Hibernate.orgCommunity Documentation
JSR 349 Reference Implementation
Reference Guide
5.1.3.Final
Copyright © 2009 - 2013 Red Hat, Inc. & Gunnar Morling
2014-10-22
- Preface
- 1. Getting started
- 2. Declaring and validating bean constraints
- 3. Declaring and validating method constraints
- 4. Interpolating constraint error messages
- 5. Grouping constraints
- 6. Creating custom constraints
- 7. Configuring via XML
- 8. Bootstrapping
- 9. Using constraint metadata
- 10. Integrating with other frameworks
- 11. Hibernate Validator Specifics
- 12. Annotation Processor
- 13. Further reading
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.
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.
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.
This chapter will show you how to get started with Hibernate Validator, the reference implementation (RI) of Bean Validation. For the following quickstart you need:
A JDK >= 6
An Internet connection (Maven has to download all required libraries)
In order to use Hibernate Validator within a Maven project, simply
add the following dependency to your pom.xml:
Example 1.1. Hibernate Validator Maven dependency
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.1.3.Final</version>
</dependency>
This transitively pulls in the dependency to the Bean Validation API
(javax.validation:validation-api:1.1.0.Final).
Hibernate Validator requires an implementation of the Unified Expression Language (JSR 341) for evaluating dynamic expressions in constraint violation messages (seeSection 4.1, “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 341reference implementation:
Example 1.2. Maven dependencies for Unified EL reference implementation
<dependency>
<groupId>javax.el</groupId>
<artifactId>javax.el-api</artifactId>
<version>2.2.4</version>
</dependency>
<dependency>
<groupId>org.glassfish.web</groupId>
<artifactId>javax.el</artifactId>
<version>2.2.4</version>
</dependency>
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:
Example 1.3. Hibernate Validator CDI portable extension Maven dependency
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-cdi</artifactId>
<version>5.1.3.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 inSection 10.3, “CDI”.
Lets dive directly into an example to see how to apply constraints.
Example 1.4. Class
Car
annotated with
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 be
nulllicensePlate must never be
nulland must be between 2 and 14 characters longseatCount must be at least 2
Tip
You can find the complete source code of all examples used in this reference guide in the Hibernate Validator source repository on GitHub.
To perform a validation of these constraints, you use a
Validator
instance. Let's have a look at a unit
test forCar:
Example 1.5. Class
CarTest
showing validation
examples
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 setUp() {
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
@NotNullconstraint on manufacturer is violated inmanufacturerIsNull()The
@Sizeconstraint on licensePlate is violated inlicensePlateTooShort()The
@Minconstraint on seatCount 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.
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 inChapter 13, Further reading.
To learn more about the validation of beans and properties, just continue readingChapter 2, Declaring and validating bean constraints. If you are interested in using Bean Validation for the validation of method pre- and postcondition refer toChapter 3, Declaring and validating method constraints. In case your application has specific validation requirements have a look at Chapter 6, Creating custom constraints.
In this chapter you will learn how to declare (see Section 2.1, “Declaring bean constraints”) and validate (see Section 2.2, “Validating bean constraints”) bean constraints. Section 2.3, “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 Chapter 3, Declaring and validating method 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
Note
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 java.lang.annotation.Target
annotation in the constraint annotation itself determines on which
elements a constraint can be placed. See Chapter 6, Creating custom constraints for more information.
Constraints can be expressed by annotating a field of a class. Example 2.1, “Field-level constraints” shows a field level configuration example:
Example 2.1. Field-level constraints
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.
Tip
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.
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. Example 2.2, “Property-level constraints” uses the same entity as in Example 2.1, “Field-level constraints”, however, property level constraints are used.
Example 2.2. Property-level constraints
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;
}
}
Note
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.
Tip
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.
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 Example 2.3, “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 Section 6.2, “Class-level constraints” to learn in detail how to implement this custom constraint.
Example 2.3. Class-level constraint
package org.hibernate.validator.referenceguide.chapter02.classlevel;
@ValidPassengerCount
public class Car {
private int seatCount;
private List<Person> passengers;
//...
}
When a class implements an interface or extends another class, all constraint annotations declared on the supertype 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:
Example 2.4. Constraint inheritance
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.
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
Example 2.5, “Cascaded validation”.
Example 2.5. 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,ListandSet)implement
java.util.Map
can be annotated with @Valid, which will
cause each contained element to be validated, when the parent object is
validated.
Example 2.6. Cascaded validation of a collection
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 Example 2.6, “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.
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.
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():
Example 2.7. Validation#buildDefaultValidatorFactory()
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
This bootstraps a validator in the default configuration. Refer to
Chapter 8, Bootstrapping to learn more about the
different bootstrapping methods and how to obtain a specifically
configured Validator instance.
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 Chapter 5, Grouping constraints.
Use the validate() method to perform
validation of all constraints of a given bean. Example 2.8, “Using Validator#validate()” shows the validation of an
instance of the Car class from Example 2.2, “Property-level constraints” which fails to satisfy the
@NotNull constraint on the
manufacturer property. The validation call
therefore returns one ConstraintViolation
object.
Example 2.8. Using 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() );
With help of the validateProperty() you
can validate a single named property of a given object. The property
name is the JavaBeans property name.
Example 2.9. Using
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() );
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:
Example 2.10. Using
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() );
Note
@Valid is not honored by
validateProperty() or
validateValue().
Validator#validateProperty() is for
example used in the integration of Bean Validation into JSF 2 (see
Section 10.2, “JSF & Seam”) to perform a validation
of the values entered into a form before they are propagated to the
model.
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.
Table 2.1, “The various ConstraintViolation
methods” gives an overview of these
methods. The values in the "Example" column refer to Example 2.8, “Using Validator#validate()”.
Table 2.1. The various ConstraintViolation
methods
| Method | Usage | Example |
|---|---|---|
getMessage() | The interpolated error message | "may not be null" |
getMessageTemplate() | The non-interpolated error message | "{... NotNull.message}" |
getRootBean() | The root bean being validated | car |
getRootBeanClass() | The class of the root bean being validated | 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 | car |
getPropertyPath() | The property path to the validated value from root bean | contains one node with kind
PROPERTY and name "manufacturer" |
getInvalidValue() | The value failing to pass the constraint | null |
getConstraintDescriptor() | Constraint metadata reported to fail | descriptor for @NotNull |
Hibernate Validator comprises a basic set of commonly used constraints. These are foremost the constraints defined by the Bean Validation specification (see Table 2.2, “Bean Validation constraints”). Additionally, Hibernate Validator provides useful custom constraints (see Table 2.3, “Custom constraints” and Table 2.4, “Custom country specific constraints”).
Table 2.2, “Bean Validation constraints” shows purpose and supported data types 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 column "Hibernate metadata impact").
Note
Hibernate Validator allows some constraints to be applied to
more data types than required by the Bean Validation specification
(e.g. @Max can be applied to
Strings). Relying on this feature can impact
portability of your application between Bean Validation
providers.
Table 2.2. Bean Validation constraints
| Annotation | Supported data types | Use | Hibernate metadata impact |
|---|---|---|---|
@AssertFalse | Boolean,
boolean | Checks that the annotated element is
false | None |
@AssertTrue | Boolean,
boolean | Checks that the annotated element is
true | None |
@DecimalMax(value=,
inclusive=) | BigDecimal,
BigInteger,
CharSequence,
byte, short,
int, long and the
respective wrappers of the primitive types; Additionally
supported by HV: any sub-type of
Number | 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 the
BigDecimal string representation. | None |
@DecimalMin(value=,
inclusive=) | BigDecimal,
BigInteger,
CharSequence,
byte, short,
int, long and the
respective wrappers of the primitive types; Additionally
supported by HV: any sub-type of
Number | 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 the
BigDecimal string representation. | None |
@Digits(integer=,
fraction=) | BigDecimal,
BigInteger,
CharSequence,
byte, short,
int, long and the
respective wrappers of the primitive types; Additionally
supported by HV: any sub-type of
Number | Checks whether the annoted value is a number having up to
integer digits and
fraction fractional digits | Defines column precision and scale |
@Future | java.util.Date,
java.util.Calendar; Additionally
supported by HV, if the Joda Time
date/time API is on the class path: any implementations of
ReadablePartial and
ReadableInstant | Checks whether the annotated date is in the future | None |
@Max(value=) | BigDecimal,
BigInteger, byte,
short, int,
long and the respective wrappers of the
primitive types; Additionally supported by HV: any sub-type of
CharSequence (the numeric value
represented by the character sequence is evaluated), any
sub-type of Number | Checks whether the annotated value is less than or equal to the specified maximum | Adds a check constraint on the column |
@Min(value=) | BigDecimal,
BigInteger, byte,
short, int,
long and the respective wrappers of the
primitive types; Additionally supported by HV: any sub-type of
CharSequence (the numeric value
represented by the char sequence is evaluated), any sub-type of
Number | Checks whether the annotated value is higher than or equal to the specified minimum | Adds a check constraint on the column |
@NotNull | Any type | Checks that the annotated value is not
null. | Column(s) are not nullable |
@Null | Any type | Checks that the annotated value is
null | None |
@Past | java.util.Date,
java.util.Calendar; Additionally
supported by HV, if the Joda Time
date/time API is on the class path: any implementations of
ReadablePartial and
ReadableInstant | Checks whether the annotated date is in the past | None |
@Pattern(regex=,
flag=) | CharSequence | Checks if the annotated string matches the regular
expression regex considering the given
flag match | None |
@Size(min=, max=) | CharSequence,
Collection, Map
and arrays | Checks if the annotated element's size is between min and max (inclusive) | Column length will be set to
max |
@Valid | Any non-primitive type | 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. | None |
Note
On top of the parameters indicated in Table 2.2, “Bean Validation constraints” each constraint has the parameters
message, groups and
payload. This is a requirement of the Bean
Validation specification.
In addition to the constraints defined by the Bean Validation API
Hibernate Validator provides several useful custom constraints which are
listed in Table 2.3, “Custom constraints”. With one exception
also these constraints apply to the field/property level, only
@ScriptAssert is a class-level constraint.
Table 2.3. Custom constraints
| Annotation | Supported data types | Use | Hibernate metadata impact |
|---|---|---|---|
@CreditCardNumber(ignoreNonDigitCharacters=) | CharSequence | 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 is false. | None |
@EAN | CharSequence | Checks that the annotated character sequence is a valid
EAN
barcode. type determines the type of
barcode. The default is EAN-13. | None |
@Email | CharSequence | Checks whether the specified character sequence is a
valid email address. The optional parameters
regexp and flags
allow to specify an additional regular expression (including
regular expression flags) which the email must match. | None |
@Length(min=, max=) | CharSequence | Validates that the annotated character sequence is
between min and
max included | Column length will be set to
max |
@LuhnCheck(startIndex=,
endIndex=,
checkDigitIndex=,
ignoreNonDigitCharacters=) | CharSequence | Checks that the digits within the annotated character
sequence pass the Luhn checksum algorithm (see also Luhn
algorithm). startIndex and
endIndex 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. | None |
@Mod10Check(multiplier=,
weight=, startIndex=,
endIndex=,
checkDigitIndex=,
ignoreNonDigitCharacters=) | CharSequence | 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 and
endIndex 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. | None |
@Mod11Check(threshold=,
startIndex=, endIndex=,
checkDigitIndex=,
ignoreNonDigitCharacters=,
treatCheck10As=,
treatCheck11As=) | CharSequence | 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
and treatCheck11As 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
acheckDigitIndex and
ignoreNonDigitCharacters carry the same
semantics as in @Mod10Check. | None |
@NotBlank | CharSequence | 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 whitespaces are
ignored. | None |
@NotEmpty | CharSequence,
Collection, Map
and arrays | Checks whether the annotated element is not
null nor empty | None |
@Range(min=, max=) | BigDecimal,
BigInteger,
CharSequence,
byte, short,
int, long and the
respective wrappers of the primitive types | Checks whether the annotated value lies between (inclusive) the specified minimum and maximum | None |
@SafeHtml(whitelistType=,
additionalTags=,
additionalTagsWithAttributes=) | CharSequence | Checks whether the annotated value contains
potentially malicious fragments such as
With the
| None |
@ScriptAssert(lang=,
script=, alias=) | Any type | 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 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. | None |
@URL(protocol=, host=,
port= regexp=,
flags=) | CharSequence | Checks if the annotated character sequence is a valid URL
according to RFC2396. If any of the optional parameters
protocol, host or
port are specified, the corresponding URL
fragments must match the specified values. The optional
parameters regexp and
flags allow to specify an additional
regular expression (including regular expression flags) which
the URL must match. | None |
Hibernate Validator offers also some country specific constraints, e.g. for the validation of social security numbers.
Note
If you have to implement a country specific constraint, consider making it a contribution to Hibernate Validator!
Table 2.4. Custom country specific constraints
| Annotation | Supported data types | Use | Country | Hibernate metadata impact |
|---|---|---|---|---|
@CNPJ | CharSequence | Checks that the annotated character sequence represents a Brazilian corporate tax payer registry number (Cadastro de Pessoa Juríeddica) | Brazil | None |
@CPF | CharSequence | Checks that the annotated character sequence represents a Brazilian individual taxpayer registry number (Cadastro de Pessoa Fídsica) | Brazil | None |
@TituloEleitoral | CharSequence | Checks that the annotated character sequence represents a Brazilian voter ID card number (Título Eleitoral) | Brazil | None |
Tip
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 Chapter 6, Creating custom 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)
Note
For the purpose of this reference guide, the term method constraint refers to both, method and constructor constraints, if not stated otherwise. Ocassionally, the term executable is used when referering 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
IllegalArgumentExceptionsor similar), resulting in less code to write and maintainan 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
Tip
In order to make annotations show up in the JavaDoc of annoted
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.
You specify the preconditions of a method or constructor by adding constraint annotations to its parameters as demonstrated in Example 3.1, “Declaring method and constructor parameter constraints”.
Example 3.1. 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 the
RentalCarconstructor must not benullWhen invoking the
rentCar()method, the given customer must not benull, the rental's start date must not benulland must be in the future and 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 Section 3.2, “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.
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 Example 3.2, “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.
Example 3.2. Declaring a cross-parameter constraint
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 Section 6.3, “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 Example 3.3, “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.
Example 3.3. Specifying a constraint's target
package org.hibernate.validator.referenceguide.chapter03.crossparameter.constrainttarget;
public class Garage {
@ELAssert(expression = "...", validationAppliesTo = ConstraintTarget.PARAMETERS)
public Car buildCar(List<Part> parts) {
//...
}
@ELAssert(expression = "...", validationAppliesTo = ConstraintTarget.RETURN_VALUE)
public Car paintCar(int color) {
//...
}
}
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.
The postconditions of a method or constructor are declared by adding constraint annotations to the executable as shown in Example 3.4, “Declaring method and constructor return value constraints”.
Example 3.4. 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() {
//...
}
}
The following constraints apply to the executables of
RentalStation:
Any newly created
RentalStationobject must satisfy the@ValidRentalStationconstraintThe customer list returned by
getCustomers()must not benulland must contain at least on element
Similar to the cascaded validation of JavaBeans properties (see
Section 2.1.5, “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 Example 3.5, “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.
Example 3.5. Marking executable parameters and return values 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) {
//...
}
}
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.Iterableor implements
java.util.Map
each contained element gets validated. So when validating the
arguments of the checkCars() method in Example 3.6, “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 objects is invalid.
Example 3.6. List-typed method parameter marked for cascaded validation
package org.hibernate.validator.referenceguide.chapter03.cascaded.collection;
public class Garage {
public boolean checkCars(@Valid @NotNull List<Car> cars) {
//...
}
}
When declaring method constraints in inheritance hierarchies, it is important to be aware of the following rules:
The preconditions to be satisified 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). Example 3.7, “Illegal method parameter constraint in subtype” shows a violation of this rule.
Example 3.7. Illegal method parameter constraint in subtype
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 Example 3.8, “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.
Example 3.8. Illegal method parameter constraint in parallel types of a hierarchy
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 {
public 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 Example 3.9, “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.
Example 3.9. Return value constraints on supertype and subtype method
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() {
//...
}
}
If the validation engine detects a violation of any of the
aforementioned rules, a
ConstraintDeclarationException will be
raised.
Note
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.
The validation of method constraints is done using the
ExecutableValidator interface.
In Section 3.2.1, “Obtaining an ExecutableValidator
instance” you will
learn how to obtain an ExecutableValidator instance
while Section 3.2.2, “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.
You can retrieve an ExecutableValidator
instance via Validator#forExecutables() as shown
in Example 3.10, “Obtaining an ExecutableValidator”.
Example 3.10. Obtaining an ExecutableValidator
ValidatorFactory 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 Chapter 8, Bootstrapping, for instance in order to use a specific parameter name provider (see Section 8.2.4, “ParameterNameProvider”).
The ExecutableValidator interface offers
altogether four methods:
validateParameters()andvalidateReturnValue()for method validationvalidateConstructorParameters()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 Example 3.11, “Class Car with constrained methods and
constructors”.
Example 3.11. Class Car with constrained methods and
constructors
package 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() {
//...
}
}
The method validateParameters() is used
to validate the arguments of a method invocation. Example 3.12, “Using
ExecutableValidator#validateParameters()” shows an
example. The validation results in a violation of the
@Max constraint on the parameter of the
drive() method.
Example 3.12. Using
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.
Using validateReturnValue() the return
value of a method can can be validated. The validation in Example 3.13, “Using
ExecutableValidator#validateReturnValue()” yields
one constraint violation since the
getPassengers() method is expect to return at
least one Passenger object.
Example 3.13. Using
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 );
The arguments of constructor invocations can be validated with
validateConstructorParameters() as shown in
method Example 3.14, “Using
ExecutableValidator#validateConstructorParameters()”.
Due to the @NotNull constraint on the
manufacturer parameter, the validation call returns
one constraint violation.
Example 3.14. Using
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 );
Finally, by using
validateConstructorReturnValue() you can
valide a constructor's return value. In Example 3.15, “Using
ExecutableValidator#validateConstructorReturnValue()”,
validateConstructorReturnValue() returns one
constraint violation, since the Car object
returned by the constructor doesn't satisfy the
@ValidRacingCar constraint (not shown).
Example 3.15. Using
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 );
In addition to the methods introduced in Section 2.2.3, “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 Example 3.16, “Retrieving method and parameter information”.
Example 3.16. 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 Section 8.2.4, “ParameterNameProvider”) and defaults to
arg0, arg1 etc.
In addition to the built-in bean and property-level constraints
discussed in Section 2.3, “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
Section 8.2.4, “ParameterNameProvider”). Example 3.17, “Using @ParameterScriptAssert” shows how the validation logic
of the @LuggageCountMatchesPassengerCount
constraint from Example 3.2, “Declaring a cross-parameter constraint”
could be expressed with the help of
@ParameterScriptAssert.
Example 3.17. Using @ParameterScriptAssert
package org.hibernate.validator.referenceguide.chapter03.parametersscriptassert;
public class Car {
@ParameterScriptAssert(lang = "javascript", script = "arg1.size() <= arg0.size() * 2")
public void load(List<Person> passengers, List<PieceOfLuggage> luggage) {
//...
}
}
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.
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
Example 4.1, “Specifying a message descriptor using the
message attribute”.
Example 4.1. 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 namedValidationMessages.propertiesto the classpath. You can also create localized error messages by providing locale specific variations of this bundle, such asValidationMessages_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 Section 4.1.2, “Interpolation with message expressions” to learn more about the usage of Unified EL in error messages.
Tip
You can find the formal definition of the interpolation algorithm in section 5.3.1.1 of the Bean Validation specification.
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$\\is considered as the literal\
As of Hibernate Validator 5 (Bean Validation 1.1) it is possible to use the Unified Expression Language (as defined by JSR 341) in constraint violation messages. This allows to define error messages based on conditional logic and also enables advanced formatting options. The validation engine makes the following objects available in the EL context:
the attribute values of the constraint mapped to the attribute names
the currently validated value (property, bean, method parameter etc.) under the name
validatedValuea bean mapped to the name
formatterexposing the var-arg methodformat(String format, Object... args)which behaves likejava.util.Formatter.format(String format, Object... args).
The following section provides several examples for using EL expressions in error messages.
Example 4.2, “Specifying message descriptors” shows how to make use of the different options for specifying message descriptors.
Example 4.2. Specifying message descriptors
package org.hibernate.validator.referenceguide.chapter04.complete;
public class Car {
@NotNull
private String manufacturer;
@Size(
min = 2,
max = 14,
message = "The license plate '${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 ${value}")
private BigDecimal price;
public Car(
String manufacturer,
String licensePlate,
int seatCount,
double topSpeed,
BigDecimal price) {
this.manufacturer = manufacturer;
this.licensePlate = licensePlate;
this.seatCount = seatCount;
this.topSpeed = topSpeed;
this.price = price;
}
//getters and setters ...
}
Validating an invalid Car instance yields
constraint violations with the messages shown by the assertions in Example 4.3, “Expected error messages”:
the
@NotNullconstraint on themanufacturerfield causes the error message "may not be null", as this is the default message defined by the Bean Validation specification and no specific descriptor is given in themessageattributethe
@Sizeconstraint on thelicensePlatefield shows the interpolation of message parameters ({min},{max}) and how to add the validated value to the error message using the EL expression${validatedValue}the
@Minconstraint onseatCountdemonstrates 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
@DecimalMaxconstraint ontopSpeedshows how to format the validated value using theformatterobjectfinally, the
@DecimalMaxconstraint onpriceshows that parameter interpolation has precedence over expression evaluation, causing the$sign to show up in front of the maximum price
Tip
Only actual constraint attributes can be interpolated using
message parameters in the form {attributeName}. When
referring to the validated value or custom expression variables added
to the interpolation context (see Section 11.6.1, “HibernateConstraintValidatorContext”), an EL
expression in the form ${attributeName} must be
used.
Example 4.3. Expected error messages
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 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 );
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 Section 7.1, “Configuring the validator factory in
validation.xml”) or by passing it when
bootstrapping a ValidatorFactory or
Validator (see Section 8.2.1, “MessageInterpolator” and Section 8.3, “Configuring a Validator”, respectively).
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 Example 4.4, “Using a specific resource bundle”.
Example 4.4. 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 fallback 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. Example 4.5, “Using
AggregateResourceBundleLocator” shows how to
use AggregateResourceBundleLocator.
Example 4.5. Using
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.
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.
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 5.1, “Person” has a
@NotNull constraint on name.
Since no group is specified for this annotation the default group
javax.validation.groups.Default is assumed.
Note
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 javax.validation.groups.Default is
assumed.
Example 5.1. 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 Example 5.2, “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.
Tip
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.
Example 5.2. Driver
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 (Example 5.3, “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.
Example 5.3. Car
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;
}
// 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 and Car.seatCount all belong to the
DefaultgroupThe constraints on Driver.age and Driver.hasDrivingLicense belong to
DriverChecksThe constraint on Car.passedVehicleInspection belongs to the group
CarChecks
Example 5.4, “Using validation groups” shows how passing different
group combinations to the Validator#validate()
method results in different validation results.
Example 5.4. Using validation groups
// 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 ).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 Example 5.4, “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.
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 Example 5.4, “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 Example 5.5, “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.
Example 5.5. Defining a group sequence
package org.hibernate.validator.referenceguide.chapter05;
@GroupSequence({ Default.class, CarChecks.class, DriverChecks.class })
public interface OrderedChecks {
}
Warning
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
GroupDefinitionException is raised.
You then can use the new sequence as shown in in Example 5.6, “Using a group sequence”.
Example 5.6. 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() );
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.
Example 5.7, “Class RentalCar with redefined default
group” introduces a new class
RentalCar with a redefined default group.
Example 5.7. Class RentalCar with redefined default
group
package 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 Example 5.8, “Validating an object with redefined default group”.
Example 5.8. 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() );
Note
Since there must no cyclic dependency in the group and group
sequence definitions one cannot just add
Default to the sequence redefining
Default for a class. Instead the class itself
has to be added!
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 Section 5.4, “Group conversion”).
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 Example 5.9, “Implementing and using a default group sequence
provider”.
Example 5.9. 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;
}
}
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 Example 5.10, “@ConvertGroup usage”. Here
@GroupSequence({ CarChecks.class, Car.class }) is used to
combine the car related constraints under the
Default group (see Section 5.3, “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.
Example 5.10. @ConvertGroup usage
package 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;
}
// 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;
}
// getters and setters ...
}
As a result the validation in Example 5.11, “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.
Example 5.11. Test case for @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:
@ConvertGroupmust only be used in combination with@Valid. If used without, aConstraintDeclarationExceptionis thrown.It is not legal to have multiple conversion rules on the same element with the same
fromvalue. In this case, aConstraintDeclarationExceptionis raised.The
fromattribute must not refer to a group sequence. AConstraintDeclarationExceptionis raised in this situation.
Note
Rules are not executed recursively. The first matching
conversion rule is used and subsequent rules are ignored. For example
if a set of @ConvertGroup declarations chains
group A to B and B to C, the group A will be converted to B and not to
C.
The Bean Validation API defines a whole set of standard constraint
annotations such as @NotNull,
@Size etc. In cases where these buit-in constraints
are not sufficient, you cean easily create custom constraints tailored to
your specific validation requirements.
To create a custom constraint, the following three steps are required:
Create a constraint annotation
Implement a validator
Define a default error message
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 Chapter 1, 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:
Example 6.1. Enum CaseMode to express upper vs. lower
case
package 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:
Example 6.2. Defining the @CheckCase constraint
annotation
package 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 Chapter 5, Grouping constraints). This must default to an empty array of type
Class<?>.an attribute
payloadthat 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
ContactDetailsinstance access the severity of a constraint usingConstraintViolation.getConstraintDescriptor().getPayload()and adjust its behaviour 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.@CheckCasemay be used on fields (element typeFIELD), JavaBeans properties as well as method return values (METHOD) and method/constructor parameters (PARAMETER). The element typeANNOTATION_TYPEallows for the creation of composed constraints (see Section 6.4, “Constraint composition”) based on@CheckCase.When creating a class-level constraint (see Section 2.1.3, “Class-level constraints”), the element type
TYPEwould have to be used. Constraints targetting the return value of a constructor need to support the element typeCONSTRUCTOR. Cross-parameter constraints (see Section 6.3, “Cross-parameter constraints”) which are used to validate all the parameters of a method or constructor together, must supportMETHODorCONSTRUCTOR, 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@CheckCasewill 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.
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:
Example 6.3. Implementing a constraint validator for the constraint
@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.
Example 6.3, “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:
Example 6.4. Using ConstraintValidatorContext to
define custom error messages
package 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.chapter03." +
"constraintvalidatorcontext.CheckCase.message}"
)
.addConstraintViolation();
}
return isValid;
}
}
Example 6.4, “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.
Tip
It is important to add each configured constraint violation by
calling addConstraintViolation(). Only
after that the new constraint violation will be created.
Refer to Section 6.2.1, “Custom property paths” to
learn how to use the ConstraintValidatorContext
API to control the property path of constraint violations for
class-level constraints.
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 Section 4.1, “Default message interpolation”):
Example 6.5. Defining a custom error message for the
CheckCase constraint
org.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.
You can now use the constraint in the Car
class from the Chapter 1, Getting started chapter to
specify that the licensePlate field should only
contain upper-case strings:
Example 6.6. Applying the @CheckCase
constraint
package 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, Example 6.7, “Validating objects with the @CheckCase
constraint” demonstrates
how validating a Car object with an invalid
license plate causes the @CheckCase constraint to
be violated.
Example 6.7. Validating objects with the @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() );
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. Example 6.8, “Implementing a class-level constraint” shows constraint
annotation and validator of the
@ValidPassengerCount constraint you already saw in
use in Example 2.3, “Class-level constraint”.
Example 6.8. Implementing a 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.
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.
Example 6.9, “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.
Example 6.9. Adding a new ConstraintViolation with
custom property path
package 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;
}
}
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:
Example 6.10. Cross-parameter constraint
package org.hibernate.validator.referenceguide.chapter06.crossparameter;
@Constraint(validatedBy = ConsistentDateParameterValidator.class)
@Target({ METHOD, CONSTRUCTOR, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Documented
public @interface ConsistentDateParameters {
String message() default "{org.hibernate.validator.referenceguide.chapter06." +
"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 Example 6.11, “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 Section 6.4, “Constraint composition”).
Note
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
@ConsistentDateParameters - which make the
constraint target apparent.
Example 6.11. Generic and cross-parameter constraint
package org.hibernate.validator.referenceguide.chapter06.crossparameter;
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class ConsistentDateParameterValidator 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.
Tip
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 ConstraintValidatorContext passed to
isValid() and add a parameter node by calling
addParameterNode(). In the example you could
use this to create a constraint violation on the end date parameter of
the validated method.
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 Example 6.12, “Generic and cross-parameter constraint”.
Example 6.12. 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.chapter06." +
"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 Example 6.13, “Specifying the target for a generic and cross-parameter
constraint”.
Example 6.13. 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) {
//...
}
Looking at the licensePlate field of the
Car class in Example 6.6, “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. Example 6.14, “Creating a composing constraint
@ValidLicensePlate” shows a composed constraint
annotation which comprises the constraints
@NotNull, @Size and
@CheckCase:
Example 6.14. Creating a composing constraint
@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:
Example 6.15. Application of composing constraint
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:
Example 6.16. Using @ReportAsSingleViolation
//...
@ReportAsSingleViolation
public @interface ValidLicensePlate {
String message() default "{org.hibernate.validator.referenceguide.chapter06." +
"constraintcomposition.ValidLicensePlate.message}";
Class<?>[] groups() default { };
Class<? extends Payload>[] payload() default { };
}
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.
Note
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.
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. Example 7.1, “validation-configuration-1.1.xsd” shows a model view of the XML
schema to which validation.xml has to adhere.
Example 7.2, “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
Section 8.2, “Configuring a ValidatorFactory”.
Example 7.2. 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>
Warning
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
Section 8.2, “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 Chapter 3, 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 Section 11.2, “Fail fast mode”).
Expressing constraints in XML is possible via files adhering to the
schema seen in Example 7.3, “validation-mapping-1.1.xsd”. Note that
these mapping files are only processed if listed via
constraint-mapping in
validation.xml.
Example 7.4, “Bean constraints configured via XML” shows how the classes
Car and RentalCar from Example 5.3, “Car” resp. Example 5.7, “Class RentalCar with redefined default
group” could
be mapped in XML.
Example 7.4. Bean constraints configured via 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>
Example 7.5, “Method constraints configured via XML” shows how the constraints from Example 3.1, “Declaring method and constructor parameter constraints”, Example 3.4, “Declaring method and constructor return value constraints” and Example 3.3, “Specifying a constraint's target” can be expressed in XML.
Example 7.5. Method constraints configured via 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.
Warning
A given entity 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 ValidationException
is thrown.
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 Section 5.3, “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 Section 5.4, “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
ConstraintValidators 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 elements
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.
In Section 2.2.1, “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.
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.
Example 8.1, “Bootstrapping default ValidatorFactory and Validator” shows how to obtain a validator from the default validator factory:
Example 8.1. Bootstrapping default ValidatorFactory and
Validator
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
Tip
The generated ValidatorFactory and
Validator instances are thread-safe and can be
cached. As Hibernate Validator uses the factory as context for caching
constraint metadata it is recommended to work with one factory instance
within an application.
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 Example 8.2, “Bootstrapping ValidatorFactory and
Validator using a specific provider”.
Example 8.2. Bootstrapping ValidatorFactory and
Validator using a specific provider
ValidatorFactory 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 Example 8.3, “Retrieving the default ValidatorFactory for configuration”.
Example 8.3. Retrieving the default ValidatorFactory
for configuration
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Note
If a ValidatorFactory instance is no longer
in use, it should be disposed by calling
ValidatorFactory#close(). This will free any
resources possibly allocated by the factory.
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 Example 8.4, “Using a custom
ValidationProviderResolver”.
Example 8.4. Using a custom
ValidationProviderResolver
package org.hibernate.validator.referenceguide.chapter08;
public class OsgiServiceDiscoverer implements ValidationProviderResolver {
@Override
public List<ValidationProvider<?>> getValidationProviders() {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.providerResolver( new OsgiServiceDiscoverer() )
.configure()
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
By default validator factories retrieved from
Validation and any validators they create are
configured as per the XML descriptor
META-INF/validation.xml (see Chapter 7, 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.
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
Chapter 4, 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
Example 8.5, “Using a custom
MessageInterpolator”.
Example 8.5. Using a custom
MessageInterpolator
package org.hibernate.validator.referenceguide.chapter08;
public class MyMessageInterpolator implements MessageInterpolator {
@Override
public String interpolate(String messageTemplate, Context context) {
//...
}
@Override
public String interpolate(String messageTemplate, Context context, Locale locale) {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.messageInterpolator( new MyMessageInterpolator() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
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.
Example 8.6, “Using a custom
TraversableResolver” shows how to
use a custom traversable resolver implementation.
Example 8.6. Using a custom
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) {
//...
}
@Override
public boolean isCascadable(
Object traversableObject,
Node traversableProperty,
Class<?> rootBeanType,
Path pathToTraversableObject,
ElementType elementType) {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.traversableResolver( new MyTraversableResolver() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Hibernate Validator provides two
TraversableResolvers out of the box which will be
enabled automatically depending on your environment. The first is
DefaultTraversableResolver which will always
return true for
isReachable() and
isTraversable(). The second is
JPATraversableResolver which gets enabled when
Hibernate Validator is used in combination with JPA 2.
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
Section 6.1.2, “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
Example 8.7, “Using a custom
ConstraintValidatorFactory”.
Example 8.7. Using a custom
ConstraintValidatorFactory
package org.hibernate.validator.referenceguide.chapter08;
public class MyConstraintValidatorFactory implements ConstraintValidatorFactory {
@Override
public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key) {
//...
}
@Override
public void releaseInstance(ConstraintValidator<?, ?> instance) {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.constraintValidatorFactory( new MyConstraintValidatorFactory() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Warning
Any constraint implementations relying on
ConstraintValidatorFactory behaviors specific
to an implementation (dependency injection, no no-arg constructor and
so on) are not considered portable.
Note
ConstraintValidatorFactory
implementations should not cache validator instances as the state of
each instance can be altered in the
initialize() method.
In case a method or constructor parameter constraint is violated,
the ParameterNameProvider interface is used to
retrieve the parameter's name and make it available to the user via the
constraint violation's property path.
The default implementation returns parameter names in the form
arg0, arg1 etc., while custom
implementations could e.g. be based on parameter annotations, debug
symbols or a feature for retrieving parameter names at runtime possibly
provided by future Java versions.
Custom ParameterNameProvider
implementations are used as demonstrated in Example 8.8, “Using a custom
ParameterNameProvider”.
Example 8.8. Using a custom
ParameterNameProvider
package org.hibernate.validator.referenceguide.chapter08;
public class MyParameterNameProvider implements ParameterNameProvider {
@Override
public List<String> getParameterNames(Constructor<?> constructor) {
//...
}
@Override
public List<String> getParameterNames(Method method) {
//...
}
}
ValidatorFactory validatorFactory = Validation.byDefaultProvider()
.configure()
.parameterNameProvider( new MyParameterNameProvider() )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Tip
Hibernate Validator comes with a custom
ParameterNameProvider implementation based on
the ParaNamer
library which provides several ways for obtaining parameter names at
runtime. Refer to Section 11.7, “ParaNamer based
ParameterNameProvider” to learn more
about this specific implementation.
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
Example 8.9, “Adding constraint mapping streams”). Note that the passed
input stream(s) must adhere to the XML schema for constraint mappings
presented in Section 7.2, “Mapping constraints via
constraint-mappings”.
Example 8.9. Adding constraint mapping streams
InputStream constraintMapping1 = ...;
InputStream constraintMapping2 = ...;
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.
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 Example 8.10, “Setting Hibernate Validator specific options”.
Example 8.10. 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:
Example 8.11. Enabling a Hibernate Validator specific option via
addProperty()
ValidatorFactory validatorFactory = Validation.byProvider( HibernateValidator.class )
.configure()
.addProperty( "hibernate.validator.fail_fast", "true" )
.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Refer to Section 11.2, “Fail fast mode” and Section 11.3, “Programmatic constraint declaration” to learn more about the fail fast mode and the constraint declaration API.
When working with a configured validator factory it can occasionally
be required to apply a different configuration to a single
Validator instance. Example 8.12, “Configuring a Validator via
usingContext()” shows how this can be achieved by
calling ValidatorFactory#usingContext().
Example 8.12. Configuring a Validator via
usingContext()
ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
Validator validator = validatorFactory.usingContext()
.messageInterpolator( new MyMessageInterpolator() )
.traversableResolver( new MyTraversableResolver() )
.getValidator();
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 9.1, “Example classes”.
Example 9.1. Example classes
package org.hibernate.validator.referenceguide.chapter07;
public class Person {
public interface Basic {
}
@NotNull
private String name;
//getters and setters ...
}
public interface Vehicle {
public interface Basic {
}
@NotNull(groups = Vehicle.Basic.class)
String getManufacturer();
}
@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...
}
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.
Example 9.2, “Using BeanDescriptor” demonstrates
how to retrieve a BeanDescriptor for the
Car class and how to use this descriptor in form of
assertions.
Tip
If a constraint declaration hosted by the requested class is
invalid, a ValidationException is
thrown.
Example 9.2. Using BeanDescriptor
Validator validator = Validation.buildDefaultValidatorFactory().getValidator();
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
Section 9.4, “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 Section 9.6, “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 Section 2.1.4, “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).
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. Example 9.3, “Using PropertyDescriptor” shows how to use the
PropertyDescriptor interface.
Example 9.3. Using 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 Section 9.5, “GroupConversionDescriptor” for more details on
GroupConversionDescriptor.
Constrained methods and constructors are represented by the
interfaces MethodDescriptor
and ConstructorDescriptor,
respectively. Example 9.4, “Using MethodDescriptor and
ConstructorDescriptor”
demonstrates how to work with these descriptors.
Example 9.4. Using 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 Section 8.2.4, “ParameterNameProvider”) via
getName() and
getIndex().
Tip
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 PropertyDescriptor (e.g.
BeanDescriptor.getConstraintsForProperty("foo")) or by
examining the return value descriptor of the getter's
MethodDescriptor (e.g.
BeanDescriptor.getConstraintsForMethod("getFoo").getReturnValueDescriptor()).
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
PropertyDescriptororParameterDescriptorrespectively,Object[].classwhen invoked onCrossParameterDescriptor,the return type when invoked on
ConstructorDescriptor,MethodDescriptororReturnValueDescriptor.void.classwill be returned for methods which don't have a return value.
Example 9.5, “Using ElementDescriptor methods” shows how these methods are used.
Example 9.5. Using 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. Example 9.6, “Usage of ConstraintFinder” shows how to retrieve a
ConstraintFinder instance via
findConstraints() and use the API to query for
constraint metadata.
Example 9.6. Usage of 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.
Warning
Order is not respected by
unorderedAndMatchingGroups(), but group
inheritance and inheritance via sequence are.
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. Example 9.7, “Using GroupConversionDescriptor” shows an
example.
Example 9.7. Using 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() );
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.
Example 9.8, “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.
Example 9.8. Using 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()
);
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.
Hibernate Validator integrates with both Hibernate and all pure Java Persistence providers.
Tip
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.
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 Table 2.2, “Bean Validation constraints” and Table 2.3, “Custom 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.
Hibernate Validator has a built-in Hibernate event listener -
org.hibernate.cfg.beanvalidation.BeanValidationEventListener
- which is part of Hibernate Annotations (as of Hibernate 3.5.x).
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. Example 10.1, “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 ConstraintViolations describing each
failure.
If Hibernate Validator is present in the classpath, Hibernate
Annotations (or Hibernate EntityManager) will use it transparently. To
avoid validation even though Hibernate Validator is in the classpath set
javax.persistence.validation.mode to
none.
Note
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
Core, use the following configuration in
hibernate.cfg.xml:
Example 10.1. Manual configuration of
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>
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 Section 10.1.2, “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 Section 10.1.2, “Hibernate event-based validation” to your
project and register it manually.
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.
Example 10.2, “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 seperated list of validation
groups. The default is
javax.validation.groups.Default. For more
information refer to the Seam documentation or the JSF 2
specification.
Example 10.2. Usage of Bean Validation within JSF2
<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>
Tip
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
MessageInterpolator to ensure ensure proper
localization. To encourage the use of the Bean Validation message
facility, JSF 2 will per default only display the generated Bean
Validation message. This can, however, be configured via the application
resource bundle by providing the following configuration
({0} is replaced with the Bean Validation message
and {1} is replaced with the JSF component
label):
javax.faces.validator.BeanValidator.MESSAGE={1}: {0}The default is:
javax.faces.validator.BeanValidator.MESSAGE={0}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 Jave 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 Section 1.1.2, “CDI”.
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 Example 10.3, “Retrieving validator factory and validator via
@Inject”.
Example 10.3. Retrieving validator factory and validator via
@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 Chapter 7, 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 Example 10.4, “Using the @HibernateValidator qualifier annotation”.
Example 10.4. Using the @HibernateValidator qualifier annotation
package org.hibernate.validator.referenceguide.chapter10.cdi.validator.qualifier;
@ApplicationScoped
public class RentalStation {
@Inject
@HibernateValidator
private ValidatorFactory validatorFactory;
@Inject
@HibernateValidator
private Validator validator;
//...
}
Tip
The fully-qualified name of the qualifier annotation is
org.hibernate.validator.cdi.HibernateValidator.
Be sure to not import
org.hibernate.validator.HibernateValidator
instead which is the ValidationProvider
implementation used for selecting Hibernate Validator when working
with the bootstrapping API (see Section 8.1, “Retrieving ValidatorFactory and
Validator”).
Via @Inject you also can inject
dependencies into constraint validators and other Bean Validation
objects such as MessageInterpolator
implementations etc.
Example 10.5, “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.
Example 10.5. Constraint validator with injected bean
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 );
}
}
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.
You can see an example in Example 10.6, “CDI managed beans with method-level constraints”.
Example 10.6. 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) {
//...
}
@NotNull
List<Car> getAvailableCars() {
//...
}
}
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.
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 Example 10.6, “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 Section 7.1, “Configuring the validator factory in validation.xml” for an exampleUse the
@ValidateOnExecutionannotation 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
Example 10.7, “Using @ValidateOnExecution” shows how to
use the @ValidateOnExecution annotation:
Example 10.7. Using @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) {
//...
}
@NotNull
public List<Car> getAvailableCars() {
//...
}
}
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.
Tip
Executable validation can be turned off globally by specifying
<executable-validation enabled="false"/> in
META-INF/validation.xml. In this case, any
@ValidateOnExecution annotations are
ignored.
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 Example 10.8, “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.
Example 10.8. Using 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);
}
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) {
//...
}
}
When your application runs on a Java EE application server such as
WildFly, you also can obtain Validator and
ValidatorFactory instances via
@Resource injection in managed objects such as EJBs
etc., as shown in Example 10.9, “Retrieving Validator and
ValidatorFactory via
@Resource injection”.
Example 10.9. Retrieving Validator and
ValidatorFactory via
@Resource injection
package org.hibernate.validator.referenceguide.chapter10.javaee;
@Stateless
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 Chapter 7, 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.
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.
Note
Using the features described in the following sections may result in application code which is not portable between Bean Validation providers.
Let's start, however, with a look at the public API of Hibernate Validator. Table 11.1, “Hibernate Validator public API” lists all packages belonging to this API and describes their purpose. Note that when a package is part of the public this is not necessarily true for its sub-packages.
Table 11.1. Hibernate Validator public API
| Packages | Description |
|---|---|
| org.hibernate.validator | Classes used by the Bean Validation bootstrap mechanism (eg. validation provider, configuration class); For more details see Chapter 8, Bootstrapping. |
| org.hibernate.validator.cfg, org.hibernate.validator.cfg.context, org.hibernate.validator.cfg.defs | Hibernate Validator's fluent API for constraint
declaration; In org.hibernate.validator.cfg you
will find the ConstraintMapping interface
and in org.hibernate.validator.cfg.defs all
constraint definitions. Refer to Section 11.3, “Programmatic constraint declaration” for the details. |
| org.hibernate.validator.constraints, org.hibernate.validator.constraints.br | 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 Section 2.3.2, “Additional constraints”. |
| org.hibernate.validator.constraintvalidation | Extended constraint validator context which allows to set custom attributes for message interpolation. Section 11.6.1, “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 Section 5.3, “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 the
ResourceBundleLocator SPI for the loading of resource
bundles (see Section 4.2.1, “ResourceBundleLocator”)
and its default implementation. |
| org.hibernate.validator.parameternameprovider | A ParameterNameProvider based on the
ParaNamer library, see Section 11.7, “ParaNamer based
ParameterNameProvider”. |
| org.hibernate.validator.valuehandling, org.hibernate.validator.spi.valuehandling | Classes related to the processing of values prior to their validation, see Section 11.8, “Unwrapping values prior to validation”. |
Note
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. ResourceBundleLocator).
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.
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.
Example 11.1, “Using the fail fast validation mode” shows how to bootstrap and use a fail fast enabled validator.
Example 11.1. Using the fail fast validation mode
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.
Note
There is no guarantee in which order the constraints are
evaluated, i.e. it is not deterministic whether the returned violation
originates from the @NotNull or the
@AssertTrue constraint. If required, a
deterministic evaluation order can be enforced using group sequences as
described in Section 5.2, “Defining group sequences”.
Refer to Section 8.2.6, “Provider-specific settings” to learn about the different ways of enabling the fail fast mode when bootstrapping a validator.
As per the Bean Validation specification, you can 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 Example 11.2, “Programmatic constraint declaration”.
Example 11.2. 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.
Note
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 ValidationException is
raised.
Note
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 Example 11.3, “Programmatic declaration of a custom constraint”.
Example 11.3. 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 Example 11.4, “Marking a property for cascaded validation”.
Example 11.4. 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 Example 11.5, “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.
Example 11.5. Programmatic declaration of method and constructor 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.
Example 11.6. Configuration of default group sequence and default group sequence provider
ConstraintMapping constraintMapping = configuration.createConstraintMapping();
constraintMapping
.type( Car.class )
.defaultGroupSequence( Car.class, CarChecks.class )
.type( RentalCar.class )
.defaultGroupSequenceProviderClass( RentalCarGroupSequenceProvider.class );
Bean Validation specifies that the constraints of a composed
constraint (see Section 6.4, “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.
Example 11.7, “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.
Example 11.7. OR composition of constraints
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 { };
}
Tip
Using ALL_FALSE as composition type implicitly enforces that only a single violation will get reported in case validation of the constraint composition fails.
As described in Section 4.2, “Custom message interpolation”, Bean Validation allows to plug in custom message interpolator implementations.
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 Section 4.2.1, “ResourceBundleLocator” to learn how to make use of
that SPI.
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.
HibernateConstraintValidatorContext
is a subtype of ConstraintValidatorContext which
allows you to set arbitrary parameters for interpolation via the
Expression Language message interpolation facility (see Section 4.1.2, “Interpolation with message expressions”). For example
the default error message for the @Future
constraint is "must be in the future". What if you would like to include
the current date to make the message more explicit? Example 11.8, “Custom @Future validator with message
parameters” shows how this could be
achieved.
Example 11.8. Custom @Future validator with message
parameters
public class MyFutureValidator implements ConstraintValidator<Future, Date> {
public void initialize(Future constraintAnnotation) {
}
public boolean isValid(Date value, ConstraintValidatorContext context) {
Date now = GregorianCalendar.getInstance().getTime();
if ( value.before( now ) ) {
HibernateConstraintValidatorContext hibernateContext =
context.unwrap( HibernateConstraintValidatorContext.class );
hibernateContext.disableDefaultConstraintViolation();
hibernateContext.addExpressionVariable( "now", now )
.buildConstraintViolationWithTemplate( "Must be after ${now}" )
.addConstraintViolation();
return false;
}
return true;
}
}
Note
Note that the parameters specified via
addExpressionVariable(String, Object) are
global and apply for all constraint violations created by this
isValid() invocation. This includes the
default constraint violation, but also all violations created by the
ConstraintViolationBuilder. You can, however,
update the parameters between invocations of
ConstraintViolationBuilder#addConstraintViolation().
Warning
This functionality is currently experimental and might change in future versions.
Hibernate Validator also offers a custom extension of
MessageInterpolatorContext, namely
HibernateMessageInterpolatorContext (see Example 11.9, “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.
Example 11.9. HibernateMessageInterpolatorContext
public interface HibernateMessageInterpolatorContext extends MessageInterpolator.Context {
/**
* Returns the currently validated root bean type.
*
* @return The currently validated root bean type.
*/
Class<?> getRootBeanType();
}
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 Example 8.8, “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.
Tip
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
com.thoughtworks.paranamer and the artifact id
paranamer.
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.
Sometimes it is required to unwrap values prior to the validation. E.g. in Example 11.10, “Using@UnwrapValidatedValue” property types as specified by JavaFX are used to define an element of some domain model.
Example 11.10. Using@UnwrapValidatedValue
@Size(min = 3)
@UnwrapValidatedValue
private Property<String> name = new SimpleStringProperty( "Bob" );
Note
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.
In JavaFX, bean properties 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.
To do so, put the @UnwrapValidatedValue
annotation to the element in question. This will advice the validation
engine to look for an unwrapper implementation which returns the data type
to be used for constraint validator resolution and unwraps the validated
value. Unwrapper types must extend the SPI class
ValidatedValueUnwrapper as shown in
Example 11.11, “Implementing the ValidatedValueUnwrapper
interface”.
Example 11.11. Implementing the ValidatedValueUnwrapper
interface
public class PropertyValueUnwrapper extends ValidatedValueUnwrapper<Property<?>> {
@Override
public Object handleValidatedValue(Property<?> value) {
//...
}
@Override
public Type getValidatedValueType(Type valueType) {
//...
}
}
Value unwrappers must be registered when obtaining a Validator
instance as follows:
Example 11.12. Registering a ValidatedValueUnwrapper
Validator validator = Validation.byProvider( HibernateValidator.class )
.configure()
.addValidatedValueHandler( new PropertyValueUnwrapper() )
.buildValidatorFactory()
.getValidator();
Several unwrapper implementations can be registered when working with different kinds of wrapper types in one application. 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.
Alternatively, 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 Chapter 7, Configuring via XML).
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.
Tip
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 org.hibernate:hibernate-validator-annotation-processor:5.1.3.Final.
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.
As of Hibernate Validator 5.1.3.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
@Validonly 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
@GroupSequenceProvideris valid
The behavior of the Hibernate Validator Annotation Processor can be controlled using the processor options listed in table Table 12.1, “Hibernate Validator Annotation Processor options”:
Table 12.1. Hibernate Validator Annotation Processor options
| Option | Explanation |
|---|---|
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 of
ERROR will cause compilation to halt
whenever the AP detects a constraint problem. Defaults to
ERROR. |
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 to false to allow constraints only at
JavaBeans getter methods as defined by the Bean Validation API.
Defaults to true. |
verbose | Controls whether detailed processing information shall be
displayed or not, useful for debugging purposes. Must be either
true or false. Defaults to
false. |
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).
When compiling on the command line using javac, specify the JAR hibernate-validator-annotation-processor-5.1.3.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.
Example 12.1. Using the annotation processor with javac
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-5.1.3.Final.jar
Similar to directly working with javac, the annotation processor can be added as as compiler argument when invoking the javac task for Apache Ant:
Example 12.2. Using the annotation processor with 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-5.1.3.Final.jar"/>
</javac>
There are several options for integrating the annotation processor with Apache Maven. Generally it is sufficient to add the Hibernate Validator Annotation Processor as dependency to your project:
Example 12.3. Adding the HV Annotation Processor as dependency
...
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
<version>5.1.3.Final</version>
</dependency>
...
The processor will then be executed automatically by the compiler. This basically works, but comes with the disadavantage that in some cases messages from the annotation processor are not displayed (see MCOMPILER-66).
Another option is using the Maven Annotation Plugin. To work with this plugin, disable the standard annotation processing performed by the compiler plugin and configure the annotation plugin by specifying an execution and adding the Hibernate Validator Annotation Processor as plugin dependency (that way the processor is not visible on the project's actual classpath):
Example 12.4. Configuring the Maven Annotation Plugin
...
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
<compilerArgument>-proc:none</compilerArgument>
</configuration>
</plugin>
<plugin>
<groupId>org.bsc.maven</groupId>
<artifactId>maven-processor-plugin</artifactId>
<version>2.2.1</version>
<executions>
<execution>
<id>process</id>
<goals>
<goal>process</goal>
</goals>
<phase>process-sources</phase>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
<version>5.1.3.Final</version>
</dependency>
</dependencies>
</plugin>
...
Do the following to use the annotation processor within the Eclipse IDE:
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-5.1.3.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:
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-5.1.3.Final.jar
Add the processor's fully qualified name
org.hibernate.validator.ap.ConstraintValidationProcessorto the "Annotation Processors" listIf applicable add you module to the "Processed Modules" list
Rebuilding your project then should show any erronous constraint annotations:
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-5.1.3.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:
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.
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!