML descriptors (validation.xml or XML constraint mappings)
permission java.util.PropertyPermission "mapAnyUriToUri", "read";
};
grant codeBase "file:path/to/validation-api-1.1.0.Final.jar" {
permission java.io.FilePermission "path/to/hibernate-validator-5.4.3.Final.jar", "read";
};
All API invocations requiring special permissions are done via privileged actions. This means only Hibernate Validator and the Bean Validation API themselves need the listed permissions. You don’t need to assign any permissions to other code bases calling Hibernate Validator.
1.1.4. Updating Hibernate Validator in WildFly
The WildFly application server contains Hibernate Validator out of the box. In order to update the server modules for Bean Validation API and Hibernate Validator to the latest and greatest, the patch mechanism of WildFly can be used.
You can download the patch file from SourceForge or from Maven Central using the following dependency:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-modules</artifactId>
<version>5.4.3.Final</version>
<classifier>wildfly-10.1.0.Final-patch</classifier>
<type>zip</type>
</dependency>
Having downloaded the patch file, you can apply it to WildFly by running this command:
$JBOSS_HOME/bin/jboss-cli.sh patch apply hibernate-validator-modules-5.4.3.Final-wildfly-10.1.0.Final-patch.zip
In case you want to undo the patch and go back to the version of Hibernate Validator originally coming with the server, run the following command:
$JBOSS_HOME/bin/jboss-cli.sh patch rollback --reset-configuration=true
1.2. Applying constraints
Lets dive directly into an example to see how to apply constraints.
package org.hibernate.validator.referenceguide.chapter01;
import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
@Min(2)
private int seatCount;
public Car(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}
//getters and setters ...
}
The @NotNull
, @Size
and @Min
annotations are used to declare the constraints which should be applied
to the fields of a Car instance:
-
manufacturer
must never benull
-
licensePlate
must never benull
and must be between 2 and 14 characters long -
seatCount
must be at least 2
You can find the complete source code of all examples used in this reference guide in the Hibernate Validator source repository on GitHub. |
1.3. Validating constraints
To perform a validation of these constraints, you use a Validator
instance. Let’s have a look at a
unit test for Car
:
package org.hibernate.validator.referenceguide.chapter01;
import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import org.junit.BeforeClass;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class CarTest {
private static Validator validator;
@BeforeClass
public static void setUpValidator() {
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
validator = factory.getValidator();
}
@Test
public void manufacturerIsNull() {
Car car = new Car( null, "DD-AB-123", 4 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
}
@Test
public void licensePlateTooShort() {
Car car = new Car( "Morris", "D", 4 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"size must be between 2 and 14",
constraintViolations.iterator().next().getMessage()
);
}
@Test
public void seatCountTooLow() {
Car car = new Car( "Morris", "DD-AB-123", 1 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"must be greater than or equal to 2",
constraintViolations.iterator().next().getMessage()
);
}
@Test
public void carIsValid() {
Car car = new Car( "Morris", "DD-AB-123", 2 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 0, constraintViolations.size() );
}
}
In the setUp()
method a Validator
object is retrieved from the ValidatorFactory
. A Validator
instance is thread-safe and may be reused multiple times. It thus can safely be stored in a static
field and be used in the test methods to validate the different Car
instances.
The validate()
method returns a set of ConstraintViolation
instances, which you can iterate over in
order to see which validation errors occurred. The first three test methods show some expected
constraint violations:
-
The
@NotNull
constraint onmanufacturer
is violated inmanufacturerIsNull()
-
The
@Size
constraint onlicensePlate
is violated inlicensePlateTooShort()
-
The
@Min
constraint onseatCount
is violated inseatCountTooLow()
If the object validates successfully, validate()
returns an empty set as you can see in carIsValid()
.
Note that only classes from the package javax.validation
are used. These are provided from the Bean
Validation API. No classes from Hibernate Validator are directly referenced, resulting in portable
code.
1.4. Java 8 support
Java 8 introduces several enhancements which are valuable from a Hibernate Validator point of view. This section briefly introduces the Hibernate Validator features based on Java 8. They are only available in Hibernate Validator 5.2 and later.
1.4.1. Type arguments constraints
In Java 8 it is possible to use annotations in any location a type is used. This includes type arguments. Hibernate Validator supports the validation of constraints defined on type arguments of collections, maps, and custom parameterized types. The Type argument constraints chapter provides further information on how to apply and use type argument constraints.
1.4.2. Actual parameter names
The Java 8 Reflection API can now retrieve the actual parameter names of a method or constructor.
Hibernate Validator uses this ability to report the actual parameter names instead of arg0
,
arg1
, etc. The ParameterNameProvider
chapter explains how to use the new reflection
based parameter name provider.
1.4.3. New date/time API
Java 8 introduces a new date/time API. Hibernate Validator provides full support for the new API
where @Future
and @Past
constraints can be applied on the new types.
The complete list of types supported for @Future
and @Past
can be found in Bean Validation constraints.
1.4.4. Optional type
Hibernate Validator provides also support for Java 8 Optional
type, by unwrapping the Optional
instance and validating the internal value. Optional unwrapper provides examples and a
further discussion.
1.5. Where to go next?
That concludes the 5 minute tour through the world of Hibernate Validator and Bean Validation. Continue exploring the code examples or look at further examples referenced in Further reading.
To learn more about the validation of beans and properties, just continue reading Declaring and validating bean constraints. If you are interested in using Bean Validation for the validation of method pre- and postcondition refer to Declaring and validating method constraints. In case your application has specific validation requirements have a look at Creating custom constraints.
2. Declaring and validating bean constraints
In this chapter you will learn how to declare (see Declaring bean constraints) and validate (see Validating bean constraints) bean constraints. Built-in constraints provides an overview of all built-in constraints coming with Hibernate Validator.
If you are interested in applying constraints to method parameters and return values, refer to Declaring and validating method constraints.
2.1. Declaring bean constraints
Constraints in Bean Validation are expressed via Java annotations. In this section you will learn how to enhance an object model with these annotations. There are the following three types of bean constraints:
-
field constraints
-
property constraints
-
class constraints
Not all constraints can be placed on all of these levels. In fact, none of the default constraints
defined by Bean Validation can be placed at class level. The |
2.1.1. Field-level constraints
Constraints can be expressed by annotating a field of a class. Field-level constraints shows a field level configuration example:
package org.hibernate.validator.referenceguide.chapter02.fieldlevel;
public class Car {
@NotNull
private String manufacturer;
@AssertTrue
private boolean isRegistered;
public Car(String manufacturer, boolean isRegistered) {
this.manufacturer = manufacturer;
this.isRegistered = isRegistered;
}
//getters and setters...
}
When using field-level constraints field access strategy is used to access the value to be validated. This means the validation engine directly accesses the instance variable and does not invoke the property accessor method even if such an accessor exists.
Constraints can be applied to fields of any access type (public, private etc.). Constraints on static fields are not supported, though.
When validating byte code enhanced objects property level constraints should be used, because the byte code enhancing library won’t be able to determine a field access via reflection. |
2.1.2. Property-level constraints
If your model class adheres to the JavaBeans standard, it is also possible to annotate the properties of a bean class instead of its fields. Property-level constraints uses the same entity as in Field-level constraints, however, property level constraints are used.
package org.hibernate.validator.referenceguide.chapter02.propertylevel;
public class Car {
private String manufacturer;
private boolean isRegistered;
public Car(String manufacturer, boolean isRegistered) {
this.manufacturer = manufacturer;
this.isRegistered = isRegistered;
}
@NotNull
public String getManufacturer() {
return manufacturer;
}
public void setManufacturer(String manufacturer) {
this.manufacturer = manufacturer;
}
@AssertTrue
public boolean isRegistered() {
return isRegistered;
}
public void setRegistered(boolean isRegistered) {
this.isRegistered = isRegistered;
}
}
The property’s getter method has to be annotated, not its setter. That way also read-only properties can be constrained which have no setter method. |
When using property level constraints property access strategy is used to access the value to be validated, i.e. the validation engine accesses the state via the property accessor method.
It is recommended to stick either to field or property annotations within one class. It is not recommended to annotate a field and the accompanying getter method as this would cause the field to be validated twice. |
2.1.3. Type argument constraints
Starting from Java 8, it is possible to specify constraints directly on the type argument of a
parameterized type. However, this requires that ElementType.TYPE_USE
is specified via @Target
in the constraint definition. To maintain backwards compatibility, built-in Bean Validation as well as
Hibernate Validator specific constraints do not yet specify ElementType.TYPE_USE
. To make use of
type argument constraints, custom constraints must be used (see Creating custom constraints).
Hibernate Validator validates type arguments constraints specified on collections, map values,
java.util.Optional
, and custom parameterized types.
With Iterable
When applying constraints on an Iterable
type argument, Hibernate Validator will validate each
element. Type argument constraint on List
shows an example of a
List
with a type argument constraint.
In this example, @ValidPart
is a custom constraint allowed to be used in the TYPE_USE
context.
List
package org.hibernate.validator.referenceguide.chapter02.typeargument.list;
public class Car {
@Valid
private List<@ValidPart String> parts = new ArrayList<>();
public void addPart(String part) {
parts.add( part );
}
//...
}
Car car = new Car();
car.addPart( "Wheel" );
car.addPart( null );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"'null' is not a valid car part.",
constraintViolations.iterator().next().getMessage()
);
assertEquals( "parts[1].<collection element>",
constraintViolations.iterator().next().getPropertyPath().toString() );
With Map
Type argument constraints are also validated for map values. Constraints on the key are ignored.
Type argument constraint on maps shows an example of a Map
value with a type
argument constraint.
package org.hibernate.validator.referenceguide.chapter02.typeargument.map;
public class Car {
public enum FuelConsumption {
CITY,
HIGHWAY
}
@Valid
private EnumMap<FuelConsumption, @MaxAllowedFuelConsumption Integer> fuelConsumption = new EnumMap<>( FuelConsumption.class );
public void setFuelConsumption(FuelConsumption consumption, int value) {
fuelConsumption.put( consumption, value );
}
//...
}
Car car = new Car();
car.setFuelConsumption( Car.FuelConsumption.HIGHWAY, 20 );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "20 is outside the max fuel consumption.", constraintViolations.iterator().next().getMessage() );
With java.util.Optional
When applying a constraint on the type argument of Optional
, Hibernate Validator will automatically
unwrap the type and validate the internal value. Type argument constraint on Optional shows
an example of an Optional
with a type argument constraint.
package org.hibernate.validator.referenceguide.chapter02.typeargument.optional;
public class Car {
private Optional<@MinTowingCapacity(1000) Integer> towingCapacity = Optional.empty();
public void setTowingCapacity(Integer alias) {
towingCapacity = Optional.of( alias );
}
//...
}
Car car = new Car();
car.setTowingCapacity( 100 );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "Not enough towing capacity.",
constraintViolations.iterator().next().getMessage() );
assertEquals( "towingCapacity",
constraintViolations.iterator().next().getPropertyPath().toString() );
With custom parameterized types
Type arguments constraints can with two restrictions also be used with custom types. First, a
ValidatedValueUnwrapper
must be registered for the custom type allowing to retrieve
the value to validate (see Unwrapping values). Second, only types with one type arguments
are supported. Parameterized types with two or more type arguments are not checked for type argument
constraints. This limitation might change in future versions.
Type argument constraint on custom parameterized type shows an example of a custom parameterized type with a type argument constraint.
package org.hibernate.validator.referenceguide.chapter02.typeargument.custom;
public class Car {
private GearBox<@MinTorque(100) Gear> gearBox;
public void setGearBox(GearBox<Gear> gearBox) {
this.gearBox = gearBox;
}
//...
}
package org.hibernate.validator.referenceguide.chapter02.typeargument.custom;
public class GearBox<T extends Gear> {
private final T gear;
public GearBox(T gear) {
this.gear = gear;
}
public Gear getGear() {
return this.gear;
}
}
package org.hibernate.validator.referenceguide.chapter02.typeargument.custom;
public class Gear {
private final Integer torque;
public Gear(Integer torque) {
this.torque = torque;
}
public Integer getTorque() {
return torque;
}
public static class AcmeGear extends Gear {
public AcmeGear() {
super( 100 );
}
}
}
package org.hibernate.validator.referenceguide.chapter02.typeargument.custom;
public class GearBoxUnwrapper extends ValidatedValueUnwrapper<GearBox> {
@Override
public Object handleValidatedValue(GearBox gearBox) {
return gearBox == null ? null : gearBox.getGear();
}
@Override
public Type getValidatedValueType(Type valueType) {
return Gear.class;
}
}
Car car = new Car();
car.setGearBox( new GearBox<>( new Gear.AcmeGear() ) );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "Gear is not providing enough torque.", constraintViolations.iterator().next().getMessage() );
assertEquals( "gearBox", constraintViolations.iterator().next().getPropertyPath().toString() );
2.1.4. Class-level constraints
Last but not least, a constraint can also be placed on the class level. In this case not a single property is subject of the validation but the complete object. Class-level constraints are useful if the validation depends on a correlation between several properties of an object.
The Car class in Class-level constraint has the two attributes seatCount
and passengers
and it
should be ensured that the list of passengers has not more entries than seats are available. For
that purpose the @ValidPassengerCount
constraint is added on the class level. The validator of that
constraint has access to the complete Car
object, allowing to compare the numbers of seats and
passengers.
Refer to Class-level constraints to learn in detail how to implement this custom constraint.
package org.hibernate.validator.referenceguide.chapter02.classlevel;
@ValidPassengerCount
public class Car {
private int seatCount;
private List<Person> passengers;
//...
}
2.1.5. Constraint inheritance
When a class implements an interface or extends another class, all constraint annotations declared on the super-type apply in the same manner as the constraints specified on the class itself. To make things clearer let’s have a look at the following example:
package org.hibernate.validator.referenceguide.chapter02.inheritance;
public class Car {
private String manufacturer;
@NotNull
public String getManufacturer() {
return manufacturer;
}
//...
}
package org.hibernate.validator.referenceguide.chapter02.inheritance;
public class RentalCar extends Car {
private String rentalStation;
@NotNull
public String getRentalStation() {
return rentalStation;
}
//...
}
Here the class RentalCar
is a subclass of Car
and adds the property rentalStation
. If an instance of
RentalCar
is validated, not only the @NotNull
constraint on rentalStation
is evaluated, but also the
constraint on manufacturer
from the parent class.
The same would be true, if Car
was not a superclass but an interface implemented by RentalCar
.
Constraint annotations are aggregated if methods are overridden. So if RentalCar
overrode the
getManufacturer()
method from Car
, any constraints annotated at the overriding method would be
evaluated in addition to the @NotNull
constraint from the superclass.
2.1.6. Object graphs
The Bean Validation API does not only allow to validate single class instances but also complete
object graphs (cascaded validation). To do so, just annotate a field or property representing a
reference to another object with @Valid
as demonstrated in Cascaded validation.
package org.hibernate.validator.referenceguide.chapter02.objectgraph;
public class Car {
@NotNull
@Valid
private Person driver;
//...
}
package org.hibernate.validator.referenceguide.chapter02.objectgraph;
public class Person {
@NotNull
private String name;
//...
}
If an instance of Car
is validated, the referenced Person
object will be validated as well, as the
driver
field is annotated with @Valid
. Therefore the validation of a Car
will fail if the name
field
of the referenced Person
instance is null
.
The validation of object graphs is recursive, i.e. if a reference marked for cascaded validation
points to an object which itself has properties annotated with @Valid
, these references will be
followed up by the validation engine as well. The validation engine will ensure that no infinite
loops occur during cascaded validation, for example if two objects hold references to each other.
Note that null
values are getting ignored during cascaded validation.
Object graph validation also works for collection-typed fields. That means any attributes that
-
are arrays
-
implement
java.lang.Iterable
(especiallyCollection
,List
andSet
) -
implement
java.util.Map
can be annotated with @Valid
, which will cause each contained element to be validated, when the
parent object is validated.
package org.hibernate.validator.referenceguide.chapter02.objectgraph.list;
public class Car {
@NotNull
@Valid
private List<Person> passengers = new ArrayList<Person>();
//...
}
So when validating an instance of the Car
class shown in Cascaded validation of a collection, a
ConstraintViolation
will be created, if any of the Person
objects contained in the passengers list
has a null
name.
2.2. Validating bean constraints
The Validator
interface is the most important object in Bean Validation. The next section shows how
to obtain an Validator
instance. Afterwards you’ll learn how to use the different methods of the
Validator
interface.
2.2.1. Obtaining a Validator
instance
The first step towards validating an entity instance is to get hold of a Validator
instance. The
road to this instance leads via the Validation
class and a ValidatorFactory
. The easiest way is to
use the static method Validation#buildDefaultValidatorFactory()
:
Validation#buildDefaultValidatorFactory()
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
validator = factory.getValidator();
This bootstraps a validator in the default configuration. Refer to Bootstrapping to
learn more about the different bootstrapping methods and how to obtain a specifically configured
Validator
instance.
2.2.2. Validator methods
The Validator
interface contains three methods that can be used to either validate entire entities
or just single properties of the entity.
All three methods return a Set<ConstraintViolation>
. The set is empty, if the validation succeeds.
Otherwise a ConstraintViolation
instance is added for each violated constraint.
All the validation methods have a var-args parameter which can be used to specify, which validation
groups shall be considered when performing the validation. If the parameter is not specified the
default validation group (javax.validation.groups.Default
) is used. The topic of validation groups
is discussed in detail in Grouping constraints.
Validator#validate()
Use the validate()
method to perform validation of all constraints of a given bean.
Using Validator#validate()
shows the validation of an instance of the Car
class from
Property-level constraints which fails to satisfy the @NotNull
constraint on the manufacturer
property. The validation call therefore returns one ConstraintViolation
object.
Validator#validate()
Car car = new Car( null, true );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
Validator#validateProperty()
With help of the validateProperty()
you can validate a single named property of a given object. The
property name is the JavaBeans property name.
Validator#validateProperty()
Car car = new Car( null, true );
Set<ConstraintViolation<Car>> constraintViolations = validator.validateProperty(
car,
"manufacturer"
);
assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
Validator#validateValue()
By using the validateValue()
method you can check whether a single property of a given class can be
validated successfully, if the property had the specified value:
Validator#validateValue()
Set<ConstraintViolation<Car>> constraintViolations = validator.validateValue(
Car.class,
"manufacturer",
null
);
assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
|
Validator#validateProperty()
is for example used in the integration of Bean Validation into JSF 2
(see JSF & Seam) to perform a validation of the values entered into a form
before they are propagated to the model.
2.2.3. ConstraintViolation
methods
Now it is time to have a closer look at what a ConstraintViolation
is.
Using the different methods of ConstraintViolation
a lot of useful information about the cause of the validation failure can be determined.
The following gives an overview of these methods.
The values under "Example" column refer to Using Validator#validate()
.
getMessage()
-
The interpolated error message
- Example
-
"may not be null"
getMessageTemplate()
-
The non-interpolated error message
- Example
-
"{… NotNull.message}"
getRootBean()
-
The root bean being validated
- Example
-
car
getRootBeanClass()
-
The class of the root bean being validated
- Example
-
Car.class
getLeafBean()
-
If a bean constraint, the bean instance the constraint is applied on; if a property constraint, the bean instance hosting the property the constraint is applied on
- Example
-
car
getPropertyPath()
-
The property path to the validated value from root bean
- Example
-
contains one node with kind
PROPERTY
and name "manufacturer"
getInvalidValue()
-
The value failing to pass the constraint
- Example
-
null
getConstraintDescriptor()
-
Constraint metadata reported to fail
- Example
-
descriptor for
@NotNull
2.3. Built-in constraints
Hibernate Validator comprises a basic set of commonly used constraints. These are foremost the constraints defined by the Bean Validation specification (see Bean Validation constraints). Additionally, Hibernate Validator provides useful custom constraints (see Additional constraints).
2.3.1. Bean Validation constraints
Below you can find a list of all constraints specified in the Bean Validation API. All these constraints apply to the field/property level, there are no class-level constraints defined in the Bean Validation specification. If you are using the Hibernate object-relational mapper, some of the constraints are taken into account when creating the DDL for your model (see "Hibernate metadata impact").
Hibernate Validator allows some constraints to be applied to more data types than required by the
Bean Validation specification (e.g. |
@AssertFalse
-
Checks that the annotated element is false
- Supported data types
-
Boolean
,boolean
- Hibernate metadata impact
-
None
@AssertTrue
-
Checks that the annotated element is true
- Supported data types
-
Boolean
,boolean
- Hibernate metadata impact
-
None
@DecimalMax(value=, inclusive=)
-
Checks whether the annotated value is less than the specified maximum, when
inclusive
=false. Otherwise whether the value is less than or equal to the specified maximum. The parameter value is the string representation of the max value according to theBigDecimal
string representation.- Supported data types
-
BigDecimal
,BigInteger
,CharSequence
,byte
,short
,int
,long
and the respective wrappers of the primitive types; additionally supported by HV: any sub-type ofNumber
andjavax.money.MonetaryAmount
(if the JSR 354 API and an implementation is on the class path) - Hibernate metadata impact
-
None
@DecimalMin(value=, inclusive=)
-
Checks whether the annotated value is larger than the specified minimum, when
inclusive
=false. Otherwise whether the value is larger than or equal to the specified minimum. The parameter value is the string representation of the min value according to theBigDecimal
string representation.- Supported data types
-
BigDecimal
,BigInteger
,CharSequence
,byte
,short
,int
,long
and the respective wrappers of the primitive types; additionally supported by HV: any sub-type ofNumber
andjavax.money.MonetaryAmount
- Hibernate metadata impact
-
None
@Digits(integer=, fraction=)
-
Checks whether the annotated value is a number having up to
integer
digits andfraction
fractional digits- Supported data types
-
BigDecimal,
BigInteger
,CharSequence
,byte
,short
,int
,long
and the respective wrappers of the primitive types; additionally supported by HV: any sub-type ofNumber
- Hibernate metadata impact
-
Defines column precision and scale
@Future
-
Checks whether the annotated date is in the future
- Supported data types
-
java.util.Date
,java.util.Calendar
,java.time.chrono.ChronoZonedDateTime
,java.time.Instant
,java.time.OffsetDateTime
; additionally supported by HV, if the Joda Time date/time API is on the classpath: any implementations ofReadablePartial
andReadableInstant
- Hibernate metadata impact
-
None
@Max(value=)
-
Checks whether the annotated value is less than or equal to the specified maximum
- Supported data types
-
BigDecimal
,BigInteger
,byte
,short
,int
,long
and the respective wrappers of the primitive types; additionally supported by HV: any sub-type ofCharSequence
(the numeric value represented by the character sequence is evaluated), any sub-type ofNumber
andjavax.money.MonetaryAmount
- Hibernate metadata impact
-
Adds a check constraint on the column
@Min(value=)
-
Checks whether the annotated value is higher than or equal to the specified minimum
- Supported data types
-
BigDecimal
,BigInteger
,byte
,short
,int
,long
and the respective wrappers of the primitive types; additionally supported by HV: any sub-type ofCharSequence
(the numeric value represented by the character sequence is evaluated), any sub-type ofNumber
andjavax.money.MonetaryAmount
- Hibernate metadata impact
-
Adds a check constraint on the column
@NotNull
-
Checks that the annotated value is not
null
- Supported data types
-
Any type
- Hibernate metadata impact
-
Column(s) are not nullable
@Null
-
Checks that the annotated value is
null
- Supported data types
-
Any type
- Hibernate metadata impact
-
None
@Past
-
Checks whether the annotated date is in the past
- Supported data types
-
java.util.Date
,java.util.Calendar
,java.time.chrono.ChronoZonedDateTime
,java.time.Instant
,java.time.OffsetDateTime
; Additionally supported by HV, if the Joda Time date/time API is on the classpath: any implementations ofReadablePartial
andReadableInstant
- Hibernate metadata impact
-
None
@Pattern(regex=, flags=)
-
Checks if the annotated string matches the regular expression
regex
considering the given flagmatch
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Size(min=, max=)
-
Checks if the annotated element’s size is between
min
andmax
(inclusive)- Supported data types
-
CharSequence
,Collection
,Map
and arrays - Hibernate metadata impact
-
Column length will be set to
max
@Valid
-
Performs validation recursively on the associated object. If the object is a collection or an array, the elements are validated recursively. If the object is a map, the value elements are validated recursively.
- Supported data types
-
Any non-primitive type
- Hibernate metadata impact
-
None
On top of the parameters listed above each constraint has the parameters message, groups and payload. This is a requirement of the Bean Validation specification. |
2.3.2. Additional constraints
In addition to the constraints defined by the Bean Validation API Hibernate Validator provides several useful custom constraints which are listed below.
With one exception also these constraints apply to the field/property level, only @ScriptAssert
is a class-level constraint.
@CreditCardNumber(ignoreNonDigitCharacters=)
-
Checks that the annotated character sequence passes the Luhn checksum test. Note, this validation aims to check for user mistakes, not credit card validity! See also Anatomy of Credit Card Numbers.
ignoreNonDigitCharacters
allows to ignore non digit characters. The default isfalse
.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Currency(value=)
-
Checks that the currency unit of the annotated
javax.money.MonetaryAmount
is part of the specified currency units.- Supported data types
-
any sub-type of
javax.money.MonetaryAmount
(if the JSR 354 API and an implementation is on the class path) - Hibernate metadata impact
-
None
@EAN
-
Checks that the annotated character sequence is a valid EAN barcode. type determines the type of barcode. The default is EAN-13.
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Email
-
Checks whether the specified character sequence is a valid email address. The optional parameters
regexp
andflags
allow to specify an additional regular expression (including regular expression flags) which the email must match.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Length(min=, max=)
-
Validates that the annotated character sequence is between
min
andmax
included- Supported data types
-
CharSequence
- Hibernate metadata impact
-
Column length will be set to max
@LuhnCheck(startIndex= , endIndex=, checkDigitIndex=, ignoreNonDigitCharacters=)
-
Checks that the digits within the annotated character sequence pass the Luhn checksum algorithm (see also Luhn algorithm).
startIndex
andendIndex
allow to only run the algorithm on the specified sub-string.checkDigitIndex
allows to use an arbitrary digit within the character sequence as the check digit. If not specified it is assumed that the check digit is part of the specified range. Last but not least,ignoreNonDigitCharacters
allows to ignore non digit characters.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Mod10Check(multiplier=, weight=, startIndex=, endIndex=, checkDigitIndex=, ignoreNonDigitCharacters=)
-
Checks that the digits within the annotated character sequence pass the generic mod 10 checksum algorithm.
multiplier
determines the multiplier for odd numbers (defaults to 3),weight
the weight for even numbers (defaults to 1).startIndex
andendIndex
allow to only run the algorithm on the specified sub-string.checkDigitIndex
allows to use an arbitrary digit within the character sequence as the check digit. If not specified it is assumed that the check digit is part of the specified range. Last but not least,ignoreNonDigitCharacters
allows to ignore non digit characters.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@Mod11Check(threshold=, startIndex=, endIndex=, checkDigitIndex=, ignoreNonDigitCharacters=, treatCheck10As=, treatCheck11As=)
-
Checks that the digits within the annotated character sequence pass the mod 11 checksum algorithm.
threshold
specifies the threshold for the mod11 multiplier growth; if no value is specified the multiplier will grow indefinitely.treatCheck10As
andtreatCheck11As
specify the check digits to be used when the mod 11 checksum equals 10 or 11, respectively. Default to X and 0, respectively.startIndex
,endIndex
checkDigitIndex
andignoreNonDigitCharacters
carry the same semantics as in@Mod10Check
.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@NotBlank
-
Checks that the annotated character sequence is not null and the trimmed length is greater than 0. The difference to
@NotEmpty
is that this constraint can only be applied on strings and that trailing white-spaces are ignored.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@NotEmpty
-
Checks whether the annotated element is not null nor empty
- Supported data types
-
CharSequence
,Collection
,Map
and arrays - Hibernate metadata impact
-
None
@Range(min=, max=)
-
Checks whether the annotated value lies between (inclusive) the specified minimum and maximum
- Supported data types
-
BigDecimal
,BigInteger
,CharSequence
,byte
,short
,int
,long
and the respective wrappers of the primitive types - Hibernate metadata impact
-
None
@SafeHtml(whitelistType= , additionalTags=, additionalTagsWithAttributes=)
-
Checks whether the annotated value contains potentially malicious fragments such as
<script/>
. In order to use this constraint, the jsoup library must be part of the class path. With thewhitelistType
attribute a predefined whitelist type can be chosen which can be refined viaadditionalTags
oradditionalTagsWithAttributes
. The former allows to add tags without any attributes, whereas the latter allows to specify tags and optionally allowed attributes using the annotation@SafeHtml.Tag
.- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
@ScriptAssert(lang=, script=, alias=, reportOn=)
-
Checks whether the given script can successfully be evaluated against the annotated element. In order to use this constraint, an implementation of the Java Scripting API as defined by JSR 223 ("Scripting for the JavaTM Platform") must be a part of the class path. The expressions to be evaluated can be written in any scripting or expression language, for which a JSR 223 compatible engine can be found in the class path. Even though this is a class-level constraint, one can use the
reportOn
attribute to report a constraint violation on a specific property rather than the whole object.- Supported data types
-
Any type
- Hibernate metadata impact
-
None
@URL(protocol=, host=, port=, regexp=, flags=)
-
Checks if the annotated character sequence is a valid URL according to RFC2396. If any of the optional parameters
protocol
,host
orport
are specified, the corresponding URL fragments must match the specified values. The optional parametersregexp
andflags
allow to specify an additional regular expression (including regular expression flags) which the URL must match. Per default this constraint used thejava.net.URL
constructor to verify whether a given string represents a valid URL. A regular expression based version is also available -RegexpURLValidator
- which can be configured via XML (see Mapping constraints viaconstraint-mappings
) or the programmatic API (see Adding constraint definitions programmatically).- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
Country specific constraints
Hibernate Validator offers also some country specific constraints, e.g. for the validation of social security numbers.
If you have to implement a country specific constraint, consider making it a contribution to Hibernate Validator! |
@CNPJ
-
Checks that the annotated character sequence represents a Brazilian corporate tax payer registry number (Cadastro de Pessoa JurÃeddica)
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Brazil
@CPF
-
Checks that the annotated character sequence represents a Brazilian individual taxpayer registry number (Cadastro de Pessoa FÃdsica)
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Brazil
@TituloEleitoral
-
Checks that the annotated character sequence represents a Brazilian voter ID card number (TÃtulo Eleitoral)
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Brazil
@NIP
-
Checks that the annotated character sequence represents a Polish VAT identification number (NIP)
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Poland
@PESEL
-
Checks that the annotated character sequence represents a Polish national identification number (PESEL)
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Poland
@REGON
-
Checks that the annotated character sequence represents a Polish taxpayer identification number (REGON). Can be applied to both 9 and 14 digits versions of REGON
- Supported data types
-
CharSequence
- Hibernate metadata impact
-
None
- Country
-
Poland
In some cases neither the Bean Validation constraints nor the custom constraints provided by Hibernate Validator will fulfill your requirements. In this case you can easily write your own constraint. You can find more information in Creating custom constraints. |
3. Declaring and validating method constraints
As of Bean Validation 1.1, constraints can not only be applied to JavaBeans and their properties, but also to the parameters and return values of the methods and constructors of any Java type. That way Bean Validation constraints can be used to specify
-
the preconditions that must be satisfied by the caller before a method or constructor may be invoked (by applying constraints to the parameters of an executable)
-
the postconditions that are guaranteed to the caller after a method or constructor invocation returns (by applying constraints to the return value of an executable)
For the purpose of this reference guide, the term method constraint refers to both, method and constructor constraints, if not stated otherwise. Occasionally, the term executable is used when referring to methods and constructors. |
This approach has several advantages over traditional ways of checking the correctness of parameters and return values:
-
the checks don’t have to be performed manually (e.g. by throwing
IllegalArgumentException
or similar), resulting in less code to write and maintain -
an executable’s pre- and postconditions don’t have to be expressed again in its documentation, since the constraint annotations will automatically be included in the generated JavaDoc. This avoids redundancies and reduces the chance of inconsistencies between implementation and documentation
In order to make annotations show up in the JavaDoc of annotated elements, the annotation types themselves must be annotated with the meta annotation @Documented. This is the case for all built-in constraints and is considered a best practice for any custom constraints. |
In the remainder of this chapter you will learn how to declare parameter and return value
constraints and how to validate them using the ExecutableValidator
API.
3.1. Declaring method constraints
3.1.1. Parameter constraints
You specify the preconditions of a method or constructor by adding constraint annotations to its parameters as demonstrated in Declaring method and constructor parameter constraints.
package org.hibernate.validator.referenceguide.chapter03.parameter;
public class RentalStation {
public RentalStation(@NotNull String name) {
//...
}
public void rentCar(
@NotNull Customer customer,
@NotNull @Future Date startDate,
@Min(1) int durationInDays) {
//...
}
}
The following preconditions are declared here:
-
The
name
passed to theRentalCar
constructor must not benull
-
When invoking the
rentCar()
method, the givencustomer
must not benull
, the rental’s start date must not benull
as well as be in the future and finally the rental duration must be at least one day
Note that declaring method or constructor constraints itself does not automatically cause their
validation upon invocation of the executable. Instead, the ExecutableValidator
API (see
Validating method constraints) must be used to perform the validation, which is
often done using a method interception facility such as AOP, proxy objects etc.
Constraints may only be applied to instance methods, i.e. declaring constraints on static methods is not supported. Depending on the interception facility you use for triggering method validation, additional restrictions may apply, e.g. with respect to the visibility of methods supported as target of interception. Refer to the documentation of the interception technology to find out whether any such limitations exist.
Cross-parameter constraints
Sometimes validation does not only depend on a single parameter but on several or even all parameters of a method or constructor. This kind of requirement can be fulfilled with help of a cross-parameter constraint.
Cross-parameter constraints can be considered as the method validation equivalent to class-level constraints. Both can be used to implement validation requirements which are based on several elements. While class-level constraints apply to several properties of a bean, cross-parameter constraints apply to several parameters of an executable.
In contrast to single-parameter constraints, cross-parameter constraints are declared on the method
or constructor as you can see in Declaring a cross-parameter constraint. Here the cross-
parameter constraint @LuggageCountMatchesPassengerCount
declared on the load()
method is used to
ensure that no passenger has more than two pieces of luggage.
package org.hibernate.validator.referenceguide.chapter03.crossparameter;
public class Car {
@LuggageCountMatchesPassengerCount(piecesOfLuggagePerPassenger = 2)
public void load(List<Person> passengers, List<PieceOfLuggage> luggage) {
//...
}
}
As you will learn in the next section, return value constraints are also declared on the method
level. In order to distinguish cross-parameter constraints from return value constraints, the
constraint target is configured in the ConstraintValidator
implementation using the
@SupportedValidationTarget
annotation. You can find out about the details in
Cross-parameter constraints which shows how to implement your own cross-parameter constraint.
In some cases a constraint can be applied to an executable’s parameters (i.e. it is a cross- parameter constraint), but also to the return value. One example for this are custom constraints which allow to specify validation rules using expression or script languages.
Such constraints must define a member validationAppliesTo()
which can be used at declaration time to
specify the constraint target. As shown in Specifying a constraint’s target you apply the
constraint to an executable’s parameters by specifying
validationAppliesTo = ConstraintTarget.PARAMETERS
, while ConstraintTarget.RETURN_VALUE
is used
to apply the constraint to the executable return value.
package org.hibernate.validator.referenceguide.chapter03.crossparameter.constrainttarget;
public class Garage {
@ELAssert(expression = "...", validationAppliesTo = ConstraintTarget.PARAMETERS)
public Car buildCar(List<Part> parts) {
//...
return null;
}
@ELAssert(expression = "...", validationAppliesTo = ConstraintTarget.RETURN_VALUE)
public Car paintCar(int color) {
//...
return null;
}
}
Although such a constraint is applicable to the parameters and return value of an executable, the target can often be inferred automatically. This is the case, if the constraint is declared on
-
a void method with parameters (the constraint applies to the parameters)
-
an executable with return value but no parameters (the constraint applies to the return value)
-
neither a method nor a constructor, but a field, parameter etc. (the constraint applies to the annotated element)
In these situations you don’t have to specify the constraint target. It is still recommended to do so if it increases readability of the source code. If the constraint target is not specified in situations where it can’t be determined automatically, a ConstraintDeclarationException is raised.
3.1.2. Return value constraints
The postconditions of a method or constructor are declared by adding constraint annotations to the executable as shown in Declaring method and constructor return value constraints.
package org.hibernate.validator.referenceguide.chapter03.returnvalue;
public class RentalStation {
@ValidRentalStation
public RentalStation() {
//...
}
@NotNull
@Size(min = 1)
public List<Customer> getCustomers() {
//...
return null;
}
}
The following constraints apply to the executables of RentalStation:
-
Any newly created
RentalStation
object must satisfy the@ValidRentalStation
constraint -
The customer list returned by
getCustomers()
must not benull
and must contain at least on element
3.1.3. Cascaded validation
Similar to the cascaded validation of JavaBeans properties (see
Object graphs), the @Valid
annotation can be used to mark executable
parameters and return values for cascaded validation. When validating a parameter or return value
annotated with @Valid
, the constraints declared on the parameter or return value object are
validated as well.
In Marking executable parameters and return values for cascaded validation, the car
parameter of the method Garage#checkCar()
as
well as the return value of the Garage
constructor are marked for cascaded validation.
package org.hibernate.validator.referenceguide.chapter03.cascaded;
public class Garage {
@NotNull
private String name;
@Valid
public Garage(String name) {
this.name = name;
}
public boolean checkCar(@Valid @NotNull Car car) {
//...
return false;
}
}
package org.hibernate.validator.referenceguide.chapter03.cascaded;
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
public Car(String manufacturer, String licencePlate) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
}
//getters and setters ...
}
When validating the arguments of the checkCar()
method, the constraints on the properties of the
passed Car
object are evaluated as well. Similarly, the @NotNull
constraint on the name field of
Garage
is checked when validating the return value of the Garage
constructor.
Generally, the cascaded validation works for executables in exactly the same way as it does for JavaBeans properties.
In particular, null
values are ignored during cascaded validation (naturally this can’t happen
during constructor return value validation) and cascaded validation is performed recursively, i.e.
if a parameter or return value object which is marked for cascaded validation itself has properties
marked with @Valid
, the constraints declared on the referenced elements will be validated as well.
Cascaded validation can not only be applied to simple object references but also to collection-typed
parameters and return values. This means when putting the @Valid
annotation to a parameter or return
value which
-
is an array
-
implements
java.lang.Iterable
-
or implements
java.util.Map
each contained element gets validated. So when validating the arguments of the checkCars()
method in
List-typed method parameter marked for cascaded validation, each element instance of the passed list will
be validated and a ConstraintViolation
created when any of the contained Car
instances is invalid.
package org.hibernate.validator.referenceguide.chapter03.cascaded.collection;
public class Garage {
public boolean checkCars(@Valid @NotNull List<Car> cars) {
//...
return false;
}
}
3.1.4. Method constraints in inheritance hierarchies
When declaring method constraints in inheritance hierarchies, it is important to be aware of the following rules:
-
The preconditions to be satisfied by the caller of a method may not be strengthened in subtypes
-
The postconditions guaranteed to the caller of a method may not be weakened in subtypes
These rules are motivated by the concept of behavioral subtyping which requires that wherever a
type T
is used, also a subtype S
of T
may be used without altering the program’s behavior.
As an example, consider a class invoking a method on an object with the static type T
. If the
runtime type of that object was S
and S
imposed additional preconditions, the client class might
fail to satisfy these preconditions as is not aware of them. The rules of behavioral subtyping are
also known as the Liskov
substitution principle.
The Bean Validation specification implements the first rule by disallowing parameter constraints on methods which override or implement a method declared in a supertype (superclass or interface). Illegal method parameter constraint in subtype shows a violation of this rule.
package org.hibernate.validator.referenceguide.chapter03.inheritance.parameter;
public interface Vehicle {
void drive(@Max(75) int speedInMph);
}
package org.hibernate.validator.referenceguide.chapter03.inheritance.parameter;
public class Car implements Vehicle {
@Override
public void drive(@Max(55) int speedInMph) {
//...
}
}
The @Max
constraint on Car#drive()
is illegal since this method implements the interface method
Vehicle#drive()
. Note that parameter constraints on overriding methods are also disallowed, if the
supertype method itself doesn’t declare any parameter constraints.
Furthermore, if a method overrides or implements a method declared in several parallel supertypes
(e.g. two interfaces not extending each other or a class and an interface not implemented by that
class), no parameter constraints may be specified for the method in any of the involved types. The
types in Illegal method parameter constraint in parallel types of a hierarchy demonstrate a violation of that
rule. The method RacingCar#drive()
overrides Vehicle#drive()
as well as Car#drive()
.
Therefore the constraint on Vehicle#drive()
is illegal.
package org.hibernate.validator.referenceguide.chapter03.inheritance.parallel;
public interface Vehicle {
void drive(@Max(75) int speedInMph);
}
package org.hibernate.validator.referenceguide.chapter03.inheritance.parallel;
public interface Car {
void drive(int speedInMph);
}
package org.hibernate.validator.referenceguide.chapter03.inheritance.parallel;
public class RacingCar implements Car, Vehicle {
@Override
public void drive(int speedInMph) {
//...
}
}
The previously described restrictions only apply to parameter constraints. In contrast, return value constraints may be added in methods overriding or implementing any supertype methods.
In this case, all the method’s return value constraints apply for the subtype method, i.e. the constraints declared on the subtype method itself as well as any return value constraints on overridden/implemented supertype methods. This is legal as putting additional return value constraints in place may never represent a weakening of the postconditions guaranteed to the caller of a method.
So when validating the return value of the method Car#getPassengers()
shown in
Return value constraints on supertype and subtype method, the @Size
constraint on the method itself as well
as the @NotNull
constraint on the implemented interface method Vehicle#getPassengers()
apply.
package org.hibernate.validator.referenceguide.chapter03.inheritance.returnvalue;
public interface Vehicle {
@NotNull
List<Person> getPassengers();
}
package org.hibernate.validator.referenceguide.chapter03.inheritance.returnvalue;
public class Car implements Vehicle {
@Override
@Size(min = 1)
public List<Person> getPassengers() {
//...
return null;
}
}
If the validation engine detects a violation of any of the aforementioned rules, a
ConstraintDeclarationException
will be raised.
The rules described in this section only apply to methods but not constructors. By definition, constructors never override supertype constructors. Therefore, when validating the parameters or the return value of a constructor invocation only the constraints declared on the constructor itself apply, but never any constraints declared on supertype constructors. |
Enforcement of these rules may be relaxed by setting the configuration parameters contained in
the |
3.2. Validating method constraints
The validation of method constraints is done using the ExecutableValidator
interface.
In Obtaining an ExecutableValidator
instance you will learn how to obtain an ExecutableValidator
instance while ExecutableValidator
methods shows how to use the different methods
offered by this interface.
Instead of calling the ExecutableValidator
methods directly from within application code, they are
usually invoked via a method interception technology such as AOP, proxy objects, etc. This causes
executable constraints to be validated automatically and transparently upon method or constructor
invocation. Typically a ConstraintViolationException
is raised by the integration layer in case any
of the constraints is violated.
3.2.1. Obtaining an ExecutableValidator
instance
You can retrieve an ExecutableValidator
instance via Validator#forExecutables()
as shown in
Obtaining an ExecutableValidator
instance.
ExecutableValidator
instanceValidatorFactory factory = Validation.buildDefaultValidatorFactory();
executableValidator = factory.getValidator().forExecutables();
In the example the executable validator is retrieved from the default validator factory, but if
required you could also bootstrap a specifically configured factory as described in
Bootstrapping, for instance in order to use a specific parameter name provider
(see ParameterNameProvider
).
3.2.2. ExecutableValidator
methods
The ExecutableValidator
interface offers altogether four methods:
-
validateParameters()
andvalidateReturnValue()
for method validation -
validateConstructorParameters()
andvalidateConstructorReturnValue()
for constructor validation
Just as the methods on Validator
, all these methods return a Set<ConstraintViolation>
which contains
a ConstraintViolation
instance for each violated constraint and which is empty if the validation
succeeds. Also all the methods have a var-args groups parameter by which you can pass the validation
groups to be considered for validation.
The examples in the following sections are based on the methods on constructors of the Car
class
shown in Class Car
with constrained methods and constructors.
Car
with constrained methods and constructorspackage org.hibernate.validator.referenceguide.chapter03.validation;
public class Car {
public Car(@NotNull String manufacturer) {
//...
}
@ValidRacingCar
public Car(String manufacturer, String team) {
//...
}
public void drive(@Max(75) int speedInMph) {
//...
}
@Size(min = 1)
public List<Passenger> getPassengers() {
//...
return Collections.emptyList();
}
}
ExecutableValidator#validateParameters()
The method validateParameters()
is used to validate the arguments of a method invocation.
Using ExecutableValidator#validateParameters()
shows an example. The validation results in a
violation of the @Max
constraint on the parameter of the drive()
method.
ExecutableValidator#validateParameters()
Car object = new Car( "Morris" );
Method method = Car.class.getMethod( "drive", int.class );
Object[] parameterValues = { 80 };
Set<ConstraintViolation<Car>> violations = executableValidator.validateParameters(
object,
method,
parameterValues
);
assertEquals( 1, violations.size() );
Class<? extends Annotation> constraintType = violations.iterator()
.next()
.getConstraintDescriptor()
.getAnnotation()
.annotationType();
assertEquals( Max.class, constraintType );
Note that validateParameters()
validates all the parameter constraints of a method, i.e. constraints
on individual parameters as well as cross-parameter constraints.
ExecutableValidator#validateReturnValue()
Using validateReturnValue()
the return value of a method can can be validated. The validation in
Using ExecutableValidator#validateReturnValue()
yields one constraint violation since the
getPassengers()
method is expect to return at least one Passenger
instance.
ExecutableValidator#validateReturnValue()
Car object = new Car( "Morris" );
Method method = Car.class.getMethod( "getPassengers" );
Object returnValue = Collections.<Passenger>emptyList();
Set<ConstraintViolation<Car>> violations = executableValidator.validateReturnValue(
object,
method,
returnValue
);
assertEquals( 1, violations.size() );
Class<? extends Annotation> constraintType = violations.iterator()
.next()
.getConstraintDescriptor()
.getAnnotation()
.annotationType();
assertEquals( Size.class, constraintType );
ExecutableValidator#validateConstructorParameters()
The arguments of constructor invocations can be validated with validateConstructorParameters()
as
shown in method Using ExecutableValidator#validateConstructorParameters()
. Due to the
@NotNull
constraint on the manufacturer parameter, the validation call returns one constraint
violation.
ExecutableValidator#validateConstructorParameters()
Constructor<Car> constructor = Car.class.getConstructor( String.class );
Object[] parameterValues = { null };
Set<ConstraintViolation<Car>> violations = executableValidator.validateConstructorParameters(
constructor,
parameterValues
);
assertEquals( 1, violations.size() );
Class<? extends Annotation> constraintType = violations.iterator()
.next()
.getConstraintDescriptor()
.getAnnotation()
.annotationType();
assertEquals( NotNull.class, constraintType );
ExecutableValidator#validateConstructorReturnValue()
Finally, by using validateConstructorReturnValue()
you can validate a constructor’s return value. In
Using ExecutableValidator#validateConstructorReturnValue()
, validateConstructorReturnValue()
returns one constraint violation, since the Car
instance returned by the constructor doesn’t satisfy
the @ValidRacingCar
constraint (not shown).
ExecutableValidator#validateConstructorReturnValue()
//constructor for creating racing cars
Constructor<Car> constructor = Car.class.getConstructor( String.class, String.class );
Car createdObject = new Car( "Morris", null );
Set<ConstraintViolation<Car>> violations = executableValidator.validateConstructorReturnValue(
constructor,
createdObject
);
assertEquals( 1, violations.size() );
Class<? extends Annotation> constraintType = violations.iterator()
.next()
.getConstraintDescriptor()
.getAnnotation()
.annotationType();
assertEquals( ValidRacingCar.class, constraintType );
3.2.3. ConstraintViolation
methods for method validation
In addition to the methods introduced in ConstraintViolation
methods,
ConstraintViolation
provides two more methods specific to the validation of executable parameters
and return values.
ConstraintViolation#getExecutableParameters()
returns the validated parameter array in case of
method or constructor parameter validation, while ConstraintViolation#getExecutableReturnValue()
provides access to the validated object in case of return value validation.
All the other ConstraintViolation
methods generally work for method validation in the same way as
for validation of beans. Refer to the JavaDoc to learn more about the
behavior of the individual methods and their return values during bean and method validation.
Note that getPropertyPath()
can be very useful in order to obtain detailed information about the
validated parameter or return value, e.g. for logging purposes. In particular, you can retrieve name
and argument types of the concerned method as well as the index of the concerned parameter from the
path nodes. How this can be done is shown in Retrieving method and parameter information.
Car object = new Car( "Morris" );
Method method = Car.class.getMethod( "drive", int.class );
Object[] parameterValues = { 80 };
Set<ConstraintViolation<Car>> violations = executableValidator.validateParameters(
object,
method,
parameterValues
);
assertEquals( 1, violations.size() );
Iterator<Node> propertyPath = violations.iterator()
.next()
.getPropertyPath()
.iterator();
MethodNode methodNode = propertyPath.next().as( MethodNode.class );
assertEquals( "drive", methodNode.getName() );
assertEquals( Arrays.<Class<?>>asList( int.class ), methodNode.getParameterTypes() );
ParameterNode parameterNode = propertyPath.next().as( ParameterNode.class );
assertEquals( "arg0", parameterNode.getName() );
assertEquals( 0, parameterNode.getParameterIndex() );
The parameter name is determined using the current ParameterNameProvider
(see
ParameterNameProvider
) and defaults to arg0
, arg1
etc.
3.3. Built-in method constraints
In addition to the built-in bean and property-level constraints discussed in
Built-in constraints, Hibernate Validator currently provides one method-level constraint,
@ParameterScriptAssert
. This is a generic cross-parameter constraint which allows to implement
validation routines using any JSR 223 compatible ("Scripting for the JavaTM Platform") scripting
language, provided an engine for this language is available on the classpath.
To refer to the executable’s parameters from within the expression, use their name as obtained from
the active parameter name provider (see ParameterNameProvider
).
Using @ParameterScriptAssert
shows how the validation logic of the @LuggageCountMatchesPassengerCount
constraint from Declaring a cross-parameter constraint could be expressed with the help of
@ParameterScriptAssert
.
@ParameterScriptAssert
package org.hibernate.validator.referenceguide.chapter03.parameterscriptassert;
public class Car {
@ParameterScriptAssert(lang = "javascript", script = "arg1.size() <= arg0.size() * 2")
public void load(List<Person> passengers, List<PieceOfLuggage> luggage) {
//...
}
}
4. Interpolating constraint error messages
Message interpolation is the process of creating error messages for violated Bean Validation constraints. In this chapter you will learn how such messages are defined and resolved and how you can plug in custom message interpolators in case the default algorithm is not sufficient for your requirements.
4.1. Default message interpolation
Constraint violation messages are retrieved from so called message descriptors. Each constraint defines its default message descriptor using the message attribute. At declaration time, the default descriptor can be overridden with a specific value as shown in Specifying a message descriptor using the message attribute.
package org.hibernate.validator.referenceguide.chapter04;
public class Car {
@NotNull(message = "The manufacturer name must not be null")
private String manufacturer;
//constructor, getters and setters ...
}
If a constraint is violated, its descriptor will be interpolated by the validation engine using the
currently configured MessageInterpolator
. The interpolated error message can then be retrieved from
the resulting constraint violation by calling ConstraintViolation#getMessage()
.
Message descriptors can contain message parameters as well as message expressions which will be
resolved during interpolation. Message parameters are string literals enclosed in {}
, while
message expressions are string literals enclosed in ${}
. The following algorithm is applied during
method interpolation:
-
Resolve any message parameters by using them as key for the resource bundle ValidationMessages. If this bundle contains an entry for a given message parameter, that parameter will be replaced in the message with the corresponding value from the bundle. This step will be executed recursively in case the replaced value again contains message parameters. The resource bundle is expected to be provided by the application developer, e.g. by adding a file named ValidationMessages.properties to the classpath. You can also create localized error messages by providing locale specific variations of this bundle, such as ValidationMessages_en_US.properties. By default, the JVM’s default locale (
Locale#getDefault()
) will be used when looking up messages in the bundle. -
Resolve any message parameters by using them as key for a resource bundle containing the standard error messages for the built-in constraints as defined in Appendix B of the Bean Validation specification. In the case of Hibernate Validator, this bundle is named
org.hibernate.validator.ValidationMessages
. If this step triggers a replacement, step 1 is executed again, otherwise step 3 is applied. -
Resolve any message parameters by replacing them with the value of the constraint annotation member of the same name. This allows to refer to attribute values of the constraint (e.g.
Size#min()
) in the error message (e.g. "must be at least ${min}"). -
Resolve any message expressions by evaluating them as expressions of the Unified Expression Language. See Interpolation with message expressions to learn more about the usage of Unified EL in error messages.
You can find the formal definition of the interpolation algorithm in section 5.3.1.1 of the Bean Validation specification. |
4.1.1. Special characters
Since the characters {
, }
and $
have a special meaning in message descriptors they need to be escaped if you want to use them literally. The following rules apply:
-
\{
is considered as the literal{
-
\}
is considered as the literal}
-
\$
is considered as the literal$
-
\\
is considered as the literal\
4.1.2. Interpolation with message expressions
As of Hibernate Validator 5 (Bean Validation 1.1) it is possible to use the Unified Expression Language (as defined by JSR 341) in constraint violation messages. This allows to define error messages based on conditional logic and also enables advanced formatting options. The validation engine makes the following objects available in the EL context:
-
the attribute values of the constraint mapped to the attribute names
-
the currently validated value (property, bean, method parameter etc.) under the name validatedValue
-
a bean mapped to the name formatter exposing the var-arg method
format(String format, Object… args)
which behaves likejava.util.Formatter.format(String format, Object… args)
.
The following section provides several examples for using EL expressions in error messages.
4.1.3. Examples
Specifying message descriptors shows how to make use of the different options for specifying message descriptors.
package org.hibernate.validator.referenceguide.chapter04.complete;
public class Car {
@NotNull
private String manufacturer;
@Size(
min = 2,
max = 14,
message = "The license plate '${validatedValue}' must be between {min} and {max} characters long"
)
private String licensePlate;
@Min(
value = 2,
message = "There must be at least {value} seat${value > 1 ? 's' : ''}"
)
private int seatCount;
@DecimalMax(
value = "350",
message = "The top speed ${formatter.format('%1$.2f', validatedValue)} is higher " +
"than {value}"
)
private double topSpeed;
@DecimalMax(value = "100000", message = "Price must not be higher than ${value}")
private BigDecimal price;
public Car(
String manufacturer,
String licensePlate,
int seatCount,
double topSpeed,
BigDecimal price) {
this.manufacturer = manufacturer;
this.licensePlate = licensePlate;
this.seatCount = seatCount;
this.topSpeed = topSpeed;
this.price = price;
}
//getters and setters ...
}
Validating an invalid Car
instance yields constraint violations with the messages shown by the
assertions in Expected error messages:
-
the
@NotNull
constraint on themanufacturer
field causes the error message "may not be null", as this is the default message defined by the Bean Validation specification and no specific descriptor is given in the message attribute -
the
@Size
constraint on thelicensePlate
field shows the interpolation of message parameters ({min}
,{max}
) and how to add the validated value to the error message using the EL expression${validatedValue}
-
the
@Min
constraint onseatCount
demonstrates how use an EL expression with a ternery expression to dynamically chose singular or plural form, depending on an attribute of the constraint ("There must be at least 1 seat" vs. "There must be at least 2 seats") -
the message for the
@DecimalMax
constraint ontopSpeed
shows how to format the validated value using the formatter instance -
finally, the
@DecimalMax
constraint on price shows that parameter interpolation has precedence over expression evaluation, causing the$
sign to show up in front of the maximum price
Only actual constraint attributes can be interpolated using message parameters in the form
|
Car car = new Car( null, "A", 1, 400.123456, BigDecimal.valueOf( 200000 ) );
String message = validator.validateProperty( car, "manufacturer" )
.iterator()
.next()
.getMessage();
assertEquals( "may not be null", message );
message = validator.validateProperty( car, "licensePlate" )
.iterator()
.next()
.getMessage();
assertEquals(
"The license plate 'A' must be between 2 and 14 characters long",
message
);
message = validator.validateProperty( car, "seatCount" ).iterator().next().getMessage();
assertEquals( "There must be at least 2 seats", message );
message = validator.validateProperty( car, "topSpeed" ).iterator().next().getMessage();
assertEquals( "The top speed 400.12 is higher than 350", message );
message = validator.validateProperty( car, "price" ).iterator().next().getMessage();
assertEquals( "Price must not be higher than $100000", message );
4.2. Custom message interpolation
If the default message interpolation algorithm does not fit your requirements it is also possible to
plug in a custom MessageInterpolator
implementation.
Custom interpolators must implement the interface javax.validation.MessageInterpolator
. Note that
implementations must be thread-safe. It is recommended that custom message interpolators delegate
final implementation to the default interpolator, which can be obtained via
Configuration#getDefaultMessageInterpolator()
.
In order to use a custom message interpolator it must be registered either by configuring it in the
Bean Validation XML descriptor META-INF/validation.xml (see
Configuring the validator factory in validation.xml) or by passing it when bootstrapping a ValidatorFactory
or
Validator
(see MessageInterpolator
and
Configuring a Validator, respectively).
4.2.1. ResourceBundleLocator
In some use cases you want to use the message interpolation algorithm as defined by the Bean
Validation specification, but retrieve error messages from other resource bundles than
ValidationMessages. In this situation Hibernate Validator’s ResourceBundleLocator
SPI can help.
The default message interpolator in Hibernate Validator, ResourceBundleMessageInterpolator
,
delegates retrieval of resource bundles to that SPI. Using an alternative bundle only requires
passing an instance of PlatformResourceBundleLocator
with the bundle name when bootstrapping the
ValidatorFactory
as shown in Using a specific resource bundle.
Validator validator = Validation.byDefaultProvider()
.configure()
.messageInterpolator(
new ResourceBundleMessageInterpolator(
new PlatformResourceBundleLocator( "MyMessages" )
)
)
.buildValidatorFactory()
.getValidator();
Of course you also could implement a completely different ResourceBundleLocator
, which for instance
returns bundles backed by records in a database. In this case you can obtain the default locator via
HibernateValidatorConfiguration#getDefaultResourceBundleLocator()
, which you e.g. could use as
fall-back for your custom locator.
Besides PlatformResourceBundleLocator
, Hibernate Validator provides another resource bundle locator
implementation out of the box, namely AggregateResourceBundleLocator
, which allows to retrieve error
messages from more than one resource bundle. You could for instance use this implementation in a
multi-module application where you want to have one message bundle per module.
Using AggregateResourceBundleLocator
shows how to use AggregateResourceBundleLocator
.
AggregateResourceBundleLocator
Validator validator = Validation.byDefaultProvider()
.configure()
.messageInterpolator(
new ResourceBundleMessageInterpolator(
new AggregateResourceBundleLocator(
Arrays.asList(
"MyMessages",
"MyOtherMessages"
)
)
)
)
.buildValidatorFactory()
.getValidator();
Note that the bundles are processed in the order as passed to the constructor. That means if several bundles contain an entry for a given message key, the value will be taken from the first bundle in the list containing the key.
5. Grouping constraints
All validation methods on Validator
and ExecutableValidator
discussed in earlier chapters also take
a var-arg argument groups. So far we have been ignoring this parameter, but it is time to have a
closer look.
5.1. Requesting groups
Groups allow you to restrict the set of constraints applied during validation. One use case for validation groups are UI wizards where in each step only a specified subset of constraints should get validated. The groups targeted are passed as var-arg parameters to the appropriate validate method.
Let’s have a look at an example. The class Person
in Example class Person
has a @NotNull
constraint on name
. Since no group is specified for this annotation the default group
javax.validation.groups.Default
is assumed.
When more than one group is requested, the order in which the groups are evaluated is not
deterministic. If no group is specified the default group |
Person
package org.hibernate.validator.referenceguide.chapter05;
public class Person {
@NotNull
private String name;
public Person(String name) {
this.name = name;
}
// getters and setters ...
}
The class Driver
in Driver extends Person
and adds the properties age
and
hasDrivingLicense
. Drivers must be at least 18 years old (@Min(18)
) and have a driving license
(@AssertTrue
). Both constraints defined on these properties belong to the group DriverChecks
which
is just a simple tagging interface.
Using interfaces makes the usage of groups type-safe and allows for easy refactoring. It also means that groups can inherit from each other via class inheritance. See Group inheritance. |
package org.hibernate.validator.referenceguide.chapter05;
public class Driver extends Person {
@Min(
value = 18,
message = "You have to be 18 to drive a car",
groups = DriverChecks.class
)
public int age;
@AssertTrue(
message = "You first have to pass the driving test",
groups = DriverChecks.class
)
public boolean hasDrivingLicense;
public Driver(String name) {
super( name );
}
public void passedDrivingTest(boolean b) {
hasDrivingLicense = b;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
package org.hibernate.validator.referenceguide.chapter05;
public interface DriverChecks {
}
Finally the class Car
(Car) has some constraints which are part of the default group as
well as @AssertTrue
in the group CarChecks
on the property passedVehicleInspection
which indicates
whether a car passed the road worthy tests.
package org.hibernate.validator.referenceguide.chapter05;
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
@Min(2)
private int seatCount;
@AssertTrue(
message = "The car has to pass the vehicle inspection first",
groups = CarChecks.class
)
private boolean passedVehicleInspection;
@Valid
private Driver driver;
public Car(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}
public boolean isPassedVehicleInspection() {
return passedVehicleInspection;
}
public void setPassedVehicleInspection(boolean passedVehicleInspection) {
this.passedVehicleInspection = passedVehicleInspection;
}
public Driver getDriver() {
return driver;
}
public void setDriver(Driver driver) {
this.driver = driver;
}
// getters and setters ...
}
package org.hibernate.validator.referenceguide.chapter05;
public interface CarChecks {
}
Overall three different groups are used in the example:
-
The constraints on
Person.name
,Car.manufacturer
,Car.licensePlate
andCar.seatCount
all belong to theDefault
group -
The constraints on
Driver.age
andDriver.hasDrivingLicense
belong toDriverChecks
-
The constraint on
Car.passedVehicleInspection
belongs to the groupCarChecks
Using validation groups shows how passing different group combinations to the Validator#validate()
method results in different validation results.
// create a car and check that everything is ok with it.
Car car = new Car( "Morris", "DD-AB-123", 2 );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 0, constraintViolations.size() );
// but has it passed the vehicle inspection?
constraintViolations = validator.validate( car, CarChecks.class );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"The car has to pass the vehicle inspection first",
constraintViolations.iterator().next().getMessage()
);
// let's go to the vehicle inspection
car.setPassedVehicleInspection( true );
assertEquals( 0, validator.validate( car, CarChecks.class ).size() );
// now let's add a driver. He is 18, but has not passed the driving test yet
Driver john = new Driver( "John Doe" );
john.setAge( 18 );
car.setDriver( john );
constraintViolations = validator.validate( car, DriverChecks.class );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"You first have to pass the driving test",
constraintViolations.iterator().next().getMessage()
);
// ok, John passes the test
john.passedDrivingTest( true );
assertEquals( 0, validator.validate( car, DriverChecks.class ).size() );
// just checking that everything is in order now
assertEquals( 0,
validator.validate(
car,
Default.class,
CarChecks.class,
DriverChecks.class
).size()
);
The first validate()
call in Using validation groups is done using no explicit group. There are no
validation errors, even though the property passedVehicleInspection
is per default false
. However,
the constraint defined on this property does not belong to the default group.
The next validation using the CarChecks
group fails until the car passes the vehicle inspection.
Adding a driver to the car and validating against DriverChecks
again yields one constraint violation
due to the fact that the driver has not yet passed the driving test. Only after setting
passedDrivingTest
to true
the validation against DriverChecks
passes.
The last validate()
call finally shows that all constraints are passing by validating against all
defined groups.
5.2. Group inheritance
In Using validation groups, we need to call validate()
for each validation group, or specify all of
them one by one.
In some situations, you may want to define a group of constraints which includes another group. You can do that using group inheritance.
In SuperCar, we define a SuperCar
and a group RaceCarChecks
that extends the Default
group.
A SuperCar
must have safety belts to be allowed to run in races.
package org.hibernate.validator.referenceguide.chapter05.groupinheritance;
public class SuperCar extends Car {
@AssertTrue(
message = "Race car must have a safety belt",
groups = RaceCarChecks.class
)
private boolean safetyBelt;
// getters and setters ...
}
package org.hibernate.validator.referenceguide.chapter05.groupinheritance;
import javax.validation.groups.Default;
public interface RaceCarChecks extends Default {
}
In the example below, we will check if a SuperCar
with one seat and no security belts is a valid car
and if it is a valid race-car.
// create a supercar and check that it's valid as a generic Car
SuperCar superCar = new SuperCar( "Morris", "DD-AB-123", 1 );
assertEquals( "must be greater than or equal to 2", validator.validate( superCar ).iterator().next().getMessage() );
// check that this supercar is valid as generic car and also as race car
Set<ConstraintViolation<SuperCar>> constraintViolations = validator.validate( superCar, RaceCarChecks.class );
assertThat( constraintViolations ).extracting( "message" ).containsOnly(
"Race car must have a safety belt",
"must be greater than or equal to 2"
);
On the first call to validate()
, we do not specify a group. There is one validation error because a
car must have at least one seat. It is the constraint from the Default
group.
On the second call, we specify only the group RaceCarChecks
. There are two validation errors: one
about the missing seat from the Default
group, another one about the fact that there is no safety
belts coming from the RaceCarChecks
group.
5.3. Defining group sequences
By default, constraints are evaluated in no particular order, regardless of which groups they belong to. In some situations, however, it is useful to control the order constraints are evaluated.
In the example from Using validation groups it could for instance be required that first all default car constraints are passing before checking the road worthiness of the car. Finally, before driving away, the actual driver constraints should be checked.
In order to implement such a validation order you just need to define an interface and annotate it
with @GroupSequence
, defining the order in which the groups have to be validated (see
Defining a group sequence). If at least one constraint fails in a sequenced group none of the
constraints of the following groups in the sequence get validated.
package org.hibernate.validator.referenceguide.chapter05;
import javax.validation.GroupSequence;
import javax.validation.groups.Default;
@GroupSequence({ Default.class, CarChecks.class, DriverChecks.class })
public interface OrderedChecks {
}
Groups defining a sequence and groups composing a sequence must not be involved in a cyclic
dependency either directly or indirectly, either through cascaded sequence definition or group
inheritance. If a group containing such a circularity is evaluated, a |
You then can use the new sequence as shown in in Using a group sequence.
Car car = new Car( "Morris", "DD-AB-123", 2 );
car.setPassedVehicleInspection( true );
Driver john = new Driver( "John Doe" );
john.setAge( 18 );
john.passedDrivingTest( true );
car.setDriver( john );
assertEquals( 0, validator.validate( car, OrderedChecks.class ).size() );
5.4. Redefining the default group sequence
5.4.1. @GroupSequence
Besides defining group sequences, the @GroupSequence
annotation also allows to redefine the default
group for a given class. To do so, just add the @GroupSequence
annotation to the class and specify
the sequence of groups which substitute Default for this class within the annotation.
Class RentalCar
with redefined default group introduces a new class RentalCar
with a redefined default group.
RentalCar
with redefined default grouppackage org.hibernate.validator.referenceguide.chapter05;
@GroupSequence({ RentalChecks.class, CarChecks.class, RentalCar.class })
public class RentalCar extends Car {
@AssertFalse(message = "The car is currently rented out", groups = RentalChecks.class)
private boolean rented;
public RentalCar(String manufacturer, String licencePlate, int seatCount) {
super( manufacturer, licencePlate, seatCount );
}
public boolean isRented() {
return rented;
}
public void setRented(boolean rented) {
this.rented = rented;
}
}
package org.hibernate.validator.referenceguide.chapter05;
public interface RentalChecks {
}
With this definition you can evaluate the constraints belonging to RentalChecks
, CarChecks
and
RentalCar
by just requesting the Default
group as seen in Validating an object with redefined default group.
RentalCar rentalCar = new RentalCar( "Morris", "DD-AB-123", 2 );
rentalCar.setPassedVehicleInspection( true );
rentalCar.setRented( true );
Set<ConstraintViolation<RentalCar>> constraintViolations = validator.validate( rentalCar );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"Wrong message",
"The car is currently rented out",
constraintViolations.iterator().next().getMessage()
);
rentalCar.setRented( false );
constraintViolations = validator.validate( rentalCar );
assertEquals( 0, constraintViolations.size() );
Since there must no cyclic dependency in the group and group sequence definitions one cannot just
add |
The Default
group sequence overriding is local to the class it is defined on and is not propagated
to associated objects. For the example this means that adding DriverChecks
to the default group
sequence of RentalCar
would not have any effects. Only the group Default
will be propagated to the
driver association.
Note that you can control the propagated group(s) by declaring a group conversion rule (see Group conversion).
5.4.2. @GroupSequenceProvider
In addition to statically redefining default group sequences via @GroupSequence
, Hibernate Validator
also provides an SPI for the dynamic redefinition of default group sequences depending on the object
state.
For that purpose you need to implement the interface DefaultGroupSequenceProvider
and register this
implementation with the target class via the @GroupSequenceProvider
annotation. In the rental car
scenario you could for instance dynamically add the CarChecks
as seen in
Implementing and using a default group sequence provider.
package org.hibernate.validator.referenceguide.chapter05.groupsequenceprovider;
public class RentalCarGroupSequenceProvider
implements DefaultGroupSequenceProvider<RentalCar> {
@Override
public List<Class<?>> getValidationGroups(RentalCar car) {
List<Class<?>> defaultGroupSequence = new ArrayList<Class<?>>();
defaultGroupSequence.add( RentalCar.class );
if ( car != null && !car.isRented() ) {
defaultGroupSequence.add( CarChecks.class );
}
return defaultGroupSequence;
}
}
package org.hibernate.validator.referenceguide.chapter05.groupsequenceprovider;
@GroupSequenceProvider(RentalCarGroupSequenceProvider.class)
public class RentalCar extends Car {
@AssertFalse(message = "The car is currently rented out", groups = RentalChecks.class)
private boolean rented;
public RentalCar(String manufacturer, String licencePlate, int seatCount) {
super( manufacturer, licencePlate, seatCount );
}
public boolean isRented() {
return rented;
}
public void setRented(boolean rented) {
this.rented = rented;
}
}
5.5. Group conversion
What if you wanted to validate the car related checks together with the driver checks? Of course you
could pass the required groups to the validate call explicitly, but what if you wanted to make these
validations occur as part of the Default
group validation? Here @ConvertGroup
comes into play which
allows you during cascaded validation to use a different group than the originally requested one.
Let’s have a look at @ConvertGroup
usage. Here @GroupSequence({
CarChecks.class, Car.class })
is used to combine the car related constraints under the Default
group
(see Redefining the default group sequence). There is also a @ConvertGroup(from = Default.class, to =
DriverChecks.class)
which ensures the Default
group gets converted to the DriverChecks
group during
cascaded validation of the driver association.
@ConvertGroup
usagepackage org.hibernate.validator.referenceguide.chapter05.groupconversion;
public class Driver {
@NotNull
private String name;
@Min(
value = 18,
message = "You have to be 18 to drive a car",
groups = DriverChecks.class
)
public int age;
@AssertTrue(
message = "You first have to pass the driving test",
groups = DriverChecks.class
)
public boolean hasDrivingLicense;
public Driver(String name) {
this.name = name;
}
public void passedDrivingTest(boolean b) {
hasDrivingLicense = b;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
// getters and setters ...
}
package org.hibernate.validator.referenceguide.chapter05.groupconversion;
@GroupSequence({ CarChecks.class, Car.class })
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
@Min(2)
private int seatCount;
@AssertTrue(
message = "The car has to pass the vehicle inspection first",
groups = CarChecks.class
)
private boolean passedVehicleInspection;
@Valid
@ConvertGroup(from = Default.class, to = DriverChecks.class)
private Driver driver;
public Car(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}
public boolean isPassedVehicleInspection() {
return passedVehicleInspection;
}
public void setPassedVehicleInspection(boolean passedVehicleInspection) {
this.passedVehicleInspection = passedVehicleInspection;
}
public Driver getDriver() {
return driver;
}
public void setDriver(Driver driver) {
this.driver = driver;
}
// getters and setters ...
}
As a result the validation in Test case for @ConvertGroup
succeeds, even though the constraint
on hasDrivingLicense
belongs to the DriverChecks
group and only the Default
group is requested in
the validate()
call.
@ConvertGroup
// create a car and validate. The Driver is still null and does not get validated
Car car = new Car( "VW", "USD-123", 4 );
car.setPassedVehicleInspection( true );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 0, constraintViolations.size() );
// create a driver who has not passed the driving test
Driver john = new Driver( "John Doe" );
john.setAge( 18 );
// now let's add a driver to the car
car.setDriver( john );
constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"The driver constraint should also be validated as part of the default group",
constraintViolations.iterator().next().getMessage(),
"You first have to pass the driving test"
);
You can define group conversions wherever @Valid
can be used, namely associations as well as method
and constructor parameters and return values. Multiple conversions can be specified using
@ConvertGroup.List
.
However, the following restrictions apply:
-
@ConvertGroup
must only be used in combination with@Valid
. If used without, aConstraintDeclarationException
is thrown. -
It is not legal to have multiple conversion rules on the same element with the same from value. In this case, a
ConstraintDeclarationException
is raised. -
The from attribute must not refer to a group sequence. A
ConstraintDeclarationException
is raised in this situation.
Rules are not executed recursively. The first matching conversion rule is used and subsequent rules
are ignored. For example if a set of |
6. Creating custom constraints
The Bean Validation API defines a whole set of standard constraint annotations such as @NotNull
,
@Size
etc. In cases where these built-in constraints are not sufficient, you can easily create
custom constraints tailored to your specific validation requirements.
6.1. Creating a simple constraint
To create a custom constraint, the following three steps are required:
-
Create a constraint annotation
-
Implement a validator
-
Define a default error message
6.1.1. The constraint annotation
This section shows how to write a constraint annotation which can be used to ensure that a given
string is either completely upper case or lower case. Later on this constraint will be applied to
the licensePlate
field of the Car
class from Getting started to ensure, that
the field is always an upper-case string.
The first thing needed is a way to express the two case modes. While you could use String
constants,
a better approach is using a Java 5 enum for that purpose:
CaseMode
to express upper vs. lower casepackage org.hibernate.validator.referenceguide.chapter06;
public enum CaseMode {
UPPER,
LOWER;
}
The next step is to define the actual constraint annotation. If you’ve never designed an annotation before, this may look a bit scary, but actually it’s not that hard:
@CheckCase
constraint annotationpackage org.hibernate.validator.referenceguide.chapter06;
@Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = CheckCaseValidator.class)
@Documented
public @interface CheckCase {
String message() default "{org.hibernate.validator.referenceguide.chapter06.CheckCase." +
"message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
CaseMode value();
@Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Documented
@interface List {
CheckCase[] value();
}
}
An annotation type is defined using the @interface
keyword. All attributes of an annotation type are
declared in a method-like manner. The specification of the Bean Validation API demands, that any
constraint annotation defines
-
an attribute
message
that returns the default key for creating error messages in case the constraint is violated -
an attribute
groups
that allows the specification of validation groups, to which this constraint belongs (see Grouping constraints). This must default to an empty array of type Class<?>. -
an attribute
payload
that can be used by clients of the Bean Validation API to assign custom payload objects to a constraint. This attribute is not used by the API itself. An example for a custom payload could be the definition of a severity:public class Severity { public interface Info extends Payload { } public interface Error extends Payload { } }
public class ContactDetails { @NotNull(message = "Name is mandatory", payload = Severity.Error.class) private String name; @NotNull(message = "Phone number not specified, but not mandatory", payload = Severity.Info.class) private String phoneNumber; // ... }
Now a client can after the validation of a
ContactDetails
instance access the severity of a constraint usingConstraintViolation.getConstraintDescriptor().getPayload()
and adjust its behavior depending on the severity.
Besides these three mandatory attributes there is another one, value
, allowing for the required case
mode to be specified. The name value
is a special one, which can be omitted when using the
annotation, if it is the only attribute specified, as e.g. in @CheckCase(CaseMode.UPPER)
.
In addition, the constraint annotation is decorated with a couple of meta annotations:
-
@Target({ FIELD, METHOD, PARAMETER, ANNOTATION_TYPE})
: Defines the supported target element types for the constraint.@CheckCase
may be used on fields (element typeFIELD
), JavaBeans properties as well as method return values (METHOD
) and method/constructor parameters (PARAMETER
). The element typeANNOTATION_TYPE
allows for the creation of composed constraints (see Constraint composition) based on@CheckCase
.When creating a class-level constraint (see Class-level constraints), the element type
TYPE
would have to be used. Constraints targeting the return value of a constructor need to support the element typeCONSTRUCTOR
. Cross-parameter constraints (see Cross-parameter constraints) which are used to validate all the parameters of a method or constructor together, must supportMETHOD
orCONSTRUCTOR
, respectively. -
@Retention(RUNTIME)
: Specifies, that annotations of this type will be available at runtime by the means of reflection -
@Constraint(validatedBy = CheckCaseValidator.class)
: Marks the annotation type as constraint annotation and specifies the validator to be used to validate elements annotated with@CheckCase
. If a constraint may be used on several data types, several validators may be specified, one for each data type. -
@Documented
: Says, that the use of@CheckCase
will be contained in the JavaDoc of elements annotated with it
Finally, there is an inner annotation type named List
. This annotation allows to specify several
@CheckCase
annotations on the same element, e.g. with different validation groups and messages.
While also another name could be used, the Bean Validation specification recommends to use the name
List
and make the annotation an inner annotation of the corresponding constraint type.
6.1.2. The constraint validator
Having defined the annotation, you need to create a constraint validator, which is able to validate
elements with a @CheckCase
annotation. To do so, implement the interface ConstraintValidator
as
shown below:
@CheckCase
package org.hibernate.validator.referenceguide.chapter06;
public class CheckCaseValidator implements ConstraintValidator<CheckCase, String> {
private CaseMode caseMode;
@Override
public void initialize(CheckCase constraintAnnotation) {
this.caseMode = constraintAnnotation.value();
}
@Override
public boolean isValid(String object, ConstraintValidatorContext constraintContext) {
if ( object == null ) {
return true;
}
if ( caseMode == CaseMode.UPPER ) {
return object.equals( object.toUpperCase() );
}
else {
return object.equals( object.toLowerCase() );
}
}
}
The ConstraintValidator
interface defines two type parameters which are set in the implementation.
The first one specifies the annotation type to be validated (CheckCase
), the second one the type of
elements, which the validator can handle (String
). In case a constraint supports several data types,
a ConstraintValidator
for each allowed type has to be implemented and registered at the constraint
annotation as shown above.
The implementation of the validator is straightforward. The initialize()
method gives you access to
the attribute values of the validated constraint and allows you to store them in a field of the
validator as shown in the example.
The isValid()
method contains the actual validation logic. For @CheckCase
this is the check whether
a given string is either completely lower case or upper case, depending on the case mode retrieved
in initialize()
. Note that the Bean Validation specification recommends to consider null values as
being valid. If null
is not a valid value for an element, it should be annotated with @NotNull
explicitly.
The ConstraintValidatorContext
Implementing a constraint validator for the constraint @CheckCase
relies on the default error message generation by just returning true
or false
from the isValid()
method. Using the passed ConstraintValidatorContext
object it is possible to either add additional
error messages or completely disable the default error message generation and solely define custom
error messages. The ConstraintValidatorContext
API is modeled as fluent interface and is best
demonstrated with an example:
ConstraintValidatorContext
to define custom error messagespackage org.hibernate.validator.referenceguide.chapter06.constraintvalidatorcontext;
public class CheckCaseValidator implements ConstraintValidator<CheckCase, String> {
private CaseMode caseMode;
@Override
public void initialize(CheckCase constraintAnnotation) {
this.caseMode = constraintAnnotation.value();
}
@Override
public boolean isValid(String object, ConstraintValidatorContext constraintContext) {
if ( object == null ) {
return true;
}
boolean isValid;
if ( caseMode == CaseMode.UPPER ) {
isValid = object.equals( object.toUpperCase() );
}
else {
isValid = object.equals( object.toLowerCase() );
}
if ( !isValid ) {
constraintContext.disableDefaultConstraintViolation();
constraintContext.buildConstraintViolationWithTemplate(
"{org.hibernate.validator.referenceguide.chapter06." +
"constraintvalidatorcontext.CheckCase.message}"
)
.addConstraintViolation();
}
return isValid;
}
}
Using ConstraintValidatorContext
to define custom error messages
shows how you can disable the default error message generation and add a custom error message using
a specified message template. In this example the use of the ConstraintValidatorContext
results in
the same error message as the default error message generation.
It is important to add each configured constraint violation by calling |
Refer to Custom property paths to learn how to use the ConstraintValidatorContext
API to
control the property path of constraint violations for class-level constraints.
6.1.3. The error message
The last missing building block is an error message which should be used in case a @CheckCase
constraint is violated. To define this, create a file ValidationMessages.properties with the
following contents (see also Default message interpolation):
CheckCase
constraintorg.hibernate.validator.referenceguide.chapter06.CheckCase.message=Case mode must be {value}.
If a validation error occurs, the validation runtime will use the default value, that you specified
for the message attribute of the @CheckCase
annotation to look up the error message in this resource
bundle.
6.1.4. Using the constraint
You can now use the constraint in the Car
class from the Getting started chapter to
specify that the licensePlate
field should only contain upper-case strings:
@CheckCase
constraintpackage org.hibernate.validator.referenceguide.chapter06;
public class Car {
@NotNull
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
@CheckCase(CaseMode.UPPER)
private String licensePlate;
@Min(2)
private int seatCount;
public Car(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}
//getters and setters ...
}
Finally, Validating objects with the @CheckCase
constraint demonstrates how validating a Car
instance with an invalid
license plate causes the @CheckCase
constraint to be violated.
@CheckCase
constraint//invalid license plate
Car car = new Car( "Morris", "dd-ab-123", 4 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"Case mode must be UPPER.",
constraintViolations.iterator().next().getMessage()
);
//valid license plate
car = new Car( "Morris", "DD-AB-123", 4 );
constraintViolations = validator.validate( car );
assertEquals( 0, constraintViolations.size() );
6.2. Class-level constraints
As discussed earlier, constraints can also be applied on the class level to validate the state of an
entire object. Class-level constraints are defined in the same was as are property constraints.
Implementing a class-level constraint shows constraint annotation and validator of the
@ValidPassengerCount
constraint you already saw in use in Class-level constraint.
package org.hibernate.validator.referenceguide.chapter06.classlevel;
@Target({ TYPE, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = { ValidPassengerCountValidator.class })
@Documented
public @interface ValidPassengerCount {
String message() default "{org.hibernate.validator.referenceguide.chapter06.classlevel." +
"ValidPassengerCount.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
package org.hibernate.validator.referenceguide.chapter06.classlevel;
public class ValidPassengerCountValidator
implements ConstraintValidator<ValidPassengerCount, Car> {
@Override
public void initialize(ValidPassengerCount constraintAnnotation) {
}
@Override
public boolean isValid(Car car, ConstraintValidatorContext context) {
if ( car == null ) {
return true;
}
return car.getPassengers().size() <= car.getSeatCount();
}
}
As the example demonstrates, you need to use the element type TYPE
in the @Target
annotation. This
allows the constraint to be put on type definitions. The validator of the constraint in the example
receives a Car
in the isValid()
method and can access the complete object state to decide whether
the given instance is valid or not.
6.2.1. Custom property paths
By default the constraint violation for a class-level constraint is reported on the level of the
annotated type, e.g. Car
.
In some cases it is preferable though that the violation’s property path refers to one of the
involved properties. For instance you might want to report the @ValidPassengerCount
constraint
against the passengers property instead of the Car
bean.
Adding a new ConstraintViolation
with custom property path
shows how this can be done by using the constraint validator context passed to isValid()
to build a
custom constraint violation with a property node for the property passengers. Note that you also
could add several property nodes, pointing to a sub-entity of the validated bean.
ConstraintViolation
with custom property pathpackage org.hibernate.validator.referenceguide.chapter06.custompath;
public class ValidPassengerCountValidator
implements ConstraintValidator<ValidPassengerCount, Car> {
@Override
public void initialize(ValidPassengerCount constraintAnnotation) {
}
@Override
public boolean isValid(Car car, ConstraintValidatorContext constraintValidatorContext) {
if ( car == null ) {
return true;
}
boolean isValid = car.getPassengers().size() <= car.getSeatCount();
if ( !isValid ) {
constraintValidatorContext.disableDefaultConstraintViolation();
constraintValidatorContext
.buildConstraintViolationWithTemplate( "{my.custom.template}" )
.addPropertyNode( "passengers" ).addConstraintViolation();
}
return isValid;
}
}
6.3. Cross-parameter constraints
Bean Validation distinguishes between two different kinds of constraints.
Generic constraints (which have been discussed so far) apply to the annotated element, e.g. a type, field, method parameter or return value etc. Cross-parameter constraints, in contrast, apply to the array of parameters of a method or constructor and can be used to express validation logic which depends on several parameter values.
In order to define a cross-parameter constraint, its validator class must be annotated with
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
. The type parameter T
from the
ConstraintValidator
interface must resolve to either Object
or Object[]
in order to receive the
array of method/constructor arguments in the isValid()
method.
The following example shows the definition of a cross-parameter constraint which can be used to
check that two Date
parameters of a method are in the correct order:
package org.hibernate.validator.referenceguide.chapter06.crossparameter;
@Constraint(validatedBy = ConsistentDateParametersValidator.class)
@Target({ METHOD, CONSTRUCTOR, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Documented
public @interface ConsistentDateParameters {
String message() default "{org.hibernate.validator.referenceguide.chapter04." +
"crossparameter.ConsistentDateParameters.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
The definition of a cross-parameter constraint isn’t any different from defining a generic
constraint, i.e. it must specify the members message()
, groups()
and payload()
and be annotated with
@Constraint
. This meta annotation also specifies the corresponding validator, which is shown in
Generic and cross-parameter constraint. Note that besides the element types METHOD
and CONSTRUCTOR
also ANNOTATION_TYPE
is specified as target of the annotation, in order to enable the creation of
composed constraints based on @ConsistentDateParameters
(see
Constraint composition).
Cross-parameter constraints are specified directly on the declaration of a method or constructor,
which is also the case for return value constraints. In order to improve code readability, it is
therefore recommended to chose constraint names - such as |
package org.hibernate.validator.referenceguide.chapter06.crossparameter;
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class ConsistentDateParametersValidator implements
ConstraintValidator<ConsistentDateParameters, Object[]> {
@Override
public void initialize(ConsistentDateParameters constraintAnnotation) {
}
@Override
public boolean isValid(Object[] value, ConstraintValidatorContext context) {
if ( value.length != 2 ) {
throw new IllegalArgumentException( "Illegal method signature" );
}
//leave null-checking to @NotNull on individual parameters
if ( value[0] == null || value[1] == null ) {
return true;
}
if ( !( value[0] instanceof Date ) || !( value[1] instanceof Date ) ) {
throw new IllegalArgumentException(
"Illegal method signature, expected two " +
"parameters of type Date."
);
}
return ( (Date) value[0] ).before( (Date) value[1] );
}
}
As discussed above, the validation target PARAMETERS
must be configured for a cross-parameter
validator by using the @SupportedValidationTarget
annotation. Since a cross-parameter constraint
could be applied to any method or constructor, it is considered a best practice to check for the
expected number and types of parameters in the validator implementation.
As with generic constraints, null
parameters should be considered valid and @NotNull
on the
individual parameters should be used to make sure that parameters are not null
.
Similar to class-level constraints, you can create custom constraint violations on single parameters
instead of all parameters when validating a cross-parameter constraint. Just obtain a node builder
from the |
In rare situations a constraint is both, generic and cross-parameter. This is the case if a
constraint has a validator class which is annotated with
@SupportedValidationTarget({ValidationTarget.PARAMETERS, ValidationTarget.ANNOTATED_ELEMENT})
or if
it has a generic and a cross-parameter validator class.
When declaring such a constraint on a method which has parameters and also a return value, the
intended constraint target can’t be determined. Constraints which are generic and cross-parameter at
the same time, must therefore define a member validationAppliesTo()
which allows the constraint user
to specify the constraint’s target as shown in Generic and cross-parameter constraint.
package org.hibernate.validator.referenceguide.chapter06.crossparameter;
@Constraint(validatedBy = {
ScriptAssertObjectValidator.class,
ScriptAssertParametersValidator.class
})
@Target({ TYPE, FIELD, PARAMETER, METHOD, CONSTRUCTOR, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Documented
public @interface ScriptAssert {
String message() default "{org.hibernate.validator.referenceguide.chapter04." +
"crossparameter.ScriptAssert.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
String script();
ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;
}
The @ScriptAssert
constraint has two validators (not shown), a generic and a cross-parameter one and
thus defines the member validationAppliesTo()
. The default value IMPLICIT
allows to derive the
target automatically in situations where this is possible (e.g. if the constraint is declared on a
field or on a method which has parameters but no return value).
If the target can not be determined implicitly, it must be set by the user to either PARAMETERS
or
RETURN_VALUE
as shown in Specifying the target for a generic and cross-parameter constraint.
@ScriptAssert(script = "arg1.size() <= arg0", validationAppliesTo = ConstraintTarget.PARAMETERS)
public Car buildCar(int seatCount, List<Passenger> passengers) {
//...
return null;
}
6.4. Constraint composition
Looking at the licensePlate
field of the Car
class in Applying the @CheckCase
constraint, you see three
constraint annotations already. In complexer scenarios, where even more constraints could be applied
to one element, this might become a bit confusing easily. Furthermore, if there was a licensePlate
field in another class, you would have to copy all constraint declarations to the other class as
well, violating the DRY principle.
You can address this kind of problem by creating higher level constraints, composed from several
basic constraints. Creating a composing constraint @ValidLicensePlate
shows a composed constraint annotation which
comprises the constraints @NotNull
, @Size
and @CheckCase
:
@ValidLicensePlate
package org.hibernate.validator.referenceguide.chapter06.constraintcomposition;
@NotNull
@Size(min = 2, max = 14)
@CheckCase(CaseMode.UPPER)
@Target({ METHOD, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = { })
@Documented
public @interface ValidLicensePlate {
String message() default "{org.hibernate.validator.referenceguide.chapter06." +
"constraintcomposition.ValidLicensePlate.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
To create a composed constraint, simply annotate the constraint declaration with its comprising
constraints. If the composed constraint itself requires a validator, this validator is to be
specified within the @Constraint
annotation. For composed constraints which don’t need an additional
validator such as @ValidLicensePlate
, just set validatedBy()
to an empty array.
Using the new composed constraint at the licensePlate
field is fully equivalent to the previous
version, where the three constraints were declared directly at the field itself:
ValidLicensePlate
package org.hibernate.validator.referenceguide.chapter06.constraintcomposition;
public class Car {
@ValidLicensePlate
private String licensePlate;
//...
}
The set of ConstraintViolations
retrieved when validating a Car
instance will contain an entry for
each violated composing constraint of the @ValidLicensePlate
constraint. If you rather prefer a
single ConstraintViolation
in case any of the composing constraints is violated, the
@ReportAsSingleViolation
meta constraint can be used as follows:
package org.hibernate.validator.referenceguide.chapter06.constraintcomposition.reportassingle;
//...
@ReportAsSingleViolation
public @interface ValidLicensePlate {
String message() default "{org.hibernate.validator.referenceguide.chapter06." +
"constraintcomposition.ValidLicensePlate.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
7. Configuring via XML
So far we have used the default configuration source for Bean Validation, namely annotations. However, there also exist two kinds of XML descriptors allowing configuration via XML. The first descriptor describes general Bean Validation behaviour and is provided as META-INF/validation.xml. The second one describes constraint declarations and closely matches the constraint declaration approach via annotations. Let’s have a look at these two document types.
The XSD files are available via http://www.jboss.org/xml/ns/javax/validation/configuration and http://www.jboss.org/xml/ns/javax/validation/mapping. |
7.1. Configuring the validator factory in validation.xml
The key to enable XML configuration for Hibernate Validator is the file META-INF/validation.xml.
If this file exists on the classpath its configuration will be applied when the ValidatorFactory
gets created. Validation configuration schema shows a model view of the XML schema to which
validation.xml has to adhere.
![validation-configuration-1.1.xsd](images/validation-configuration-1.1.png)
validation.xml
shows the several configuration options of validation.xml. All settings are optional and the same
configuration options are also available programmatically through javax.validation.Configuration
. In
fact the XML configuration will be overridden by values explicitly specified via the programmatic
API. It is even possible to ignore the XML configuration completely via
Configuration#ignoreXmlConfiguration()
. See also Configuring a ValidatorFactory
.
validation.xml
<validation-config
xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration">
<default-provider>com.acme.ValidationProvider</default-provider>
<message-interpolator>com.acme.MessageInterpolator</message-interpolator>
<traversable-resolver>com.acme.TraversableResolver</traversable-resolver>
<constraint-validator-factory>
com.acme.ConstraintValidatorFactory
</constraint-validator-factory>
<parameter-name-provider>com.acme.ParameterNameProvider</parameter-name-provider>
<executable-validation enabled="true">
<default-validated-executable-types>
<executable-type>CONSTRUCTORS</executable-type>
<executable-type>NON_GETTER_METHODS</executable-type>
<executable-type>GETTER_METHODS</executable-type>
</default-validated-executable-types>
</executable-validation>
<constraint-mapping>META-INF/validation/constraints-car.xml</constraint-mapping>
<property name="hibernate.validator.fail_fast">false</property>
</validation-config>
There must only be one file named META-INF/validation.xml on the classpath. If more than one is found an exception is thrown. |
The node default-provider
allows to choose the Bean Validation provider. This is useful if there is
more than one provider on the classpath. message-interpolator
, traversable-resolver
,
constraint-validator-factory
and parameter-name-provider
allow to customize the used
implementations for the interfaces MessageInterpolator
, TraversableResolver
,
ConstraintValidatorFactory
and ParameterNameProvider
defined in the javax.validation
package.
See the sub-sections of Configuring a ValidatorFactory
for more information about these
interfaces.
executable-validation
and its subnodes define defaults for method validation. The Bean Validation
specification defines constructor and non getter methods as defaults. The enabled attribute acts as
global switch to turn method validation on and off (see also Declaring and validating method constraints).
Via the constraint-mapping
element you can list an arbitrary number of additional XML files
containing the actual constraint configuration. Mapping file names must be specified using their
fully-qualified name on the classpath. Details on writing mapping files can be found in the next
section.
Last but not least, you can specify provider specific properties via the property
nodes. In the
example we are using the Hibernate Validator specific hibernate.validator.fail_fast
property (see
Fail fast mode).
7.2. Mapping constraints via constraint-mappings
Expressing constraints in XML is possible via files adhering to the schema seen in Validation mapping schema. Note that these mapping files are only processed if listed via constraint-mapping in validation.xml.
![validation-mapping-1.1.xsd](images/validation-mapping-1.1.png)
Bean constraints configured via XML shows how the classes Car and RentalCar from Car resp.
Class RentalCar
with redefined default group could be mapped in XML.
<constraint-mappings
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
xmlns="http://jboss.org/xml/ns/javax/validation/mapping" version="1.1">
<default-package>org.hibernate.validator.referenceguide.chapter05</default-package>
<bean class="Car" ignore-annotations="true">
<field name="manufacturer">
<constraint annotation="javax.validation.constraints.NotNull"/>
</field>
<field name="licensePlate">
<constraint annotation="javax.validation.constraints.NotNull"/>
</field>
<field name="seatCount">
<constraint annotation="javax.validation.constraints.Min">
<element name="value">2</element>
</constraint>
</field>
<field name="driver">
<valid/>
</field>
<getter name="passedVehicleInspection" ignore-annotations="true">
<constraint annotation="javax.validation.constraints.AssertTrue">
<message>The car has to pass the vehicle inspection first</message>
<groups>
<value>CarChecks</value>
</groups>
<element name="max">10</element>
</constraint>
</getter>
</bean>
<bean class="RentalCar" ignore-annotations="true">
<class ignore-annotations="true">
<group-sequence>
<value>RentalCar</value>
<value>CarChecks</value>
</group-sequence>
</class>
</bean>
<constraint-definition annotation="org.mycompany.CheckCase">
<validated-by include-existing-validators="false">
<value>org.mycompany.CheckCaseValidator</value>
</validated-by>
</constraint-definition>
</constraint-mappings>
Method constraints configured via XML shows how the constraints from Declaring method and constructor parameter constraints, Declaring method and constructor return value constraints and Specifying a constraint’s target can be expressed in XML.
<constraint-mappings
xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=
"http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd" version="1.1">
<default-package>org.hibernate.validator.referenceguide.chapter07</default-package>
<bean class="RentalStation" ignore-annotations="true">
<constructor>
<return-value>
<constraint annotation="ValidRentalStation"/>
</return-value>
</constructor>
<constructor>
<parameter type="java.lang.String">
<constraint annotation="javax.validation.constraints.NotNull"/>
</parameter>
</constructor>
<method name="getCustomers">
<return-value>
<constraint annotation="javax.validation.constraints.NotNull"/>
<constraint annotation="javax.validation.constraints.Size">
<element name="min">1</element>
</constraint>
</return-value>
</method>
<method name="rentCar">
<parameter type="Customer">
<constraint annotation="javax.validation.constraints.NotNull"/>
</parameter>
<parameter type="java.util.Date">
<constraint annotation="javax.validation.constraints.NotNull"/>
<constraint annotation="javax.validation.constraints.Future"/>
</parameter>
<parameter type="int">
<constraint annotation="javax.validation.constraints.Min">
<element name="value">1</element>
</constraint>
</parameter>
</method>
</bean>
<bean class="Garage" ignore-annotations="true">
<method name="buildCar">
<parameter type="java.util.List"/>
<cross-parameter>
<constraint annotation="ELAssert">
<element name="expression">...</element>
<element name="validationAppliesTo">PARAMETERS</element>
</constraint>
</cross-parameter>
</method>
<method name="paintCar">
<parameter type="int"/>
<return-value>
<constraint annotation="ELAssert">
<element name="expression">...</element>
<element name="validationAppliesTo">RETURN_VALUE</element>
</constraint>
</return-value>
</method>
</bean>
</constraint-mappings>
The XML configuration is closely mirroring the programmatic API. For this reason it should suffice
to just add some comments. default-package
is used for all fields where a class name is expected. If
the specified class is not fully qualified the configured default package will be used. Every
mapping file can then have several bean nodes, each describing the constraints on the entity with
the specified class name.
A given class can only be configured once across all configuration files. The same applies for
constraint definitions for a given constraint annotation. It can only occur in one mapping file. If
these rules are violated a |
Setting ignore-annotations
to true
means that constraint annotations placed on the configured bean
are ignored. The default for this value is true. ignore-annotations
is also available for the nodes
class
, fields
, getter
, constructor
, method
, parameter
, cross-parameter
and return-value
.
If not explicitly specified on these levels the configured bean value applies.
The nodes class
, field
, getter
, constructor
and method
(and its sub node parameter) determine on
which level the constraint gets placed. The constraint
node is then used to add a constraint on the
corresponding level. Each constraint definition must define the class via the annotation
attribute.
The constraint attributes required by the Bean Validation specification (message
, groups
and
payload
) have dedicated nodes. All other constraint specific attributes are configured using the
element
node.
The class
node also allows to reconfigure the default group sequence (see
Redefining the default group sequence) via the group-sequence
node. Not shown in the example is the use
of convert-group
to
specify group conversions (see Group conversion). This node is available on field
,
getter
, parameter
and return-value
and specifies a from and to attribute to specify the groups.
Last but not least, the list of ConstraintValidator
instances associated to a given constraint
can be altered via the constraint-definition
node. The annotation attribute represents the constraint
annotation being altered. The validated-by
element represent the (ordered) list of ConstraintValidator
implementations associated to the constraint. If include-existing-validator
is set to false
,
validators defined on the constraint annotation are ignored. If set to true
, the list of constraint
validators described in XML is concatenated to the list of validators specified on the annotation.
One use case for constraint-definition is to change the default constraint definition for Using XML to register a regular expression based constraint definition for
@URL
|
8. Bootstrapping
In Obtaining a Validator
instance you already saw one way for creating a Validator instance - via
Validation#buildDefaultValidatorFactory()
. In this chapter you will learn how to use the other
methods in javax.validation.Validation
in order to bootstrap specifically configured validators.
8.1. Retrieving ValidatorFactory
and Validator
You obtain a Validator
by retrieving a ValidatorFactory
via one of the static methods on
javax.validation.Validation
and calling getValidator()
on the factory instance.
Bootstrapping default ValidatorFactory
and Validator
shows how to obtain a validator from the default
validator factory:
ValidatorFactory
and Validator
ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
Validator validator = validatorFactory.getValidator();
The generated |
Bean Validation supports working with several providers such as Hibernate Validator within one
application. If more than one provider is present on the classpath, it is not guaranteed which one
is chosen when creating a factory via buildDefaultValidatorFactory()
.
In this case you can explicitly specify the provider to use via Validation#byProvider()
, passing the
provider’s ValidationProvider
class as shown in Bootstrapping ValidatorFactory
and Validator using a specific provider.
ValidatorFactory
and Validator using a specific providerValidatorFactory validatorFactory = Validation.byProvider( HibernateValidator.class )
.configure()
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Note that the configuration object returned by configure()
allows to specifically customize the
factory before calling buildValidatorFactory()
. The available options are discussed later in this
chapter.
Similarly you can retrieve the default validator factory for configuration which is demonstrated in
Retrieving the default ValidatorFactory
for configuration.
ValidatorFactory
for configurationValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
If a |
8.1.1. ValidationProviderResolver
By default, available Bean Validation providers are discovered using the Java Service Provider mechanism.
For that purpose, each provider includes the file META-
INF/services/javax.validation.spi.ValidationProvider, containing the fully qualified classname of
its ValidationProvider
implementation. In the case of Hibernate Validator this is
org.hibernate.validator.HibernateValidator
.
Depending on your environment and its classloading specifics, provider discovery via the Java’s
service loader mechanism might not work. In this case you can plug in a custom
ValidationProviderResolver
implementation which performs the provider retrieval. An example is OSGi,
where you could implement a provider resolver which uses OSGi services for provider discovery.
To use a custom provider resolver pass it via providerResolver()
as shown shown in
Using a custom ValidationProviderResolver
.
ValidationProviderResolver
package org.hibernate.validator.referenceguide.chapter08;
public class OsgiServiceDiscoverer implements ValidationProviderResolver {
@Override
public List<ValidationProvider<?>> getValidationProviders() {
//...
return null;
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.providerResolver( new OsgiServiceDiscoverer() )
.configure()
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
8.2. Configuring a ValidatorFactory
By default validator factories retrieved from Validation
and any validators they create are
configured as per the XML descriptor META-INF/validation.xml (see Configuring via XML),
if present.
If you want to disable the XML based configuration, you can do so by invoking
Configuration#ignoreXmlConfiguration()
.
The different values of the XML configuration can be accessed via
Configuration#getBootstrapConfiguration()
. This can for instance be helpful if you want to integrate
Bean Validation into a managed environment and want to create managed instances of the objects
configured via XML.
Using the fluent configuration API, you can override one or more of the settings when bootstrapping
the factory. The following sections show how to make use of the different options. Note that the
Configuration
class exposes the default implementations of the different extension points which can
be useful if you want to use these as delegates for your custom implementations.
8.2.1. MessageInterpolator
Message interpolators are used by the validation engine to create user readable error messages from constraint message descriptors.
In case the default message interpolation algorithm described in Interpolating constraint error messages
is not sufficient for your needs, you can pass in your own implementation of the MessageInterpolator
interface via Configuration#messageInterpolator()
as shown in
Using a custom MessageInterpolator
.
MessageInterpolator
package org.hibernate.validator.referenceguide.chapter08;
public class MyMessageInterpolator implements MessageInterpolator {
@Override
public String interpolate(String messageTemplate, Context context) {
//...
return null;
}
@Override
public String interpolate(String messageTemplate, Context context, Locale locale) {
//...
return null;
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.messageInterpolator( new MyMessageInterpolator() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
8.2.2. TraversableResolver
In some cases the validation engine should not access the state of a bean property. The most obvious example for that is a lazily loaded property or association of a JPA entity. Validating this lazy property or association would mean that its state would have to be accessed, triggering a load from the database.
Which properties can be accessed and which ones not is controlled by querying the
TraversableResolver
interface. Using a custom TraversableResolver
shows how to use a
custom traversable resolver implementation.
TraversableResolver
package org.hibernate.validator.referenceguide.chapter08;
public class MyTraversableResolver implements TraversableResolver {
@Override
public boolean isReachable(
Object traversableObject,
Node traversableProperty,
Class<?> rootBeanType,
Path pathToTraversableObject,
ElementType elementType) {
//...
return false;
}
@Override
public boolean isCascadable(
Object traversableObject,
Node traversableProperty,
Class<?> rootBeanType,
Path pathToTraversableObject,
ElementType elementType) {
//...
return false;
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.traversableResolver( new MyTraversableResolver() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
If no specific traversable resolver has been configured, the default behavior is to consider all properties as reachable and cascadable. When using Hibernate Validator together with a JPA 2 provider such as Hibernate ORM, only those properties will be considered reachable which already have been loaded by the persistence provider and all properties will be considered cascadable.
8.2.3. ConstraintValidatorFactory
ConstraintValidatorFactory
is the extension point for customizing how constraint validators are
instantiated and released.
The default ConstraintValidatorFactory
provided by Hibernate Validator requires a public no-arg
constructor to instantiate ConstraintValidator
instances (see The constraint validator).
Using a custom ConstraintValidatorFactory
offers for example the possibility to use dependency
injection in constraint validator implementations.
To configure a custom constraint validator factory call Configuration#constraintValidatorFactory()
(see Using a custom ConstraintValidatorFactory
.
ConstraintValidatorFactory
package org.hibernate.validator.referenceguide.chapter08;
public class MyConstraintValidatorFactory implements ConstraintValidatorFactory {
@Override
public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key) {
//...
return null;
}
@Override
public void releaseInstance(ConstraintValidator<?, ?> instance) {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.constraintValidatorFactory( new MyConstraintValidatorFactory() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Any constraint implementations relying on |
|
8.2.4. ParameterNameProvider
In case a method or constructor parameter constraint is violated, the ParameterNameProvider
interface is used to retrieve the parameter name and make it available to the user via the
property path of the constraint violation.
The default implementation returns parameter names in the form of arg0
, arg1
etc, while custom
implementations can retrieve the parameter names using methods such as parameter annotations,
debug symbols, or Java 8 reflection.
An implementation for retrieving the parameter names using reflection in Java 8 is provided with
ReflectionParameterNameProvider
. For this parameter name provider to work, the
source must be compiled using the –parameters
compiler argument. Otherwise, the provider will
return synthetic names in the form of arg0
, arg1
, etc.
To use ReflectionParameterNameProvider
or another custom provider either pass an instance of
the provider during bootstrapping as shown in Using a custom ParameterNameProvider
,
or specify the fully qualified class name of the provider as value for
the <parameter-name-provider>
element in the META-INF/validation.xml file
(see Configuring the validator factory in validation.xml). This is demonstrated in
Using a custom ParameterNameProvider
.
ParameterNameProvider
package org.hibernate.validator.referenceguide.chapter08;
public class MyParameterNameProvider implements ParameterNameProvider {
@Override
public List<String> getParameterNames(Constructor<?> constructor) {
//...
return null;
}
@Override
public List<String> getParameterNames(Method method) {
//...
return null;
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.parameterNameProvider( new MyParameterNameProvider() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Hibernate Validator comes with a custom |
8.2.5. Adding mapping streams
As discussed earlier you can configure the constraints applying for your Java beans using XML based constraint mappings.
Besides the mapping files specified in META-INF/validation.xml you can add further mappings via
Configuration#addMapping()
(see Adding constraint mapping streams). Note that the passed input
stream(s) must adhere to the XML schema for constraint mappings presented in
Mapping constraints via constraint-mappings
.
InputStream constraintMapping1 = null;
InputStream constraintMapping2 = null;
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.addMapping( constraintMapping1 )
.addMapping( constraintMapping2 )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
You should close any passed input stream after the validator factory has been created.
8.2.6. Provider-specific settings
Via the configuration object returned by Validation#byProvider()
provider specific options can be
configured.
In case of Hibernate Validator this e.g. allows you to enable the fail fast mode and pass one or more programmatic constraint mappings as demonstrated in Setting Hibernate Validator specific options.
ValidatorFactory validatorFactory = Validation.byProvider( HibernateValidator.class )
.configure()
.failFast( true )
.addMapping( (ConstraintMapping) null )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Alternatively, provider-specific options can be passed via Configuration#addProperty()
. Hibernate
Validator supports enabling the fail fast mode that way, too:
addProperty()
ValidatorFactory validatorFactory = Validation.byProvider( HibernateValidator.class )
.configure()
.addProperty( "hibernate.validator.fail_fast", "true" )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Refer to Fail fast mode and Programmatic constraint definition and declaration to learn more about the fail fast mode and the constraint declaration API.
8.3. Configuring a Validator
When working with a configured validator factory it can occasionally be required to apply a
different configuration to a single Validator
instance. Configuring a Validator
instance via usingContext()
shows how this can
be achieved by calling ValidatorFactory#usingContext()
.
Validator
instance via usingContext()
ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
Validator validator = validatorFactory.usingContext()
.messageInterpolator( new MyMessageInterpolator() )
.traversableResolver( new MyTraversableResolver() )
.getValidator();
9. Using constraint metadata
The Bean Validation specification provides not only a validation engine, but also an API for
retrieving constraint metadata in a uniform way, no matter whether the constraints are declared
using annotations or via XML mappings. Read this chapter to learn more about this API and its
possibilities. You can find all the metadata API types in the package javax.validation.metadata
.
The examples presented in this chapter are based on the classes and constraint declarations shown in Example classes.
package org.hibernate.validator.referenceguide.chapter09;
public class Person {
public interface Basic {
}
@NotNull
private String name;
//getters and setters ...
}
package org.hibernate.validator.referenceguide.chapter09;
public interface Vehicle {
public interface Basic {
}
@NotNull(groups = Vehicle.Basic.class)
String getManufacturer();
}
package org.hibernate.validator.referenceguide.chapter09;
@ValidCar
public class Car implements Vehicle {
public interface SeverityInfo extends Payload {
}
private String manufacturer;
@NotNull
@Size(min = 2, max = 14)
private String licensePlate;
private Person driver;
private String modelName;
public Car() {
}
public Car(
@NotNull String manufacturer,
String licencePlate,
Person driver,
String modelName) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.driver = driver;
this.modelName = modelName;
}
public void driveAway(@Max(75) int speed) {
//...
}
@LuggageCountMatchesPassengerCount(
piecesOfLuggagePerPassenger = 2,
validationAppliesTo = ConstraintTarget.PARAMETERS,
payload = SeverityInfo.class,
message = "There must not be more than {piecesOfLuggagePerPassenger} pieces " +
"of luggage per passenger."
)
public void load(List<Person> passengers, List<PieceOfLuggage> luggage) {
//...
}
@Override
@Size(min = 3)
public String getManufacturer() {
return manufacturer;
}
public void setManufacturer(String manufacturer) {
this.manufacturer = manufacturer;
}
@Valid
@ConvertGroup(from = Default.class, to = Person.Basic.class)
public Person getDriver() {
return driver;
}
//further getters and setters...
}
9.1. BeanDescriptor
The entry point into the metadata API is the method Validator#getConstraintsForClass()
, which
returns an instance of the BeanDescriptor
interface. Using this
descriptor, you can obtain metadata for constraints declared directly on the bean itself (class- or
property-level), but also retrieve metadata descriptors representing single properties, methods and
constructors.
Using BeanDescriptor
demonstrates how to retrieve a BeanDescriptor
for the
Car
class and how to use this descriptor in form of assertions.
If a constraint declaration hosted by the requested class is invalid, a |
BeanDescriptor
BeanDescriptor carDescriptor = validator.getConstraintsForClass( Car.class );
assertTrue( carDescriptor.isBeanConstrained() );
//one class-level constraint
assertEquals( 1, carDescriptor.getConstraintDescriptors().size() );
//manufacturer, licensePlate, driver
assertEquals( 3, carDescriptor.getConstrainedProperties().size() );
//property has constraint
assertNotNull( carDescriptor.getConstraintsForProperty( "licensePlate" ) );
//property is marked with @Valid
assertNotNull( carDescriptor.getConstraintsForProperty( "driver" ) );
//constraints from getter method in interface and implementation class are returned
assertEquals(
2,
carDescriptor.getConstraintsForProperty( "manufacturer" )
.getConstraintDescriptors()
.size()
);
//property is not constrained
assertNull( carDescriptor.getConstraintsForProperty( "modelName" ) );
//driveAway(int), load(List<Person>, List<PieceOfLuggage>)
assertEquals( 2, carDescriptor.getConstrainedMethods( MethodType.NON_GETTER ).size() );
//driveAway(int), getManufacturer(), getDriver(), load(List<Person>, List<PieceOfLuggage>)
assertEquals(
4,
carDescriptor.getConstrainedMethods( MethodType.NON_GETTER, MethodType.GETTER )
.size()
);
//driveAway(int)
assertNotNull( carDescriptor.getConstraintsForMethod( "driveAway", int.class ) );
//getManufacturer()
assertNotNull( carDescriptor.getConstraintsForMethod( "getManufacturer" ) );
//setManufacturer() is not constrained
assertNull( carDescriptor.getConstraintsForMethod( "setManufacturer", String.class ) );
//Car(String, String, Person, String)
assertEquals( 1, carDescriptor.getConstrainedConstructors().size() );
//Car(String, String, Person, String)
assertNotNull(
carDescriptor.getConstraintsForConstructor(
String.class,
String.class,
Person.class,
String.class
)
);
You can determine whether the specified class hosts any class- or property-level constraints via
isBeanConstrained()
. Method or constructor constraints are not considered by isBeanConstrained()
.
The method getConstraintDescriptors()
is common to all descriptors derived from ElementDescriptor
(see ElementDescriptor
) and returns a set of descriptors representing the
constraints directly declared on the given element. In case of BeanDescriptor
, the bean’s class-
level constraints are returned. More details on ConstraintDescriptor
can be found in
ConstraintDescriptor
.
Via getConstraintsForProperty()
, getConstraintsForMethod()
and getConstraintsForConstructor()
you
can obtain a descriptor representing one given property or executable element, identified by its
name and, in case of methods and constructors, parameter types. The different descriptor types
returned by these methods are described in the following sections.
Note that these methods consider constraints declared at super-types according to the rules for
constraint inheritance as described in Constraint inheritance. An example is the
descriptor for the manufacturer
property, which provides access to all constraints defined on
Vehicle#getManufacturer()
and the implementing method Car#getManufacturer()
. null
is returned in
case the specified element does not exist or is not constrained.
The methods getConstrainedProperties()
, getConstrainedMethods()
and getConstrainedConstructors()
return (potentially empty) sets with all constrained properties, methods and constructors,
respectively. An element is considered constrained, if it has at least one constraint or is marked
for cascaded validation. When invoking getConstrainedMethods()
, you can specify the type of the
methods to be returned (getters, non-getters or both).
9.2. PropertyDescriptor
The interface
PropertyDescriptor
represents one given property of a
class. It is transparent whether constraints are declared on a field or a property getter, provided
the JavaBeans naming conventions are respected. Using PropertyDescriptor
shows
how to use the PropertyDescriptor
interface.
PropertyDescriptor
PropertyDescriptor licensePlateDescriptor = carDescriptor.getConstraintsForProperty(
"licensePlate"
);
//"licensePlate" has two constraints, is not marked with @Valid and defines no group conversions
assertEquals( "licensePlate", licensePlateDescriptor.getPropertyName() );
assertEquals( 2, licensePlateDescriptor.getConstraintDescriptors().size() );
assertTrue( licensePlateDescriptor.hasConstraints() );
assertFalse( licensePlateDescriptor.isCascaded() );
assertTrue( licensePlateDescriptor.getGroupConversions().isEmpty() );
PropertyDescriptor driverDescriptor = carDescriptor.getConstraintsForProperty( "driver" );
//"driver" has no constraints, is marked with @Valid and defines one group conversion
assertEquals( "driver", driverDescriptor.getPropertyName() );
assertTrue( driverDescriptor.getConstraintDescriptors().isEmpty() );
assertFalse( driverDescriptor.hasConstraints() );
assertTrue( driverDescriptor.isCascaded() );
assertEquals( 1, driverDescriptor.getGroupConversions().size() );
Using getConstrainedDescriptors()
, you can retrieve a set of ConstraintDescriptors
providing more
information on the individual constraints of a given property. The method isCascaded()
returns
true
, if the property is marked for cascaded validation (either using the @Valid
annotation or via
XML), false
otherwise. Any configured group conversions are returned by getGroupConversions()
. See
GroupConversionDescriptor
for more details on GroupConversionDescriptor
.
9.3. MethodDescriptor
and ConstructorDescriptor
Constrained methods and constructors are represented by the interfaces
MethodDescriptor
and ConstructorDescriptor
, respectively.
Using MethodDescriptor
and ConstructorDescriptor
demonstrates how to work with these
descriptors.
MethodDescriptor
and ConstructorDescriptor
//driveAway(int) has a constrained parameter and an unconstrained return value
MethodDescriptor driveAwayDescriptor = carDescriptor.getConstraintsForMethod(
"driveAway",
int.class
);
assertEquals( "driveAway", driveAwayDescriptor.getName() );
assertTrue( driveAwayDescriptor.hasConstrainedParameters() );
assertFalse( driveAwayDescriptor.hasConstrainedReturnValue() );
//always returns an empty set; constraints are retrievable by navigating to
//one of the sub-descriptors, e.g. for the return value
assertTrue( driveAwayDescriptor.getConstraintDescriptors().isEmpty() );
ParameterDescriptor speedDescriptor = driveAwayDescriptor.getParameterDescriptors()
.get( 0 );
//The "speed" parameter is located at index 0, has one constraint and is not cascaded
//nor does it define group conversions
assertEquals( "arg0", speedDescriptor.getName() );
assertEquals( 0, speedDescriptor.getIndex() );
assertEquals( 1, speedDescriptor.getConstraintDescriptors().size() );
assertFalse( speedDescriptor.isCascaded() );
assert speedDescriptor.getGroupConversions().isEmpty();
//getDriver() has no constrained parameters but its return value is marked for cascaded
//validation and declares one group conversion
MethodDescriptor getDriverDescriptor = carDescriptor.getConstraintsForMethod(
"getDriver"
);
assertFalse( getDriverDescriptor.hasConstrainedParameters() );
assertTrue( getDriverDescriptor.hasConstrainedReturnValue() );
ReturnValueDescriptor returnValueDescriptor = getDriverDescriptor.getReturnValueDescriptor();
assertTrue( returnValueDescriptor.getConstraintDescriptors().isEmpty() );
assertTrue( returnValueDescriptor.isCascaded() );
assertEquals( 1, returnValueDescriptor.getGroupConversions().size() );
//load(List<Person>, List<PieceOfLuggage>) has one cross-parameter constraint
MethodDescriptor loadDescriptor = carDescriptor.getConstraintsForMethod(
"load",
List.class,
List.class
);
assertTrue( loadDescriptor.hasConstrainedParameters() );
assertFalse( loadDescriptor.hasConstrainedReturnValue() );
assertEquals(
1,
loadDescriptor.getCrossParameterDescriptor().getConstraintDescriptors().size()
);
//Car(String, String, Person, String) has one constrained parameter
ConstructorDescriptor constructorDescriptor = carDescriptor.getConstraintsForConstructor(
String.class,
String.class,
Person.class,
String.class
);
assertEquals( "Car", constructorDescriptor.getName() );
assertFalse( constructorDescriptor.hasConstrainedReturnValue() );
assertTrue( constructorDescriptor.hasConstrainedParameters() );
assertEquals(
1,
constructorDescriptor.getParameterDescriptors()
.get( 0 )
.getConstraintDescriptors()
.size()
);
getName()
returns the name of the given method or constructor. The methods
hasConstrainedParameters()
and hasConstrainedReturnValue()
can be used to perform a quick check
whether an executable element has any parameter constraints (either constraints on single parameters
or cross-parameter constraints) or return value constraints.
Note that any constraints are not directly exposed on MethodDescriptor
and ConstructorDescriptor
,
but rather on dedicated descriptors representing an executable’s parameters, its return value and
its cross-parameter constraints. To get hold of one of these descriptors, invoke
getParameterDescriptors()
, getReturnValueDescriptor()
or getCrossParameterDescriptor()
,
respectively.
These descriptors provide access to the element’s constraints (getConstraintDescriptors()
) and, in
case of parameters and return value, to its configuration for cascaded validation (isValid()
and
getGroupConversions()
). For parameters, you also can retrieve the index and the name, as returned by
the currently used parameter name provider (see ParameterNameProvider
) via getName()
and getIndex()
.
Getter methods following the JavaBeans naming conventions are considered as bean properties but also as constrained methods. That means you can retrieve the related metadata either by obtaining a |
9.4. ElementDescriptor
The ElementDiscriptor
interface is the common base class for the
individual descriptor types such as BeanDescriptor
, PropertyDescriptor
etc. Besides
getConstraintDescriptors()
it provides some more methods common to all descriptors.
hasConstraints()
allows for a quick check whether an element has any direct constraints (e.g. class-
level constraints in case of BeanDescriptor
). getElementClass()
returns the Java type of the element
represented by a given descriptor. More specifically, the method returns
-
the object type when invoked on
BeanDescriptor
, -
the type of a property or parameter when invoked on
PropertyDescriptor
orParameterDescriptor
respectively, -
Object[].class
when invoked onCrossParameterDescriptor
, -
the return type when invoked on
ConstructorDescriptor
,MethodDescriptor
orReturnValueDescriptor
.void.class
will be returned for methods which don’t have a return value.
Using ElementDescriptor methods
shows how these methods are used.
ElementDescriptor methods
PropertyDescriptor manufacturerDescriptor = carDescriptor.getConstraintsForProperty(
"manufacturer"
);
assertTrue( manufacturerDescriptor.hasConstraints() );
assertEquals( String.class, manufacturerDescriptor.getElementClass() );
CrossParameterDescriptor loadCrossParameterDescriptor = carDescriptor.getConstraintsForMethod(
"load",
List.class,
List.class
).getCrossParameterDescriptor();
assertTrue( loadCrossParameterDescriptor.hasConstraints() );
assertEquals( Object[].class, loadCrossParameterDescriptor.getElementClass() );
Finally, ElementDescriptor
offers access to the ConstraintFinder
API which allows you to query for
constraint metadata in a fine grained way. Usage of ConstraintFinder
shows how to retrieve a
ConstraintFinder
instance via findConstraints()
and use the API to query for constraint metadata.
ConstraintFinder
PropertyDescriptor manufacturerDescriptor = carDescriptor.getConstraintsForProperty(
"manufacturer"
);
//"manufacturer" constraints are declared on the getter, not the field
assertTrue(
manufacturerDescriptor.findConstraints()
.declaredOn( ElementType.FIELD )
.getConstraintDescriptors()
.isEmpty()
);
//@NotNull on Vehicle#getManufacturer() is part of another group
assertEquals(
1,
manufacturerDescriptor.findConstraints()
.unorderedAndMatchingGroups( Default.class )
.getConstraintDescriptors()
.size()
);
//@Size on Car#getManufacturer()
assertEquals(
1,
manufacturerDescriptor.findConstraints()
.lookingAt( Scope.LOCAL_ELEMENT )
.getConstraintDescriptors()
.size()
);
//@Size on Car#getManufacturer() and @NotNull on Vehicle#getManufacturer()
assertEquals(
2,
manufacturerDescriptor.findConstraints()
.lookingAt( Scope.HIERARCHY )
.getConstraintDescriptors()
.size()
);
//Combining several filter options
assertEquals(
1,
manufacturerDescriptor.findConstraints()
.declaredOn( ElementType.METHOD )
.lookingAt( Scope.HIERARCHY )
.unorderedAndMatchingGroups( Vehicle.Basic.class )
.getConstraintDescriptors()
.size()
);
Via declaredOn()
you can search for ConstraintDescriptors
declared on certain element types. This is
useful to find property constraints declared on either fields or getter methods.
unorderedAndMatchingGroups()
restricts the resulting constraints to those matching the given
validation group(s).
lookingAt()
allows to distinguish between constraints directly specified on the element
(Scope.LOCAL_ELEMENT
) or constraints belonging to the element but hosted anywhere in the class
hierarchy (Scope.HIERARCHY
).
You can also combine the different options as shown in the last example.
Order is not respected by |
9.5. GroupConversionDescriptor
All those descriptor types that represent elements which can be subject of cascaded validation
(i.e., PropertyDescriptor
, ParameterDescriptor
and ReturnValueDescriptor
) provide access to the
element’s group conversions via getGroupConversions()
. The returned set contains a
GroupConversionDescriptor
for each configured conversion, allowing to retrieve
source and target groups of the conversion. Using GroupConversionDescriptor
shows an example.
GroupConversionDescriptor
PropertyDescriptor driverDescriptor = carDescriptor.getConstraintsForProperty( "driver" );
Set<GroupConversionDescriptor> groupConversions = driverDescriptor.getGroupConversions();
assertEquals( 1, groupConversions.size() );
GroupConversionDescriptor groupConversionDescriptor = groupConversions.iterator()
.next();
assertEquals( Default.class, groupConversionDescriptor.getFrom() );
assertEquals( Person.Basic.class, groupConversionDescriptor.getTo() );
9.6. ConstraintDescriptor
Last but not least, the
ConstraintDescriptor
interface describes a
single constraint together with its composing constraints. Via an instance of this interface you get
access to the constraint annotation and its parameters.
Using ConstraintDescriptor
shows how to retrieve default constraint attributes (such as message template, groups etc.) as well
as custom constraint attributes (piecesOfLuggagePerPassenger
) and other metadata such as the
constraint’s annotation type and its validators from a ConstraintDescriptor
.
ConstraintDescriptor
//descriptor for the @LuggageCountMatchesPassengerCount constraint on the
//load(List<Person>, List<PieceOfLuggage>) method
ConstraintDescriptor<?> constraintDescriptor = carDescriptor.getConstraintsForMethod(
"load",
List.class,
List.class
).getCrossParameterDescriptor().getConstraintDescriptors().iterator().next();
//constraint type
assertEquals(
LuggageCountMatchesPassengerCount.class,
constraintDescriptor.getAnnotation().annotationType()
);
//standard constraint attributes
assertEquals( SeverityInfo.class, constraintDescriptor.getPayload().iterator().next() );
assertEquals(
ConstraintTarget.PARAMETERS,
constraintDescriptor.getValidationAppliesTo()
);
assertEquals( Default.class, constraintDescriptor.getGroups().iterator().next() );
assertEquals(
"There must not be more than {piecesOfLuggagePerPassenger} pieces of luggage per " +
"passenger.",
constraintDescriptor.getMessageTemplate()
);
//custom constraint attribute
assertEquals(
2,
constraintDescriptor.getAttributes().get( "piecesOfLuggagePerPassenger" )
);
//no composing constraints
assertTrue( constraintDescriptor.getComposingConstraints().isEmpty() );
//validator class
assertEquals(
Arrays.<Class<?>>asList( LuggageCountMatchesPassengerCount.Validator.class ),
constraintDescriptor.getConstraintValidatorClasses()
);
10. Integrating with other frameworks
Hibernate Validator is intended to be used to implement multi-layered data validation, where constraints are expressed in a single place (the annotated domain model) and checked in various different layers of the application. For this reason there are multiple integration points with other technologies.
10.1. ORM integration
Hibernate Validator integrates with both Hibernate and all pure Java Persistence providers.
When lazy loaded associations are supposed to be validated it is recommended to place the constraint on the getter of the association. Hibernate replaces lazy loaded associations with proxy instances which get initialized/loaded when requested via the getter. If, in such a case, the constraint is placed on field level the actual proxy instance is used which will lead to validation errors. |
10.1.1. Database schema-level validation
Out of the box, Hibernate (as of version 3.5.x) will translate the constraints you have defined for
your entities into mapping metadata. For example, if a property of your entity is annotated
@NotNull
, its columns will be declared as not null
in the DDL schema generated by Hibernate.
If, for some reason, the feature needs to be disabled, set hibernate.validator.apply_to_ddl
to
false
. See also Bean Validation constraints and Additional constraints.
You can also limit the DDL constraint generation to a subset of the defined constraints by setting
the property org.hibernate.validator.group.ddl
. The property specifies the comma-separated, fully
specified class names of the groups a constraint has to be part of in order to be considered for DDL
schema generation.
10.1.2. Hibernate event-based validation
Hibernate Validator has a built-in Hibernate event listener -
org.hibernate.cfg.beanvalidation.BeanValidationEventListener
-
which is part of Hibernate ORM. Whenever a PreInsertEvent
,
PreUpdateEvent
or PreDeleteEvent
occurs, the listener will verify all constraints of the entity
instance and throw an exception if any constraint is violated. Per default objects will be checked
before any inserts or updates are made by Hibernate. Pre deletion events will per default not
trigger a validation. You can configure the groups to be validated per event type using the
properties javax.persistence.validation.group.pre-persist
,
javax.persistence.validation.group.pre-update
and javax.persistence.validation.group.pre-remove
.
The values of these properties are the comma-separated, fully specified class names of the groups
to validate. Manual configuration of BeanValidationEvenListener
shows the default values for these
properties. In this case they could also be omitted.
On constraint violation, the event will raise a runtime ConstraintViolationException
which contains
a set of ConstraintViolation
instances describing each failure.
If Hibernate Validator is present in the classpath, Hibernate ORM will use it transparently.
To avoid validation even though Hibernate Validator is in the classpath set
javax.persistence.validation.mode
to none.
If the beans are not annotated with validation annotations, there is no runtime performance cost. |
In case you need to manually set the event listeners for Hibernate ORM, use the following configuration in hibernate.cfg.xml:
BeanValidationEvenListener
<hibernate-configuration>
<session-factory>
...
<property name="javax.persistence.validation.group.pre-persist">
javax.validation.groups.Default
</property>
<property name="javax.persistence.validation.group.pre-update">
javax.validation.groups.Default
</property>
<property name="javax.persistence.validation.group.pre-remove"></property>
...
<event type="pre-update">
<listener class="org.hibernate.cfg.beanvalidation.BeanValidationEventListener"/>
</event>
<event type="pre-insert">
<listener class="org.hibernate.cfg.beanvalidation.BeanValidationEventListener"/>
</event>
<event type="pre-delete">
<listener class="org.hibernate.cfg.beanvalidation.BeanValidationEventListener"/>
</event>
</session-factory>
</hibernate-configuration>
10.1.3. JPA
If you are using JPA 2 and Hibernate Validator is in the classpath the JPA2 specification requires
that Bean Validation gets enabled. The properties javax.persistence.validation.group.pre-persist
,
javax.persistence.validation.group.pre-update
and javax.persistence.validation.group.pre-remove
as
described in Hibernate event-based validation can in this case be configured in
persistence.xml. persistence.xml also defines a node validation-mode which can be set to AUTO
,
CALLBACK
, NONE
. The default is AUTO
.
In a JPA 1 you will have to create and register Hibernate Validator yourself. In case you are using
Hibernate EntityManager you can add a customized version of the BeanValidationEventListener
described in Hibernate event-based validation to your project and register it
manually.
10.2. JSF & Seam
When working with JSF2 or JBoss Seam and Hibernate Validator (Bean Validation) is present in the
runtime environment, validation is triggered for every field in the application. Usage of Bean Validation within JSF2
shows an example of the f:validateBean
tag in a JSF page. The validationGroups
attribute is optional
and can be used to specify a comma separated list of validation groups. The default is
javax.validation.groups.Default
. For more information refer to the Seam documentation or the JSF 2
specification.
<h:form>
<f:validateBean validationGroups="javax.validation.groups.Default">
<h:inputText value=#{model.property}/>
<h:selectOneRadio value=#{model.radioProperty}> ... </h:selectOneRadio>
<!-- other input components here -->
</f:validateBean>
</h:form>
The integration between JSF 2 and Bean Validation is described in the "Bean Validation Integration"
chapter of JSR-314. It is interesting to know that JSF
2 implements a custom javax.faces.validator.BeanValidator.MESSAGE={1}: {0} The default is: javax.faces.validator.BeanValidator.MESSAGE={0} |
10.3. CDI
As of version 1.1, Bean Validation is integrated with CDI (Contexts and Dependency Injection for JavaTM EE).
This integration provides CDI managed beans for Validator
and ValidatorFactory
and enables
dependency injection in constraint validators as well as custom message interpolators, traversable
resolvers, constraint validator factories and parameter name providers.
Furthermore, parameter and return value constraints on the methods and constructors of CDI managed beans will automatically be validated upon invocation.
When your application runs on a Java EE container, this integration is enabled by default. When working with CDI in a Servlet container or in a pure Java SE environment, you can use the CDI portable extension provided by Hibernate Validator. To do so, add the portable extension to your class path as described in CDI.
10.3.1. Dependency injection
CDI’s dependency injection mechanism makes it very easy to retrieve ValidatorFactory
and Validator
instances and use them in your managed beans. Just annotate instance fields of your bean with
@javax.inject.Inject
as shown in Retrieving validator factory and validator via @Inject
.
@Inject
package org.hibernate.validator.referenceguide.chapter10.cdi.validator;
@ApplicationScoped
public class RentalStation {
@Inject
private ValidatorFactory validatorFactory;
@Inject
private Validator validator;
//...
}
The injected beans are the default validator factory and validator instances. In order to configure them - e.g. to use a custom message interpolator - you can use the Bean Validation XML descriptors as discussed in Configuring via XML.
If you are working with several Bean Validation providers you can make sure that factory and
validator from Hibernate Validator are injected by annotating the injection points with the
@HibernateValidator
qualifier which is demonstrated in Using the @HibernateValidator
qualifier annotation.
@HibernateValidator
qualifier annotationpackage org.hibernate.validator.referenceguide.chapter10.cdi.validator.qualifier;
@ApplicationScoped
public class RentalStation {
@Inject
@HibernateValidator
private ValidatorFactory validatorFactory;
@Inject
@HibernateValidator
private Validator validator;
//...
}
The fully-qualified name of the qualifier annotation is
|
Via @Inject
you also can inject dependencies into constraint validators and other Bean Validation
objects such as MessageInterpolator
implementations etc.
Constraint validator with injected bean
demonstrates how an injected CDI bean is used in a ConstraintValidator
implementation to determine
whether the given constraint is valid or not. As the example shows, you also can work with the
@PostConstruct
and @PreDestroy
callbacks to implement any required construction and destruction
logic.
package org.hibernate.validator.referenceguide.chapter10.cdi.injection;
public class ValidLicensePlateValidator
implements ConstraintValidator<ValidLicensePlate, String> {
@Inject
private VehicleRegistry vehicleRegistry;
@PostConstruct
public void postConstruct() {
//do initialization logic...
}
@PreDestroy
public void preDestroy() {
//do destruction logic...
}
@Override
public void initialize(ValidLicensePlate constraintAnnotation) {
}
@Override
public boolean isValid(String licensePlate, ConstraintValidatorContext constraintContext) {
return vehicleRegistry.isValidLicensePlate( licensePlate );
}
}
10.3.2. Method validation
The method interception facilities of CDI allow for a very tight integration with Bean Validation’s method validation functionality. Just put constraint annotations to the parameters and return values of the executables of your CDI beans and they will be validated automatically before (parameter constraints) and after (return value constraints) a method or constructor is invoked.
Note that no explicit interceptor binding is required, instead the required method validation interceptor will automatically be registered for all managed beans with constrained methods and constructors.
The interceptor |
You can see an example in CDI managed beans with method-level constraints.
package org.hibernate.validator.referenceguide.chapter10.cdi.methodvalidation;
@ApplicationScoped
public class RentalStation {
@Valid
public RentalStation() {
//...
}
@NotNull
@Valid
public Car rentCar(
@NotNull Customer customer,
@NotNull @Future Date startDate,
@Min(1) int durationInDays) {
//...
return null;
}
@NotNull
List<Car> getAvailableCars() {
//...
return null;
}
}
package org.hibernate.validator.referenceguide.chapter10.cdi.methodvalidation;
@RequestScoped
public class RentCarRequest {
@Inject
private RentalStation rentalStation;
public void rentCar(String customerId, Date startDate, int duration) {
//causes ConstraintViolationException
rentalStation.rentCar( null, null, -1 );
}
}
Here the RentalStation
bean hosts several method constraints. When invoking one of the RentalStation
methods from another bean such as RentCarRequest
, the constraints of the invoked method are
automatically validated. If any illegal parameter values are passed as in the example, a
ConstraintViolationException
will be thrown by the method interceptor, providing detailed
information on the violated constraints. The same is the case if the method’s return value violates
any return value constraints.
Similarly, constructor constraints are validated automatically upon invocation. In the example the
RentalStation
object returned by the constructor will be validated since the constructor return
value is marked with @Valid
.
Validated executable types
Bean Validation allows for a fine-grained control of the executable types which are automatically
validated. By default, constraints on constructors and non-getter methods are validated. Therefore
the @NotNull
constraint on the method RentalStation#getAvailableCars()
in
CDI managed beans with method-level constraints gets not validated when the method is invoked.
You have the following options to configure which types of executables are validated upon invocation:
-
Configure the executable types globally via the XML descriptor META-INF/validation.xml; see Configuring the validator factory in validation.xml for an example
-
Use the
@ValidateOnExecution
annotation on the executable or type level
If several sources of configuration are specified for a given executable, @ValidateOnExecution
on
the executable level takes precedence over @ValidateOnExecution
on the type level and
@ValidateOnExecution
generally takes precedence over the globally configured types in META-
INF/validation.xml.
Using @ValidateOnExecution
shows how to use the @ValidateOnExecution
annotation:
@ValidateOnExecution
package org.hibernate.validator.referenceguide.chapter10.cdi.methodvalidation.configuration;
@ApplicationScoped
@ValidateOnExecution(type = ExecutableType.ALL)
public class RentalStation {
@Valid
public RentalStation() {
//...
}
@NotNull
@Valid
@ValidateOnExecution(type = ExecutableType.NONE)
public Car rentCar(
@NotNull Customer customer,
@NotNull @Future Date startDate,
@Min(1) int durationInDays) {
//...
return null;
}
@NotNull
public List<Car> getAvailableCars() {
//...
return null;
}
}
Here the method rentCar()
won’t be validated upon invocation because it is annotated with
@ValidateOnExecution(type = ExecutableType.NONE)
. In contrast, the constructor and the
method getAvailableCars()
will be validated due to @ValidateOnExecution(type =
ExecutableType.ALL)
being given on the type level. ExecutableType.ALL
is a more compact form for
explicitly specifying all the types CONSTRUCTORS
, GETTER_METHODS
and NON_GETTER_METHODS
.
Executable validation can be turned off globally by specifying
|
Note that when a method overrides or implements a super-type method the configuration will be taken
from that overridden or implemented method (as given via @ValidateOnExecution
on the method itself
or on the super-type). This protects a client of the super-type method from an unexpected alteration
of the configuration, e.g. disabling validation of an overridden executable in a sub-type.
In case a CDI managed bean overrides or implements a super-type method and this super-type method
hosts any constraints, it can happen that the validation interceptor is not properly registered with
the bean, resulting in the bean’s methods not being validated upon invocation. In this case you can
specify the executable type IMPLICIT
on the sub-class as shown in
Using ExecutableType.IMPLICIT
, which makes sure that all required metadata is discovered
an the validation interceptor kicks in when the methods on ExpressRentalStation
are invoked.
ExecutableType.IMPLICIT
package org.hibernate.validator.referenceguide.chapter10.cdi.methodvalidation.implicit;
@ValidateOnExecution(type = ExecutableType.ALL)
public interface RentalStation {
@NotNull
@Valid
Car rentCar(
@NotNull Customer customer,
@NotNull @Future Date startDate,
@Min(1) int durationInDays);
@NotNull
List<Car> getAvailableCars();
}
package org.hibernate.validator.referenceguide.chapter10.cdi.methodvalidation.implicit;
@ApplicationScoped
@ValidateOnExecution(type = ExecutableType.IMPLICIT)
public class ExpressRentalStation implements RentalStation {
@Override
public Car rentCar(Customer customer, Date startDate, @Min(1) int durationInDays) {
//...
return null;
}
@Override
public List<Car> getAvailableCars() {
//...
return null;
}
}
10.4. Java EE
When your application runs on a Java EE application server such as http://wildfly.org/,
you also can obtain Validator
and ValidatorFactory
instances via @Resource
injection in
managed objects such as EJBs etc., as shown in Retrieving Validator
and ValidatorFactory
via @Resource
injection.
Validator
and ValidatorFactory
via @Resource
injectionpackage org.hibernate.validator.referenceguide.chapter10.javaee;
public class RentalStationBean {
@Resource
private ValidatorFactory validatorFactory;
@Resource
private Validator validator;
//...
}
Alternatively you can obtain a validator and a validator factory from JNDI under the names "java:comp/Validator" and "java:comp/ValidatorFactory", respectively.
Similar to CDI-based injection via @Inject
, these objects represent default validator and validator
factory and thus can be configured using the XML descriptor META-INF/validation.xml (see
Configuring via XML).
When your application is CDI-enabled, the injected objects are CDI-aware as well and e.g. support dependency injection in constraint validators.
10.5. JavaFX
Hibernate Validator also provides support for the unwrapping of JavaFX properties. If JavaFX is present
on the classpath a ValidatedValueUnwrapper
for JavaFX properties is automatically registered. In some
cases, however, it is also necessary to explicitly use @UnwrapValidatedValue
. This is required if
the constraint validator resolution is not unique and there is a potential constraint validator for
the actual JavaFX property as well as the contained property value itself.
See JavaFX unwrapper for examples and further discussion.
11. Hibernate Validator Specifics
In this chapter you will learn how to make use of several features provided by Hibernate Validator in addition to the functionality defined by the Bean Validation specification. This includes the fail fast mode, the API for programmatic constraint configuration and the boolean composition of constraints.
Using the features described in the following sections may result in application code which is not portable between Bean Validation providers. |
11.1. Public API
Let’s start, however, with a look at the public API of Hibernate Validator. Below you can find a list of all packages belonging to this API and their purpose. Note that when a package is part of the public API this is not necessarily true for its sub-packages.
org.hibernate.validator
-
Classes used by the Bean Validation bootstrap mechanism (eg. validation provider, configuration class); for more details see Bootstrapping.
org.hibernate.validator.cfg
,org.hibernate.validator.cfg.context
,org.hibernate.validator.cfg.defs
,org.hibernate.validator.spi.cfg
-
Hibernate Validator’s fluent API for constraint declaration; in
org.hibernate.validator.cfg
you will find theConstraintMapping
interface, inorg.hibernate.validator.cfg.defs
all constraint definitions and inorg.hibernate.validator.spi.cfg
a callback for using the API for configuring the default validator factory. Refer to Programmatic constraint definition and declaration for the details. org.hibernate.validator.constraints
,org.hibernate.validator.constraints.br
,org.hibernate.validator.constraints.pl
-
Some useful custom constraints provided by Hibernate Validator in addition to the built-in constraints defined by the Bean Validation specification; the constraints are described in detail in Additional constraints.
org.hibernate.validator.constraintvalidation
-
Extended constraint validator context which allows to set custom attributes for message interpolation.
HibernateConstraintValidatorContext
describes how to make use of that feature. org.hibernate.validator.group
,org.hibernate.validator.spi.group
-
The group sequence provider feature which allows you to define dynamic default group sequences in function of the validated object state; the specifics can be found in Redefining the default group sequence.
org.hibernate.validator.messageinterpolation
,org.hibernate.validator.resourceloading
,org.hibernate.validator.spi.resourceloading
-
Classes related to constraint message interpolation; the first package contains Hibernate Validator’s default message interpolator,
ResourceBundleMessageInterpolator
. The latter two packages provide theResourceBundleLocator
SPI for the loading of resource bundles (seeResourceBundleLocator
) and its default implementation. org.hibernate.validator.parameternameprovider
-
A
ParameterNameProvider
based on the ParaNamer library, see ParaNamer basedParameterNameProvider
. org.hibernate.validator.propertypath
-
Extensions to the
javax.validation.Path
API, see Extensions of the Path API. org.hibernate.validator.spi.constraintdefinition
-
An SPI for registering additional constraint validators programmatically, see Providing constraint definitions.
org.hibernate.validator.spi.time
-
An SPI for customizing the retrieval of the current time when validating
@Future
and@Past
, see Time providers for @Future and @Past. org.hibernate.validator.valuehandling
,org.hibernate.validator.spi.valuehandling
-
Classes related to the processing of values prior to thei validation, see Unwrapping values.
The public packages of Hibernate Validator fall into two categories: while the actual API parts are
intended to be invoked or used by clients (e.g. the API for programmatic constraint declaration
or the custom constraints), the SPI (service provider interface) packages contain interfaces which
are intended to be implemented by clients (e.g. |
Any packages not listed in that table are internal packages of Hibernate Validator and are not intended to be accessed by clients. The contents of these internal packages can change from release to release without notice, thus possibly breaking any client code relying on it.
11.2. Fail fast mode
Using the fail fast mode, Hibernate Validator allows to return from the current validation as soon as the first constraint violation occurs. This can be useful for the validation of large object graphs where you are only interested in a quick check whether there is any constraint violation at all.
Using the fail fast validation mode shows how to bootstrap and use a fail fast enabled validator.
package org.hibernate.validator.referenceguide.chapter11.failfast;
public class Car {
@NotNull
private String manufacturer;
@AssertTrue
private boolean isRegistered;
public Car(String manufacturer, boolean isRegistered) {
this.manufacturer = manufacturer;
this.isRegistered = isRegistered;
}
//getters and setters...
}
Validator validator = Validation.byProvider( HibernateValidator.class )
.configure()
.failFast( true )
.buildValidatorFactory()
.getValidator();
Car car = new Car( null, false );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
Here the validated object actually fails to satisfy both the constraints declared on the Car
class,
yet the validation call yields only one ConstraintViolation
since the fail fast mode is enabled.
There is no guarantee in which order the constraints are evaluated, i.e. it is not deterministic
whether the returned violation originates from the |
Refer to Provider-specific settings to learn about the different ways of enabling the fail fast mode when bootstrapping a validator.
11.3. Relaxation of requirements for method validation in class hierarchies
The Bean Validation specification defines a set of preconditions which apply when defining constraints on methods within class hierarchies. These preconditions are defined in section 4.5.5 of the Bean Validation 1.1 specification. See also Method constraints in inheritance hierarchies in this guide.
As per specification a Bean Validation provider is allowed to relax these preconditions. With Hibernate Validator you can do this in one of two ways.
First you can use the configuration properties hibernate.validator.allow_parameter_constraint_override, hibernate.validator.allow_multiple_cascaded_validation_on_result and hibernate.validator.allow_parallel_method_parameter_constraint in validation.xml. See example Configuring method validation behaviour in class hierarchies via properties.
<?xml version="1.0" encoding="UTF-8"?>
<validation-config
xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration validation-configuration-1.0.xsd">
<default-provider>org.hibernate.validator.HibernateValidator</default-provider>
<property name="hibernate.validator.allow_parameter_constraint_override">true</property>
<property name="hibernate.validator.allow_multiple_cascaded_validation_on_result">true</property>
<property name="hibernate.validator.allow_parallel_method_parameter_constraint">true</property>
</validation-config>
Alternatively these settings can be applied during programmatic bootstrapping.
HibernateValidatorConfiguration configuration = Validation.byProvider( HibernateValidator.class ).configure();
configuration.allowMultipleCascadedValidationOnReturnValues( true )
.allowOverridingMethodAlterParameterConstraint( true )
.allowParallelMethodsDefineParameterConstraints( true );
By default, all of these properties are false, implementing the default behavior as defined in the Bean Validation specification.
Changing the default behaviour for method validation will result in non specification conform and non portable application. Make sure to understand what you are doing and that your use case really requires changes to the default behaviour. |
11.4. Programmatic constraint definition and declaration
As per the Bean Validation specification, you can define and declare constraints using Java annotations and XML based constraint mappings.
In addition, Hibernate Validator provides a fluent API which allows for the programmatic configuration of constraints. Use cases include the dynamic addition of constraints at runtime depending on some application state or tests where you need entities with different constraints in different scenarios but don’t want to implement actual Java classes for each test case.
By default, constraints added via the fluent API are additive to constraints configured via the standard configuration capabilities. But it is also possible to ignore annotation and XML configured constraints where required.
The API is centered around the ConstraintMapping
interface. You obtain a new mapping via
HibernateValidatorConfiguration#createConstraintMapping()
which you then can configure in a fluent
manner as shown in Programmatic constraint declaration.
HibernateValidatorConfiguration configuration = Validation
.byProvider( HibernateValidator.class )
.configure();
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.property( "manufacturer", FIELD )
.constraint( new NotNullDef() )
.property( "licensePlate", FIELD )
.ignoreAnnotations()
.constraint( new NotNullDef() )
.constraint( new SizeDef().min( 2 ).max( 14 ) )
.type( RentalCar.class )
.property( "rentalStation", METHOD )
.constraint( new NotNullDef() );
Validator validator = configuration.addMapping( constraintMapping )
.buildValidatorFactory()
.getValidator();
Constraints can be configured on multiple classes and properties using method chaining. The
constraint definition classes NotNullDef
and SizeDef are helper classes which allow to configure
constraint parameters in a type-safe fashion. Definition classes exist for all built-in constraints
in the org.hibernate.validator.cfg.defs
package. By calling ignoreAnnotations()
any constraints
configured via annotations or XML are ignored for the given element.
Each element (type, property, method etc.) may only be configured once within all the constraint
mappings used to set up one validator factory. Otherwise a |
It is not supported to add constraints to non-overridden supertype properties and methods by configuring a subtype. Instead you need to configure the supertype in this case. |
Having configured the mapping, you must add it back to the configuration object from which you then can obtain a validator factory.
For custom constraints you can either create your own definition classes extending ConstraintDef
or
you can use GenericConstraintDef
as seen in Programmatic declaration of a custom constraint.
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.property( "licensePlate", FIELD )
.constraint( new GenericConstraintDef<CheckCase>( CheckCase.class )
.param( "value", CaseMode.UPPER )
);
By invoking valid()
you can mark a member for cascaded validation which is equivalent to annotating
it with @Valid
. Configure any group conversions to be applied during cascaded validation using the
convertGroup()
method (equivalent to @ConvertGroup
). An example can be seen in
Marking a property for cascaded validation.
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.property( "driver", FIELD )
.constraint( new NotNullDef() )
.valid()
.convertGroup( Default.class ).to( PersonDefault.class )
.type( Person.class )
.property( "name", FIELD )
.constraint( new NotNullDef().groups( PersonDefault.class ) );
You can not only configure bean constraints using the fluent API but also method and constructor constraints. As shown in Programmatic declaration of method and constructor constraints constructors are identified by their parameter types and methods by their name and parameter types. Having selected a method or constructor, you can mark its parameters and/or return value for cascaded validation and add constraints as well as cross-parameter constraints.
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.constructor( String.class )
.parameter( 0 )
.constraint( new SizeDef().min( 3 ).max( 50 ) )
.returnValue()
.valid()
.method( "drive", int.class )
.parameter( 0 )
.constraint( new MaxDef().value( 75 ) )
.method( "load", List.class, List.class )
.crossParameter()
.constraint( new GenericConstraintDef<LuggageCountMatchesPassengerCount>(
LuggageCountMatchesPassengerCount.class ).param(
"piecesOfLuggagePerPassenger", 2
)
)
.method( "getDriver" )
.returnValue()
.constraint( new NotNullDef() )
.valid();
Last but not least you can configure the default group sequence or the default group sequence provider of a type as shown in the following example.
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.defaultGroupSequence( Car.class, CarChecks.class )
.type( RentalCar.class )
.defaultGroupSequenceProviderClass( RentalCarGroupSequenceProvider.class );
11.5. Applying programmatic constraint declarations to the default validator factory
If you are not bootstrapping a validator factory manually
but work with the default factory as configured via META-INF/validation.xml
(see Configuring via XML),
you can add one or more constraint mappings by creating one or several constraint mapping contributors.
To do so, implement the ConstraintMappingContributor
contract:
ConstraintMappingContributor
implementationpackage org.hibernate.validator.referenceguide.chapter11.constraintapi;
public class MyConstraintMappingContributor implements ConstraintMappingContributor {
@Override
public void createConstraintMappings(ConstraintMappingBuilder builder) {
builder.addConstraintMapping()
.type( Marathon.class )
.property( "name", METHOD )
.constraint( new NotNullDef() )
.property( "numberOfHelpers", FIELD )
.constraint( new MinDef().value( 1 ) );
builder.addConstraintMapping()
.type( Runner.class )
.property( "paidEntryFee", FIELD )
.constraint( new AssertTrueDef() );
}
}
You then need to specify the fully-qualified class name of the contributor implementation in META-INF/validation.xml,
using the property key hibernate.validator.constraint_mapping_contributors
. You can specify several
contributors by separating them with a comma.
11.6. Advanced constraint composition features
11.6.1. Validation target specification for purely composed constraints
In case you specify a purely composed constraint - i.e. a constraint which has no validator itself but is solely made up from other, composing constraints - on a method declaration, the validation engine cannot determine whether that constraint is to be applied as a return value constraint or as a cross-parameter constraint.
Hibernate Validator allows to resolve such ambiguities by specifying the @SupportedValidationTarget
annotation on the
declaration of the composed constraint type as shown in Specifying the validation target of a purely composed constraint.
The @ValidInvoiceAmount
does not declare any validator, but it is solely composed by the @Min
and @NotNull
constraints. The @SupportedValidationTarget
ensures that the constraint is applied to the method return value when
given on a method declaration.
package org.hibernate.validator.referenceguide.chapter11.purelycomposed;
@Min(value = 0)
@NotNull
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {})
@SupportedValidationTarget(ValidationTarget.ANNOTATED_ELEMENT)
@ReportAsSingleViolation
public @interface ValidInvoiceAmount {
String message() default "{org.hibernate.validator.referenceguide.chapter11.purelycomposed."
+ "ValidInvoiceAmount.message}";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
@OverridesAttribute(constraint = Min.class, name = "value")
long value();
}
11.6.2. Boolean composition of constraints
Bean Validation specifies that the constraints of a composed constraint (see Constraint composition) are all combined via a logical AND. This means all of the composing constraints need to return true in order for an overall successful validation.
Hibernate Validator offers an extension to this and allows you to compose constraints via a logical OR or NOT. To do so you have to use the ConstraintComposition annotation and the enum CompositionType with its values AND, OR and ALL_FALSE.
OR composition of constraints shows how to build a composed constraint @PatternOrSize
where only one of the composing constraints needs to be valid in order to pass the validation.
Either the validated string is all lower-cased or it is between two and three characters long.
package org.hibernate.validator.referenceguide.chapter11.booleancomposition;
@ConstraintComposition(OR)
@Pattern(regexp = "[a-z]")
@Size(min = 2, max = 3)
@ReportAsSingleViolation
@Target({ METHOD, FIELD })
@Retention(RUNTIME)
@Constraint(validatedBy = { })
public @interface PatternOrSize {
String message() default "{org.hibernate.validator.referenceguide.chapter11." +
"booleancomposition.PatternOrSize.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
Using ALL_FALSE as composition type implicitly enforces that only a single violation will get reported in case validation of the constraint composition fails. |
11.7. Extensions of the Path API
Hibernate Validator provides an extension to the javax.validation.Path
API.
For nodes of ElementKind.PROPERTY
it allows to obtain the value of the represented property.
To do so, narrow down a given node to the type org.hibernate.validator.path.PropertyNode
using Node#as()
, as shown in the following example:
Building building = new Building();
// Assume the name of the person violates a @Size constraint
Person bob = new Person( "Bob" );
Apartment bobsApartment = new Apartment( bob );
building.getApartments().add( bobsApartment );
Set<ConstraintViolation<Building>> constraintViolations = validator.validate( building );
Path path = constraintViolations.iterator().next().getPropertyPath();
Iterator<Path.Node> nodeIterator = path.iterator();
Path.Node node = nodeIterator.next();
assertEquals( node.getName(), "apartments" );
assertSame( node.as( PropertyNode.class ).getValue(), bobsApartment );
node = nodeIterator.next();
assertEquals( node.getName(), "resident" );
assertSame( node.as( PropertyNode.class ).getValue(), bob );
node = nodeIterator.next();
assertEquals( node.getName(), "name" );
assertEquals( node.as( PropertyNode.class ).getValue(), "Bob" );
This is specifically useful to obtain the element of Set
properties on the property path (e.g. apartments
in the example) which otherwise could not be identified (unlike for Map
and List
, there is no key nor index in this case).
11.8. Dynamic payload as part of ConstraintViolation
In some cases automatic processing of violations can be aided, if the constraint violation provides additional data - a so called dynamic payload. This dynamic payload could for example contain hints to the user on how to resolve the violation.
Dynamic payloads can be set in custom constraints using HibernateConstraintValidatorContext
.
This is shown in example ConstraintValidator implementation setting a dynamic payload where the
javax.validation.ConstraintValidatorContext
is unwrapped to HibernateConstraintValidatorContext
in order to call
withDynamicPayload
.
package org.hibernate.validator.referenceguide.chapter11.dynamicpayload;
import static org.hibernate.validator.internal.util.CollectionHelper.newHashMap;
public class ValidPassengerCountValidator implements ConstraintValidator<ValidPassengerCount, Car> {
private static final Map<Integer, String> suggestedCars = newHashMap();
static {
suggestedCars.put( 2, "Chevrolet Corvette" );
suggestedCars.put( 3, "Toyota Volta" );
suggestedCars.put( 4, "Maserati GranCabrio" );
suggestedCars.put( 5, " Mercedes-Benz E-Class" );
}
@Override
public void initialize(ValidPassengerCount constraintAnnotation) {
}
@Override
public boolean isValid(Car car, ConstraintValidatorContext context) {
if ( car == null ) {
return true;
}
int passengerCount = car.getPassengers().size();
if ( car.getSeatCount() >= passengerCount ) {
return true;
}
else {
if ( suggestedCars.containsKey( passengerCount ) ) {
HibernateConstraintValidatorContext hibernateContext = context.unwrap(
HibernateConstraintValidatorContext.class
);
hibernateContext.withDynamicPayload( suggestedCars.get( passengerCount ) );
}
return false;
}
}
}
On the constraint violation processing side, a javax.validation.ConstraintViolation
can then in turn be
unwrapped to HibernateConstraintViolation
in order to retrieve the dynamic payload for further processing.
Car car = new Car( 2 );
car.addPassenger( new Person() );
car.addPassenger( new Person() );
car.addPassenger( new Person() );
Set<ConstraintViolation<Car>> constraintViolations = validator.validate( car );
assertEquals( 1, constraintViolations.size() );
ConstraintViolation<Car> constraintViolation = constraintViolations.iterator().next();
@SuppressWarnings("unchecked")
HibernateConstraintViolation<Car> hibernateConstraintViolation = constraintViolation.unwrap(
HibernateConstraintViolation.class
);
String suggestedCar = hibernateConstraintViolation.getDynamicPayload( String.class );
assertEquals( "Toyota Volta", suggestedCar );
11.9. ParameterMessageInterpolator
Hibernate Validator requires per default an implementation of the Unified EL (see Unified EL) to be available. This is needed to allow the interpolation of constraint error messages using EL expressions as defined by Bean Validation 1.1.
For environments where you cannot or do not want to provide an EL implementation, Hibernate Validators
offers a non EL based message interpolator - org.hibernate.validator.messageinterpolation.ParameterMessageInterpolator
.
Refer to Custom message interpolation to see how to plug in custom message interpolator implementations.
Constraint messages containing EL expressions will be returned un-interpolated by
|
11.10. ResourceBundleLocator
With ResourceBundleLocator
, Hibernate Validator provides an additional SPI which allows to retrieve
error messages from other resource bundles than ValidationMessages while still using the actual
interpolation algorithm as defined by the specification. Refer to
ResourceBundleLocator
to learn how to make use of that SPI.
11.11. Custom contexts
The Bean Validation specification offers at several points in its API the possibility to unwrap a
given interface to a implementor specific subtype. In the case of constraint violation creation in
ConstraintValidator
implementations as well as message interpolation in MessageInterpolator
instances, there exist unwrap()
methods for the provided context instances -
ConstraintValidatorContext
respectively MessageInterpolatorContext
. Hibernate Validator provides
custom extensions for both of these interfaces.
11.11.1. HibernateConstraintValidatorContext
HibernateConstraintValidatorContext
is a subtype of ConstraintValidatorContext
which allows you to:
-
set arbitrary parameters for interpolation via the Expression Language message interpolation facility using
HibernateConstraintValidatorContext#addExpressionVariable(String, Object)
. For an example refer to Custom @Future validator with message parameters.Note that the parameters specified via
addExpressionVariable(String, Object)
are global and apply for all constraint violations created by thisisValid()
invocation. This includes the default constraint violation, but also all violations created by theConstraintViolationBuilder
. You can, however, update the parameters between invocations ofConstraintViolationBuilder#addConstraintViolation()
. -
obtain the
TimeProvider
for getting the current time when validating@Future
and@Past
constraints (see also Time providers for @Future and @Past).This is useful if you want to customize the message of the
@Future
constraint. By default the message is just "must be in the future". Custom @Future validator with message parameters shows how to include the current date in order to make the message more explicit.Example 121. Custom @Future validator with message parameterspackage org.hibernate.validator.referenceguide.chapter11.context; public class MyFutureValidator implements ConstraintValidator<Future, Date> { @Override public void initialize(Future constraintAnnotation) { } @Override public boolean isValid(Date value, ConstraintValidatorContext context) { if ( value == null ) { return true; } HibernateConstraintValidatorContext hibernateContext = context.unwrap( HibernateConstraintValidatorContext.class ); Date now = new Date( hibernateContext.getTimeProvider().getCurrentTime() ); if ( !value.after( now ) ) { hibernateContext.disableDefaultConstraintViolation(); hibernateContext.addExpressionVariable( "now", now ) .buildConstraintViolationWithTemplate( "Must be after ${now}" ) .addConstraintViolation(); return false; } return true; } }
This functionality is currently experimental and might change in future versions.
-
set an arbitrary dynamic payload - see Dynamic payload as part of ConstraintViolation
11.11.2. HibernateMessageInterpolatorContext
Hibernate Validator also offers a custom extension of MessageInterpolatorContext
, namely
HibernateMessageInterpolatorContext
(see HibernateMessageInterpolatorContext
). This
subtype was introduced to allow a better integration of Hibernate Validator into the Glassfish. The
root bean type was in this case needed to determine the right classloader for the message resource
bundle. If you have any other usecases, let us know.
HibernateMessageInterpolatorContext
* @author Guillaume Smet
* @since 5.0
*/
public interface HibernateMessageInterpolatorContext extends MessageInterpolator.Context {
/**
* Returns the currently validated root bean type.
*
* @return The currently validated root bean type.
11.12. ParaNamer based ParameterNameProvider
Hibernate Validator comes with a ParameterNameProvider
implementation which leverages the
ParaNamer library.
This library provides several ways for obtaining parameter names at runtime, e.g. based on debug
symbols created by the Java compiler, constants with the parameter names woven into the bytecode in
a post-compile step or annotations such as the @Named
annotation from JSR 330.
In order to use ParanamerParameterNameProvider
, either pass an instance when bootstrapping a
validator as shown in Using a custom ParameterNameProvider
or specify
org.hibernate.validator.parameternameprovider.ParanamerParameterNameProvider
as value for the
<parameter-name-provider>
element in the META-INF/validation.xml file.
When using this parameter name provider, you need to add the ParaNamer library to your classpath. It
is available in the Maven Central repository with the group id |
By default ParanamerParameterNameProvider
retrieves parameter names from constants added to the byte
code at build time (via DefaultParanamer
) and debug symbols (via BytecodeReadingParanamer
).
Alternatively you can specify a Paranamer
implementation of your choice when creating a
ParanamerParameterNameProvider
instance.
11.13. Unwrapping values
Sometimes it is required to unwrap values prior to validating them. For example, in
Applying a constraint to wrapped value of a JavaFX property a JavaFX property type
is used to define an element of a domain model. The @Size
constraint is meant to be applied to the
string value not the wrapping Property
instance.
@Size(min = 3)
private Property<String> name = new SimpleStringProperty( "Bob" );
The concept of value unwrapping is considered experimental at this time and may evolve into more general means of value handling in future releases. Please let us know about your use cases for such functionality. |
Bean properties in JavaFX are typically not of simple data types like String
or int
, but are
wrapped in Property
types which allows to make them observable, use them for data binding etc. When
applying a constraint such as @Size
to an element of type Property<String>
without further
preparation, an exception would be raised, indicating that no suitable validator for that constraint
and data type can be found. Thus the validated value must be unwrapped from the containing property
object before looking up a validator and invoking it.
For unwrapping to occur a ValidatedValueUnwrapper
needs to be registered for the type
requiring unwrapping. Example Implementing the ValidatedValueUnwrapper interface shows how this
schematically looks for a JavaFX PropertyValueUnwrapper
. You just need to extend the SPI class
ValidatedValueUnwrapper
and implement its abstract methods.
package org.hibernate.validator.referenceguide.chapter11.valuehandling;
public class PropertyValueUnwrapper extends ValidatedValueUnwrapper<Property<?>> {
@Override
public Object handleValidatedValue(Property<?> value) {
//...
return null;
}
@Override
public Type getValidatedValueType(Type valueType) {
//...
return null;
}
}
The ValidatedValueUnwrapper
needs also to be registered with the ValidatorFactory
:
Validator validator = Validation.byProvider( HibernateValidator.class )
.configure()
.addValidatedValueHandler( new PropertyValueUnwrapper() )
.buildValidatorFactory()
.getValidator();
Several unwrapper implementations can be registered. During constraint validator resolution
Hibernate Validator automatically checks whether a ValidatedValueUnwrapper
exists for the validated
value. If so, unwrapping occurs automatically. In some cases, however, constraint validator instances
for a given constraint might exist for the wrapper as well as the wrapped value (@NotNull
for example
applies to all objects). In this case Hibernate Validator needs to be explicitly told which value
to validate. This can be done via @UnwrapValidatedValue(true)
respectively
@UnwrapValidatedValue(false)
.
Note that it is not specified which of the unwrapper implementations is chosen when more than one implementation is suitable to unwrap a given element. |
Instead of programmatically registering ValidatedValueUnwrapper
types, the fully-qualified names
of one ore more unwrapper implementations can be specified
via the configuration property hibernate.validator.validated_value_handlers
which can be useful when
configuring the default validator factory using the descriptor META-INF/validation.xml (see
Configuring via XML).
11.13.1. Optional unwrapper
Hibernate Validator provides built-in unwrapping for Optional
introduced in Java 8.
The unwrapper is registered automatically in Java 8 environments, and no further configuration is
required. An example of unwrapping an Optional
instance is shown in
Unwrapping Optional
instances.
Optional
instances@Size(min = 3)
private Optional<String> firstName = Optional.of( "John" );
@NotNull
@UnwrapValidatedValue // UnwrapValidatedValue required since otherwise unclear which value to validate
private Optional<String> lastName = Optional.of( "Doe" );
|
11.13.2. JavaFX unwrapper
Hibernate Validator also provides built-in unwrapping for JavaFX property values. The unwrapper is
registered automatically for environments where JavaFX is present, and no further configuration is
required. ObservableValue
and its sub-types are supported.
An example of some of the different ways in which JavaFX
property values can be unwrapped is
shown in Unwrapping JavaFX
properties.
JavaFX
properties@Min(value = 3)
IntegerProperty integerProperty1 = new SimpleIntegerProperty( 4 );
@Min(value = 3)
Property<Number> integerProperty2 = new SimpleIntegerProperty( 4 );
@Min(value = 3)
ObservableValue<Number> integerProperty3 = new SimpleIntegerProperty( 4 );
11.13.3. Unwrapping object graphs
Unwrapping can also be used with object graphs (cascaded validation) as shown in
Unwrapping Optional
prior to cascaded validation via @Valid
.
When validating the object holding the Optional<Person>
, a cascaded validation of the Person
object would be performed.
Optional
prior to cascaded validation via @Valid
@Valid
private Optional<Person> person = Optional.of( new Person() );
public class Person {
@Size(min = 3)
private String name = "Bob";
}
11.14. Providing constraint definitions
Bean Validation allows to (re-)define constraint definitions via XML in its constraint mapping
files. See Mapping constraints via constraint-mappings
for more information and Bean constraints configured via XML
for an example. While this approach is sufficient for many use cases, it has it shortcomings
in others. Imagine for example a constraint library wanting to contribute constraint
definitions for custom types. This library could provide a mapping file with their library, but this
file still would need to be referenced by the user of the library. Luckily there are better ways.
The following concepts are considered experimental at this time. Let us know whether you find them useful and whether they meet your needs. |
11.14.1. Constraint definitions via ServiceLoader
Hibernate Validator allows to utilize Java’s ServiceLoader mechanism to register additional constraint definitions. All you have to do is to add the file javax.validation.ConstraintValidator to META-INF/services. In this service file you list the fully qualified classnames of your constraint validator classes (one per line). Hibernate Validator will automatically infer the constraint types they apply to. See Constraint definition via service file for an example.
# Assuming a custom constraint annotation @org.mycompany.CheckCase
org.mycompany.CheckCaseValidator
To contribute default messages for your custom constraints, place a file ContributorValidationMessages.properties and/or its locale-specific specializations at the root your JAR. Hibernate Validator will consider the entries from all the bundles with this name found on the classpath in addition to those given in ValidationMessages.properties.
This mechanism is also helpful when creating large multi-module applications: Instead of putting all the constraint messages into one single bundle, you can have one resource bundle per module containing only those messages of that module.
11.14.2. Adding constraint definitions programmatically
While the service loader approach works in many scenarios, but not in all (think for example OSGi where service files are not visible), there is yet another way of contributing constraint definitions. You can use the programmatic constraint declaration API - see Adding constraint definitions through the programmatic API.
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.constraintDefinition( ValidPassengerCount.class )
.validatedBy( ValidPassengerCountValidator.class );
Instead of directly adding a constraint mapping to the configuration object, you may use a ConstraintMappingContributor
as detailed in Applying programmatic constraint declarations to the default validator factory. This can be useful when
configuring the default validator factory using META-INF/validation.xml (see
Configuring via XML).
One use case for registering constraint definitions through the programmatic API is the ability to specify an alternative
constraint validator for the Using the programmatic constraint declaration API to register a regular expression based constraint definition for
@URL
|
11.15. Customizing class-loading
There are several cases in which Hibernate Validator needs to load resources or classes given by name:
-
XML descriptors (META-INF/validation.xml as well as XML constraint mappings)
-
classes specified by name in XML descriptors (e.g. custom message interpolators etc.)
-
the ValidationMessages resource bundle
-
the
ExpressionFactory
implementation used for expression based message interpolation
By default Hibernate Validator tries to load these resources via the current thread context classloader. If that’s not successful, Hibernate Validator’s own classloader will be tried as a fallback.
For cases where this strategy is not appropriate (e.g. modularized environments such as OSGi), you may provide a specific classloader for loading these resources when bootstrapping the validator factory:
Validator validator = Validation.byProvider( HibernateValidator.class )
.configure()
.externalClassLoader( classLoader )
.buildValidatorFactory()
.getValidator();
In the case of OSGi, you could e.g. pass the loader of a class from the bundle bootstrapping Hibernate Validator
or a custom classloader implementation which delegates to Bundle#loadClass()
etc.
Call |
11.16. Time providers for @Future and @Past
By default the current system time is used when validating the @Future
and @Past
constraints.
In some cases it can be necessary though to work with another "logical" date rather than the system time,
e.g. for testing purposes or in the context of batch applications which may require to run with
yesterday’s date when re-running a failed job execution.
To address such scenarios, Hibernate Validator provides a custom contract for obtaining the current time, TimeProvider
.
Using a custom TimeProvider
shows an implementation of this contract and its registration when bootstrapping a validator factory.
TimeProvider
package org.hibernate.validator.referenceguide.chapter11.timeprovider;
public class CustomTimeProvider implements TimeProvider {
@Override
public long getCurrentTime() {
Calendar now = GregorianCalendar.getInstance();
return now.getTimeInMillis();
}
}
ValidatorFactory validatorFactory = Validation.byProvider( HibernateValidator.class )
.configure()
.timeProvider( timeProvider )
.buildValidatorFactory();
Alternatively, you can specify the fully-qualified classname of a TimeProvider
implementation using the property
hibernate.validator.time_provider
when configuring the default validator factory via META-INF/validation.xml
(see Configuring via XML).
12. Annotation Processor
Have you ever caught yourself by unintentionally doing things like
-
specifying constraint annotations at unsupported data types (e.g. by annotating a String with
@Past
) -
annotating the setter of a JavaBeans property (instead of the getter method)
-
annotating static fields/methods with constraint annotations (which is not supported)?
Then the Hibernate Validator Annotation Processor is the right thing for you. It helps preventing such mistakes by plugging into the build process and raising compilation errors whenever constraint annotations are incorrectly used.
You can find the Hibernate Validator Annotation Processor as part of the distribution bundle on
Sourceforge or in the
usual Maven repositories such as Maven Central under the GAV
|
12.1. Prerequisites
The Hibernate Validator Annotation Processor is based on the "Pluggable Annotation Processing API" as defined by JSR 269 which is part of the Java Platform since Java 6.
12.2. Features
As of Hibernate Validator 5.4.3.Final the Hibernate Validator Annotation Processor checks that:
-
constraint annotations are allowed for the type of the annotated element
-
only non-static fields or methods are annotated with constraint annotations
-
only non-primitive fields or methods are annotated with
@Valid
-
only such methods are annotated with constraint annotations which are valid JavaBeans getter methods (optionally, see below)
-
only such annotation types are annotated with constraint annotations which are constraint annotations themselves
-
definition of dynamic default group sequence with
@GroupSequenceProvider
is valid -
annotation parameter values are meaningful and valid
-
method parameter constraints in inheritance hierarchies respect the inheritance rules
-
method return value constraints in inheritance hierarchies respect the inheritance rules
12.3. Options
The behavior of the Hibernate Validator Annotation Processor can be controlled using the following processor options:
diagnosticKind
-
Controls how constraint problems are reported. Must be the string representation of one of the values from the enum
javax.tools.Diagnostic.Kind
, e.g.WARNING
. A value ofERROR
will cause compilation to halt whenever the AP detects a constraint problem. Defaults toERROR
. methodConstraintsSupported
-
Controls whether constraints are allowed at methods of any kind. Must be set to
true
when working with method level constraints as supported by Hibernate Validator. Can be set tofalse
to allow constraints only at JavaBeans getter methods as defined by the Bean Validation API. Defaults totrue
. verbose
-
Controls whether detailed processing information shall be displayed or not, useful for debugging purposes. Must be either
true
orfalse
. Defaults tofalse
.
12.4. Using the Annotation Processor
This section shows in detail how to integrate the Hibernate Validator Annotation Processor into command line builds (javac, Ant, Maven) as well as IDE-based builds (Eclipse, IntelliJ IDEA, NetBeans).
12.4.1. Command line builds
javac
When compiling on the command line using javac, specify the JAR hibernate-validator-annotation-processor-5.4.3.Final.jar using the "processorpath" option as shown in the following listing. The processor will be detected automatically by the compiler and invoked during compilation.
javac src/main/java/org/hibernate/validator/ap/demo/Car.java \ -cp /path/to/validation-api-1.1.0.Final.jar \ -processorpath /path/to/hibernate-validator-annotation-processor-5.4.3.Final.jar
Apache Ant
Similar to directly working with javac, the annotation processor can be added as as compiler argument when invoking the javac task for Apache Ant:
<javac srcdir="src/main"
destdir="build/classes"
classpath="/path/to/validation-api-1.1.0.Final.jar">
<compilerarg value="-processorpath" />
<compilerarg value="/path/to/hibernate-validator-annotation-processor-5.4.3.Final.jar"/>
</javac>
Maven
For using the Hibernate Validator annotation processor with Maven, set it up via the annotationProcessorPaths
option like this:
<project>
[...]
<build>
[...]
<plugins>
[...]
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<annotationProcessorPaths>
<path>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
<version>5.4.3.Final</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
[...]
</plugins>
[...]
</build>
[...]
</project>
12.4.2. IDE builds
Eclipse
The annotation processor will automatically be set up for Maven projects configured as described above, provided you have the M2E Eclipse plug-in installed.
For plain Eclipse projects follow these steps to set up the annotation processor:
-
Right-click your project, choose "Properties"
-
Go to "Java Compiler" and make sure, that "Compiler compliance level" is set to "1.6". Otherwise the processor won’t be activated
-
Go to "Java Compiler - Annotation Processing" and choose "Enable annotation processing"
-
Go to "Java Compiler - Annotation Processing - Factory Path" and add the JAR hibernate-validator-annotation-processor-5.4.3.Final.jar
-
Confirm the workspace rebuild
You now should see any annotation problems as regular error markers within the editor and in the "Problem" view:
![annotation processor eclipse](images/annotation_processor_eclipse.png)
IntelliJ IDEA
The following steps must be followed to use the annotation processor within IntelliJ IDEA (version 9 and above):
-
Go to "File", then "Settings",
-
Expand the node "Compiler", then "Annotation Processors"
-
Choose "Enable annotation processing" and enter the following as "Processor path": /path/to/hibernate-validator-annotation-processor-5.4.3.Final.jar
-
Add the processor’s fully qualified name org.hibernate.validator.ap.ConstraintValidationProcessor to the "Annotation Processors" list
-
If applicable add you module to the "Processed Modules" list
Rebuilding your project then should show any erroneous constraint annotations:
![annotation processor intellij](images/annotation_processor_intellij.png)
NetBeans
Starting with version 6.9, also the NetBeans IDE supports using annotation processors within the IDE build. To do so, do the following:
-
Right-click your project, choose "Properties"
-
Go to "Libraries", tab "Processor", and add the JAR hibernate-validator-annotation-processor-5.4.3.Final.jar
-
Go to "Build - Compiling", select "Enable Annotation Processing" and "Enable Annotation Processing in Editor". Add the annotation processor by specifying its fully qualified name org.hibernate.validator.ap.ConstraintValidationProcessor
Any constraint annotation problems will then be marked directly within the editor:
![annotation processor netbeans](images/annotation_processor_netbeans.png)
12.5. Known issues
The following known issues exist as of May 2010:
-
HV-308: Additional validators registered for a constraint using XML are not evaluated by the annotation processor.
-
Sometimes custom constraints can’t be properly evaluated when using the processor within Eclipse. Cleaning the project can help in these situations. This seems to be an issue with the Eclipse JSR 269 API implementation, but further investigation is required here.
-
When using the processor within Eclipse, the check of dynamic default group sequence definitions doesn’t work. After further investigation, it seems to be an issue with the Eclipse JSR 269 API implementation.
13. Further reading
Last but not least, a few pointers to further information.
A great source for examples is the Bean Validation TCK which is available for anonymous access on GitHub. In particular the TCK’s tests might be of interest. The JSR 349 specification itself is also a great way to deepen your understanding of Bean Validation resp. Hibernate Validator.
If you have any further questions to Hibernate Validator or want to share some of your use cases have a look at the Hibernate Validator Wiki and the Hibernate Validator Forum.
In case you would like to report a bug use Hibernate’s Jira instance. Feedback is always welcome!