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 >= 5
Apache Maven
An Internet connection (Maven has to download all required libraries)

A properly configured remote repository. Add the following to your settings.xml:

Example 1.1. Configuring the JBoss Maven repository in settings.xml

<repositories>
    <repository>
        <id>jboss</id>
        <url>http://repository.jboss.com/maven2</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>

More information about settings.xml can be found in the Maven Local Settings Model.

Note

Hibernate Validator uses JAXB for XML parsing. JAXB is part of the Java Class Library since Java 6 which means that if you run Hibernate Validator with Java 5 you will have to add additional JAXB dependencies. Using maven you have to add the following dependencies:

<dependency>
    <groupId>javax.xml.bind</groupId>
    <artifactId>jaxb-api</artifactId>
    <version>2.2</version>
</dependency>
<dependency>
    <groupId>com.sun.xml.bind</groupId>
    <artifactId>jaxb-impl</artifactId>
    <version>2.1.12</version>
</dependency>

if you are using the SourceForge package you find the necessary libraries in the lib/jdk5 directory. In case you are not using the XML configuration you can also disable it explicitly by calling Configuration.ignoreXmlConfiguration() during ValidationFactory creation. In this case the JAXB dependencies are not needed.

1.1. Setting up a new Maven project

Start by creating new Maven project using the Maven archetype plugin as follows:

Example 1.2. Using Maven's archetype plugin to create a sample project using Hibernate Validator

mvn archetype:create -DarchetypeGroupId=org.hibernate \
                     -DarchetypeArtifactId=hibernate-validator-quickstart-archetype \
                     -DarchetypeVersion=4.1.0.Final \
                     -DgroupId=com.mycompany 
                     -DartifactId=hv-quickstart

Maven will create your project in the directory hv-quickstart. Change into this directory and run:

mvn test

Maven will compile the example code and run the implemented unit tests. Let's have a look at the actual code.

1.2. Applying constraints

Open the project in the IDE of your choice and have a look at the class Car:

Example 1.3. Class Car annotated with constraints

package com.mycompany;


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 ...

}

@NotNull, @Size and @Min are so-called constraint annotations, that we use to declare constraints, which shall be applied to the fields of a Car instance:

manufacturer shall never be null
licensePlate shall never be null and must be between 2 and 14 characters long
seatCount shall be at least 2.

1.3. Validating constraints

To perform a validation of these constraints, we use a Validator instance. Let's have a look at the CarTest class:

Example 1.4. Class CarTest showing validation examples

package com.mycompany;


import static org.junit.Assert.*;


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;


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 we get a Validator instance from the ValidatorFactory. A Validator instance is thread-safe and may be reused multiple times. For this reason we store it as field of our test class. We can use the Validator now to validate the different car instances in the test methods.

The validate() method returns a set of ConstraintViolation instances, which we can iterate in order to see which validation errors occurred. The first three test methods show some expected constraint violations:

The @NotNull constraint on manufacturer is violated in manufacturerIsNull()
The @Size constraint on licensePlate is violated in licensePlateTooShort()
The @Min constraint on seatCount is violated in seatCountTooLow()

If the object validates successfully, validate() returns an empty set.

Note that we only use classes from the package javax.validation from the Bean Validation API. As we don't reference any classes of the RI directly, it would be no problem to switch to another implementation of the API, should that need arise.

1.4. Where to go next?

That concludes our 5 minute tour through the world of Hibernate Validator. Continue exploring the code examples or look at further examples referenced in Chapter 9, Further reading. To deepen your understanding of Hibernate Validator just continue reading Chapter 2, Validation step by step. In case your application has specific validation requirements have a look at Chapter 3, Creating custom constraints.

Chapter 2. Validation step by step

2.1. Defining constraints

2.1.1. Field-level constraints
2.1.2. Property-level constraints
2.1.3. Class-level constraints
2.1.4. Constraint inheritance
2.1.5. Object graphs

2.2. Validating constraints

2.2.1. Obtaining a Validator instance
2.2.2. Validator methods
2.2.3. ConstraintViolation methods
2.2.4. Message interpolation

2.3. Validating groups

2.3.1. Group sequences
2.3.2. Redefining the default group sequence of a class

2.4. Built-in constraints

In this chapter we will see in more detail how to use Hibernate Validator to validate constraints for a given entity model. We will also learn which default constraints the Bean Validation specification provides and which additional constraints are only provided by Hibernate Validator. Let's start with how to add constraints to an entity.

2.1. Defining constraints

Constraints in Bean Validation are expressed via Java annotations. In this section we show how to annotate an object model with these annotations. We have to differentiate between three different type of constraint annotations - field-, property-, and class-level annotations.

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 3, Creating custom constraints for more information.

2.1.1. Field-level constraints

Constraints can be expressed by annotating a field of a class. Example 2.1, “Field level constraint” shows a field level configuration example:

Example 2.1. Field level constraint

package com.mycompany;


import javax.validation.constraints.NotNull;


public class Car {


    @NotNull

    private String manufacturer;


    @AssertTrue

    private boolean isRegistered;


    public Car(String manufacturer, boolean isRegistered) {

        super();

        this.manufacturer = manufacturer;

        this.isRegistered = isRegistered;

    }

}

When using field level constraints field access strategy is used to access the value to be validated. This means the bean validation provider directly accesses the instance variable and does not invoke the property accessor method also if such a method exists.

Note

The access type (private, protected or public) does not matter.

Note

Static fields and properties cannot be validated.

2.1.2. Property-level constraints

If your model class adheres to the JavaBeans standard, it is also possible to annotate the properties of a bean class instead of its fields. Example 2.2, “Property level constraint” uses the same entity as in Example 2.1, “Field level constraint”, however, property level constraints are used.

Note

The property's getter method has to be annotated, not its setter.

Example 2.2. Property level constraint

package com.mycompany;


import javax.validation.constraints.AssertTrue;

import javax.validation.constraints.NotNull;


public class Car {


    private String manufacturer;


    private boolean isRegistered;

      

    public Car(String manufacturer, boolean isRegistered) {

        super();

        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;

    }

}

When using property level constraints property access strategy is used to access the value to be validated. This means the bean validation provider accesses the state via the property accessor method.

Tip

It is recommended to stick either to field or property annotation within one class. It is not recommended to annotate a field and the accompanying getter method as this would cause the field to be validated twice.

2.1.3. Class-level constraints

Last but not least, a constraint can also be placed on class level. When a constraint annotation is placed on this level the class instance itself passed to the ConstraintValidator. Class level constraints are useful if it is necessary to inspect more than a single property of the class to validate it or if a correlation between different state variables has to be evaluated. In Example 2.3, “Class level constraint” we add the property passengers to the class Car. We also add the constraint PassengerCount on the class level. We will later see how we can actually create this custom constraint (see Chapter 3, Creating custom constraints). For now we it is enough to know that PassengerCount will ensure that there cannot be more passengers in a car than there are seats.

Example 2.3. Class level constraint

package com.mycompany;


import javax.validation.constraints.Min;

import javax.validation.constraints.NotNull;

import javax.validation.constraints.Size;


@PassengerCount

public class Car {


    @NotNull

    private String manufacturer;


    @NotNull

    @Size(min = 2, max = 14)

    private String licensePlate;


    @Min(2)

    private int seatCount;

    

    private List<Person> passengers;

    

    public Car(String manufacturer, String licencePlate, int seatCount) {

        this.manufacturer = manufacturer;

        this.licensePlate = licencePlate;

        this.seatCount = seatCount;

    }


    //getters and setters ...

}

2.1.4. Constraint inheritance

When validating an object that implements an interface or extends another class, all constraint annotations on the implemented interface and parent class apply in the same manner as the constraints specified on the validated object itself. To make things clearer let's have a look at the following example:

Example 2.4. Constraint inheritance using RentalCar

package com.mycompany;


import javax.validation.constraints.NotNull;


public class RentalCar extends Car {


    private String rentalStation;

    

    public RentalCar(String manufacturer, String rentalStation) {

        super(manufacturer);

        this.rentalStation = rentalStation;

    }

    

    @NotNull

    public String getRentalStation() {

        return rentalStation;

    }


    public void setRentalStation(String rentalStation) {

        this.rentalStation = rentalStation;

    }

}

Our well-known class Car is now extended by RentalCar with the additional property rentalStation. If an instance of RentalCar is validated, not only the @NotNull constraint on rentalStation is validated, but also the constraint on manufacturer from the parent class.

The same would hold true, if Car were an interface implemented by RentalCar.

Constraint annotations are aggregated if methods are overridden. If RentalCar would override the getManufacturer() method from Car any constraints annotated at the overriding method would be evaluated in addition to the @NotNull constraint from the super-class.

2.1.5. Object graphs

The Bean Validation API does not only allow to validate single class instances but also complete object graphs. To do so, just annotate a field or property representing a reference to another object with @Valid. If the parent object is validated, all referenced objects annotated with @Valid will be validated as well (as will be their children etc.). See Example 2.6, “Adding a driver to the car”.

Example 2.5. Class Person

package com.mycompany;


import javax.validation.constraints.NotNull;


public class Person {


    @NotNull

    private String name;

    

    public Person(String name) {

        super();

        this.name = name;

    }


    public String getName() {

        return name;

    }


    public void setName(String name) {

        this.name = name;

    }

}

Example 2.6. Adding a driver to the car

package com.mycompany;


import javax.validation.Valid;

import javax.validation.constraints.NotNull;


public class Car {


    @NotNull

    @Valid

    private Person driver;

    

    public Car(Person driver) {

        this.driver = driver;

    }


    //getters and setters ...

}

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.

Object graph validation also works for collection-typed fields. That means any attributes that

are arrays
implement java.lang.Iterable (especially Collection, List and Set)
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 2.7. Car with a list of passengers

package com.mycompany;


import java.util.ArrayList;

import java.util.List;


import javax.validation.Valid;

import javax.validation.constraints.NotNull;


public class Car {


    @NotNull

    @Valid

    private List<Person> passengers = new ArrayList<Person>();


    public Car(List<Person> passengers) {

        this.passengers = passengers;

    }


    //getters and setters ...

}

If a Car instance is validated, a ConstraintValidation will be created, if any of the Person objects contained in the passengers list has a null name.

Note

null values are getting ignored when validating object graphs.

2.2. Validating constraints

The Validator interface is the main entry point to Bean Validation. In Section 5.1, “Configuration and ValidatorFactory” we will first show how to obtain an Validator instance. Afterwards we will learn how to use the different methods of the Validator interface.

2.2.1. Obtaining a `Validator` instance

The first step towards validating an entity instance is to get hold of a Validator instance. The road to this instance leads via the Validation class and a ValidatorFactory. The easiest way is to use the static Validation.buildDefaultValidatorFactory() method:

Example 2.8. Validation.buildDefaultValidatorFactory()

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

Validator validator = factory.getValidator();

For other ways of obtaining a Validator instance see Chapter 5, Bootstrapping. For now we just want to see how we can use the Validator instance to validate entity instances.

2.2.2. Validator methods

The Validator interface contains three methods that can be used to either validate entire entities or just a 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) will be used. We will go into more detail on the topic of validation groups in Section 2.3, “Validating groups”

2.2.2.1. `validate`

Use the validate() method to perform validation of all constraints of a given entity instance (see Example 2.9, “Usage of Validator.validate()” ).

Example 2.9. Usage of Validator.validate()

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

Validator validator = factory.getValidator();


Car car = new Car(null);


Set<ConstraintViolation<Car>> constraintViolations = validator.validate(car);


assertEquals(1, constraintViolations.size());

assertEquals("may not be null", constraintViolations.iterator().next().getMessage());

2.2.2.2. `validateProperty`

With help of the validateProperty() a single named property of a given object can be validated. The property name is the JavaBeans property name.

Example 2.10. Usage of Validator.validateProperty()

Validator validator = Validation.buildDefaultValidatorFactory().getValidator();


Car car = new Car(null);


Set<ConstraintViolation<Car>> constraintViolations = validator.validateProperty(car, "manufacturer");


assertEquals(1, constraintViolations.size());

assertEquals("may not be null", constraintViolations.iterator().next().getMessage());

Validator.validateProperty is for example used in the integration of Bean Validation into JSF 2 (see Section 6.4, “Presentation layer validation”).

2.2.2.3. `validateValue`

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 2.11. Usage of Validator.validateValue()

Validator validator = Validation.buildDefaultValidatorFactory().getValidator();


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().

2.2.3. `ConstraintViolation` methods

Now it is time to have a closer look at what a ConstraintViolation. 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:

Table 2.1. The various ConstraintViolation methods

Method	Usage	Example (referring to Example 2.9, “Usage of Validator.validate()”)
`getMessage()`	The interpolated error message.	may not be null
`getMessageTemplate()`	The non-interpolated error message.	{javax.validation.constraints.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 value from root bean.
`getInvalidValue()`	The value failing to pass the constraint.	passengers
`getConstraintDescriptor()`	Constraint metadata reported to fail.

2.2.4. Message interpolation

As we will see in Chapter 3, Creating custom constraints each constraint definition must define a default message descriptor. This message can be overridden at declaration time using the message attribute of the constraint. You can see this in Example 2.13, “Driver”. This message descriptors get interpolated when a constraint validation fails using the configured MessageInterpolator. The interpolator will try to resolve any message parameters, meaning string literals enclosed in braces. In order to resolve these parameters Hibernate Validator's default MessageInterpolator first recursively resolves parameters against a custom ResourceBundle called ValidationMessages.properties at the root of the classpath (It is up to you to create this file). If no further replacements are possible against the custom bundle the default ResourceBundle under /org/hibernate/validator/ValidationMessages.properties gets evaluated. If a replacement occurs against the default bundle the algorithm looks again at the custom bundle (and so on). Once no further replacements against these two resource bundles are possible remaining parameters are getting resolved against the attributes of the constraint to be validated.

Since the braces { and } have special meaning in the messages they need to be escaped if they are used literally. The following The following rules apply:

\{ is considered as the literal {
\} is considered as the literal }
\\ is considered as the literal \

If the default message interpolator does not fit your requirements it is possible to plug a custom MessageInterpolator when the ValidatorFactory gets created. This can be seen in Chapter 5, Bootstrapping.

2.3. Validating groups

Groups allow you to restrict the set of constraints applied during validation. This makes for example wizard like validation possible where in each step only a specified subset of constraints get validated. The groups targeted are passed as var-args parameters to validate, validateProperty and validateValue. Let's have a look at an extended Car with Driver example. First we have the class Person (Example 2.12, “Person”) which has a @NotNullconstraint on name. Since no group is specified for this annotation its default group is javax.validation.groups.Default.

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 2.12. Person

public class Person {

    @NotNull

    private String name;


    public Person(String name) {

        this.name = name;

    }

    // getters and setters ...

}

Next we have the class Driver (Example 2.13, “Driver”) extending Person. Here we are adding the properties age and hasDrivingLicense. In order to drive you must be at least 18 (@Min(18)) and you must have a driving license (@AssertTrue). Both constraints defined on these properties belong to the group DriverChecks. As you can see in Example 2.14, “Group interfaces” the group DriverChecks is just a simple tagging interface. Using interfaces makes the usage of groups type safe and allows for easy refactoring. It also means that groups can inherit from each other via class inheritance.

Note

The Bean Validation specification does not enforce that groups have to be interfaces. Non interface classes could be used as well, but we recommend to stick to interfaces.

Example 2.13. Driver

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;

    }

}

Example 2.14. Group interfaces

public interface DriverChecks {

}


public interface CarChecks {

}

Last but not least we add the property passedVehicleInspection to the Car class (Example 2.15, “Car”) indicating whether a car passed the road worthy tests.

Example 2.15. Car

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;

    }

}

Overall three different groups are used in our example. Person.name, Car.manufacturer, Car.licensePlate and Car.seatCount all belong to the Default group. Driver.age and Driver.hasDrivingLicense belong to DriverChecks and last but not least Car.passedVehicleInspection belongs to the group CarChecks. Example 2.16, “Drive away” shows how passing different group combinations to the Validator.validate method result in different validation results.

Example 2.16. Drive away

public class GroupTest {


    private static Validator validator;


    @BeforeClass

    public static void setUp() {

        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

        validator = factory.getValidator();

    }


    @Test

    public void driveAway() {

        // 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() );

    }

}

First we create a car and validate it 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. Next we just validate the CarChecks group which will fail until we make sure that the car passes the vehicle inspection. When we then add a driver to the car and validate against DriverChecks we get again a 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 will pass.

Last but not least, we show that all constraints are passing by validating against all defined groups.

2.3.1. Group sequences

By default, constraints are evaluated in no particular order and this regardless of which groups they belong to. In some situations, however, it is useful to control the order of the constraints evaluation. In our example from Section 2.3, “Validating groups” we could for example require that first all default car constraints are passing before we check the road worthiness of the car. Finally before we drive away we check the actual driver constraints. In order to implement such an order one would define a new interface and annotate it with @GroupSequence defining the order in which the groups have to be validated.

Note

If at least one constraints fails in a sequenced group none of the constraints of the following groups in the sequence get validated.

Example 2.17. Interface with @GroupSequence

@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.

The usage of the new sequence could then look like in Example 2.18, “Usage of a group sequence”.

Example 2.18. Usage of a group sequence

@Test

public void testOrderedChecks() {

    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() );

}

2.3.2. Redefining the default group sequence of a class

The @GroupSequence annotation also fulfills a second purpose. It allows you to redefine what the Default group means for a given class. To redefine Default for a class, place a @GroupSequence annotation on the class. The defined groups in the annotation express the sequence of groups that substitute Default for this class. Example 2.19, “RentalCar” introduces a new class RentalCar with a redfined default group. With this definition the check for all three groups can be rewritten as seen in Example 2.20, “testOrderedChecksWithRedefinedDefault”.

Example 2.19. RentalCar

@GroupSequence({ RentalCar.class, CarChecks.class })

public class RentalCar extends Car {

    public RentalCar(String manufacturer, String licencePlate, int seatCount) {

        super( manufacturer, licencePlate, seatCount );

    }

}

Example 2.20. testOrderedChecksWithRedefinedDefault

@Test

public void testOrderedChecksWithRedefinedDefault() {

    RentalCar rentalCar = new RentalCar( "Morris", "DD-AB-123", 2 );

    rentalCar.setPassedVehicleInspection( true );


    Driver john = new Driver( "John Doe" );

    john.setAge( 18 );

    john.passedDrivingTest( true );

    rentalCar.setDriver( john );


    assertEquals( 0, validator.validate( rentalCar, Default.class, DriverChecks.class ).size() );

}

Note

Due to the fact that there cannot be a 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 should be added!

2.4. Built-in constraints

Hibernate Validator implements all of the default constraints specified in Bean Validation as well as some custom ones. Table 2.2, “Built-in constraints” list all constraints available in Hibernate Validator.

Table 2.2. Built-in constraints

Annotation	Part of Bean Validation Specification	Apply on	Use	Hibernate Metadata impact
@AssertFalse	yes	field/property	Check that the annotated element is `false`.	none
@AssertTrue	yes	field/property	Check that the annotated element is `true`.	none
@CreditCardNumber	no	field/property. The supported type is `String`.	Check that the annotated string passes the Luhn checksum test. Note, this validation aims to check for user mistake, not credit card validity! See also Anatomy of Credit Card Numbers.	none
@DecimalMax	yes	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	The annotated element must be a number whose value must be lower 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	yes	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	The annotated element must be a number whose value must be higher 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=)	yes	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	Check whether the property is a number having up to `integer` digits and `fraction` fractional digits.	Define column precision and scale.
@Email	no	field/property. Needs to be a string.	Check whether the specified string is a valid email address.	none
@Future	yes	field/property. Supported types are `java.util.Date` and `java.util.Calendar`.	Checks whether the annotated date is in the future.	none
@Length(min=, max=)	no	field/property. Needs to be a string.	Validate that the annotated string is between `min` and `max` included.	Column length will be set to max.
@Max	yes	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	Checks whether the annotated value is less than or equal to the specified maximum.	Add a check constraint on the column.
@Min	yes	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	Checks whether the annotated value is higher than or equal to the specified minimum.	Add a check constraint on the column.
@NotNull	yes	field/property	Check that the annotated value is not `null.`	Column(s) are not null.
@NotBlank	no	field/property	Check that the annotated string 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	no	field/property. Supported types are String, Collection, Map and arrays.	Check whether the annotated element is not `null` nor empty.	none
@Null	yes	field/property	Check that the annotated value is `null.`	none
@Past	yes	field/property. Supported types are `java.util.Date` and `java.util.Calendar`.	Checks whether the annotated date is in the past.	none
@Pattern(regex=, flag=)	yes	field/property. Needs to be a string.	Checks if the annotated string matches the regular expression `regex` considering the given flag `match`.	none
@Range(min=, max=)	no	field/property. Supported types are `BigDecimal`, `BigInteger`, `String`, `byte`, `short`, `int`, `long` and the respective wrappers of the primitive types.	Check whether the annotated value lies between (inclusive) the specified minimum and maximum.	none
@Size(min=, max=)	yes	field/property. Supported types are `String`, `Collection`, `Map` and `arrays`.	Check if the annotated element size is between min and max (inclusive).	Column length will be set to max.
@ScriptAssert(lang=, script=, alias=)	no	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 Java^TM Platform") must part of the class path. This is automatically the case when running on Java 6. For older Java versions, the JSR 223 RI can be added manually to 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=)	no	field/property. The supported type is `String`.	Check if the annotated string is a valid URL. If any of parameters `protocol`, `host` or `port` is specified the URL must match the specified values in the according part.	none
@Valid	yes	field/property. Any non-primitive types are supported.	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, “Built-in constraints” each constraint supports the parameters message, groups and payload. This is a requirement of the Bean Validation specification.

In some cases these built-in constraints will not fulfill your requirements. In this case you can literally in a minute write your own constraints. We will discuss this in Chapter 3, Creating custom constraints

Chapter 3. Creating custom constraints

3.1. Creating a simple constraint

3.1.1. The constraint annotation
3.1.2. The constraint validator
3.1.3. The error message
3.1.4. Using the constraint

3.2. Constraint composition

Though the Bean Validation API defines a whole set of standard constraint annotations one can easily think of situations in which these standard annotations won't suffice. For these cases you are able to create custom constraints tailored to your specific validation requirements in a simple manner.

3.1. Creating a simple constraint

To create a custom constraint, the following three steps are required:

Create a constraint annotation
Implement a validator
Define a default error message

3.1.1. The constraint annotation

Let's write a constraint annotation, that can be used to express that a given string shall either be upper case or lower case. We'll apply it later on to the licensePlate field of the Car class from Chapter 1, Getting started to ensure, that the field is always an upper-case string.

First we need a way to express the two case modes. We might use String constants, but a better way to go is to use a Java 5 enum for that purpose:

Example 3.1. Enum CaseMode to express upper vs. lower case

package com.mycompany;


public enum CaseMode {

    UPPER, 

    LOWER;

}

Now we can 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 3.2. Defining CheckCase constraint annotation

package com.mycompany;


import static java.lang.annotation.ElementType.*;

import static java.lang.annotation.RetentionPolicy.*;


import java.lang.annotation.Documented;

import java.lang.annotation.Retention;

import java.lang.annotation.Target;


import javax.validation.Constraint;

import javax.validation.Payload;


@Target( { METHOD, FIELD, ANNOTATION_TYPE })

@Retention(RUNTIME)

@Constraint(validatedBy = CheckCaseValidator.class)

@Documented

public @interface CheckCase {


    String message() default "{com.mycompany.constraints.checkcase}";


    Class<?>[] groups() default {};


    Class<? extends Payload>[] payload() default {};

    

    CaseMode 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 Section 2.3, “Validating groups”). This must default to an empty array of type Class<?>.
an attribute payload that can be used by clients of the Bean Validation API to assign custom payload objects to a constraint. This attribute is not used by the API itself.
Tip
An example for a custom payload could be the definition of a severity.
```
public class Severity {
    public static class Info extends Payload {};
    public static class Error extends Payload {};
}

public class ContactDetails {
    @NotNull(message="Name is mandatory", payload=Severity.Error.class)
    private String name;

    @NotNull(message="Phone number not specified, but not mandatory", payload=Severity.Info.class)
    private String phoneNumber;

    // ...
}
```
Now a client can after the validation of a ContactDetails instance access the severity of a constraint using ConstraintViolation.getConstraintDescriptor().getPayload() and adjust its behaviour depending on the severity.

Besides those three mandatory attributes (message, groups and payload) we add another one allowing for the required case mode to be specified. The name value is a special one, which can be omitted upon using the annotation, if it is the only attribute specified, as e.g. in @CheckCase(CaseMode.UPPER).

In addition we annotate the annotation type with a couple of so-called meta annotations:

@Target({ METHOD, FIELD, ANNOTATION_TYPE }): Says, that methods, fields and annotation declarations may be annotated with @CheckCase (but not type declarations e.g.)
@Retention(RUNTIME): Specifies, that annotations of this type will be available at runtime by the means of reflection
@Constraint(validatedBy = CheckCaseValidator.class): Specifies the validator to be used to validate elements annotated with @CheckCase
@Documented: Says, that the use of @CheckCase will be contained in the JavaDoc of elements annotated with it

3.1.2. The constraint validator

Next, we need to implement a constraint validator, that's able to validate elements with a @CheckCase annotation. To do so, we implement the interface ConstraintValidator as shown below:

Example 3.3. Implementing a constraint validator for the constraint CheckCase

package com.mycompany;


import javax.validation.ConstraintValidator;

import javax.validation.ConstraintValidatorContext;


public class CheckCaseValidator implements ConstraintValidator<CheckCase, String> {


    private CaseMode caseMode;


    public void initialize(CheckCase constraintAnnotation) {

        this.caseMode = constraintAnnotation.value();

    }


    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 we set in our implementation. The first one specifies the annotation type to be validated (in our example CheckCase), the second one the type of elements, which the validator can handle (here String).

In case a constraint annotation is allowed at elements of different 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 us access to the attribute values of the annotation to be validated. In the example we store the CaseMode in a field of the validator for further usage.

In the isValid() method we implement the logic, that determines, whether a String is valid according to a given @CheckCase annotation or not. This decision depends on the case mode retrieved in initialize(). As the Bean Validation specification recommends, we consider null values as being valid. If null is not a valid value for an element, it should be annotated with @NotNull explicitly.

3.1.2.1. The ConstraintValidatorContext

Example 3.3, “Implementing a constraint validator for the constraint CheckCase” relies on the default error message generation by just returning true or false from the isValid call. 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 3.4. Use of ConstraintValidatorContext to define custom error messages

package com.mycompany;


import javax.validation.ConstraintValidator;

import javax.validation.ConstraintValidatorContext;


public class CheckCaseValidator implements ConstraintValidator<CheckCase, String> {


    private CaseMode caseMode;


    public void initialize(CheckCase constraintAnnotation) {

        this.caseMode = constraintAnnotation.value();

    }


    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( "{com.mycompany.constraints.CheckCase.message}"  ).addConstraintViolation();

        }

        return result;

    }


}

Example 3.4, “Use of 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 end each new constraint violation with addConstraintViolation. Only after that the new constraint violation will be created.

In case you are implementing a ConstraintValidator a class level constraint it is also possible to adjust set the property path for the created constraint violations. This is important for the case where you validate multiple properties of the class or even traverse the object graph. A custom property path creation could look like Example 3.5, “Adding new ConstraintViolation with custom property path”.

Example 3.5. Adding new ConstraintViolation with custom property path

public boolean isValid(Group group, ConstraintValidatorContext constraintValidatorContext) {

    boolean isValid = false;

    ...


    if(!isValid) {

        constraintValidatorContext

            .buildConstraintViolationWithTemplate( "{my.custom.template}" )

            .addNode( "myProperty" ).addConstraintViolation();

    }

    return isValid;

}

3.1.3. The error message

Finally we need to specify the error message, that shall be used, in case a @CheckCase constraint is violated. To do so, we add the following to our custom ValidationMessages.properties (see also Section 2.2.4, “Message interpolation”)

Example 3.6. Defining a custom error message for the CheckCase constraint

com.mycompany.constraints.CheckCase.message=Case mode must be {value}.

If a validation error occurs, the validation runtime will use the default value, that we specified for the message attribute of the @CheckCase annotation to look up the error message in this file.

3.1.4. Using the constraint

Now that our first custom constraint is completed, we can use it in the Car class from the Chapter 1, Getting started chapter to specify that the licensePlate field shall only contain upper-case strings:

Example 3.7. Applying the CheckCase constraint

package com.mycompany;


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)

    @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 let's demonstrate in a little test that the @CheckCase constraint is properly validated:

Example 3.8. Testcase demonstrating the CheckCase validation

package com.mycompany;


import static org.junit.Assert.*;


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;


public class CarTest {


    private static Validator validator;


    @BeforeClass

    public static void setUp() {

        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

        validator = factory.getValidator();

    }


    @Test

    public void testLicensePlateNotUpperCase() {


        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());

    }


    @Test

    public void carIsValid() {


        Car car = new Car("Morris", "DD-AB-123", 4);


        Set<ConstraintViolation<Car>> constraintViolations =

            validator.validate(car);


        assertEquals(0, constraintViolations.size());

    }

}

3.2. Constraint composition

Looking at the licensePlate field of the Car class in Example 3.7, “Applying the CheckCase constraint”, we 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 we had a licensePlate field in another class, we would have to copy all constraint declarations to the other class as well, violating the DRY principle.

This problem can be tackled using compound constraints. In the following we create a new constraint annotation @ValidLicensePlate, that comprises the constraints @NotNull, @Size and @CheckCase:

Example 3.9. Creating a composing constraint ValidLicensePlate

package com.mycompany;


import static java.lang.annotation.ElementType.*;

import static java.lang.annotation.RetentionPolicy.*;


import java.lang.annotation.Documented;

import java.lang.annotation.Retention;

import java.lang.annotation.Target;


import javax.validation.Constraint;

import javax.validation.Payload;

import javax.validation.constraints.NotNull;

import javax.validation.constraints.Size;


@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 "{com.mycompany.constraints.validlicenseplate}";


    Class<?>[] groups() default {};


    Class<? extends Payload>[] payload() default {};


}

To do so, we just have to annotate the constraint declaration with its comprising constraints (btw. that's exactly why we allowed annotation types as target for the @CheckCase annotation). As no additional validation is required for the @ValidLicensePlate annotation itself, we don't declare a validator within the @Constraint meta annotation.

Using the new compound constraint at the licensePlate field now is fully equivalent to the previous version, where we declared the three constraints directly at the field itself:

Example 3.10. Application of composing constraint ValidLicensePlate

package com.mycompany;


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 3.11. Usage of @ReportAsSingleViolation

//...

@ReportAsSingleViolation

public @interface ValidLicensePlate {


    String message() default "{com.mycompany.constraints.validlicenseplate}";


    Class<?>[] groups() default {};


    Class<? extends Payload>[] payload() default {};


}

4.1. `validation.xml`

The key to enable XML configuration for Hibernate Validator is the file validation.xml. If this file exists in the classpath its configuration will be applied when the ValidationFactory gets created. Example 4.1, “validation-configuration-1.0.xsd” shows a model view of the xsd valiation.xml has to adhere to.

Example 4.1. validation-configuration-1.0.xsd

Example 4.2, “validation.xml” shows the several configuration options of validation.xml.

Example 4.2. 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>org.hibernate.validator.HibernateValidator</default-provider>

    <message-interpolator>org.hibernate.validator.engine.ResourceBundleMessageInterpolator</message-interpolator>

    <traversable-resolver>org.hibernate.validator.engine.resolver.DefaultTraversableResolver</traversable-resolver>

    <constraint-validator-factory>org.hibernate.validator.engine.ConstraintValidatorFactoryImpl</constraint-validator-factory>

    <constraint-mapping>/constraints-car.xml</constraint-mapping>

    <property name="prop1">value1</property>

    <property name="prop2">value2</property>

</validation-config>

Warning

There can only be one validation.xml in the classpath. If more than one is found an exception is thrown.

All settings shown in the validation.xml are optional and in the case of Example 4.2, “validation.xml” show the defaults used within Hibernate Validator. The node default-provider allows to choose the Bean Validation provider. This is useful if there is more than one provider in the classpath. message-interpolator, traversable-resolver and constraint-validator-factory allow to customize the javax.validation.MessageInterpolator, javax.validation.TraversableResolver resp. javax.validation.ConstraintValidatorFactory. The same configuration options are also available programmatically through the javax.validation.Configuration. In fact XML configuration will be overridden by values explicitly specified via the API. It is even possible to ignore the XML configuration completely via Configuration.ignoreXmlConfiguration(). See also Chapter 5, Bootstrapping.

Via the constraint-mapping you can list an arbitrary number of additional XML files containing the actual constraint configuration. See Section 4.2, “Mapping constraints”.

Last but not least, you can specify provider specific properties via the property nodes. Hibernate Validator does currently not make use of any custom properties.

4.2. Mapping constraints

Expressing constraints in XML is possible via files adhering to the xsd seen in Example 4.3, “validation-mapping-1.0.xsd”. Note that these mapping files are only processed if listed via constraint-mapping in your validation.xml.

Example 4.3. validation-mapping-1.0.xsd

Example 4.4, “constraints-car.xml” shows how our classes Car and RentalCar from Example 2.15, “Car” resp. Example 2.19, “RentalCar” could be mapped in XML.

Example 4.4. constraints-car.xml


<constraint-mappings xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

                     xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.0.xsd"

                     xmlns="http://jboss.org/xml/ns/javax/validation/mapping">

    <default-package>org.hibernate.validator.quickstart</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" include-existing-validator="false">

        <validated-by include-existing-validators="false">

            <value>org.mycompany.CheckCaseValidator</value>

        </validated-by>

    </constraint-definition>

</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 classname 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. If the same class is configured more than once an exception is thrown.

Settings 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 and getter. If not explicitly specified on these levels the configured bean value applies. Otherwise do the nodes class, fields and getter determine on which level the constraints are placed (see Section 2.1, “Defining constraints”). 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 the element node.

The class node also allows to reconfigure the default group sequence (see Section 2.3.2, “Redefining the default group sequence of a class”) via the group-sequence node.

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 ConstraintValidators described in XML are concatenated to the list of validators described on the annotation.

Chapter 5. Bootstrapping

5.1. Configuration and ValidatorFactory

5.2. ValidationProviderResolver

5.3. MessageInterpolator

5.3.1. ResourceBundleLocator

5.4. TraversableResolver

5.5. ConstraintValidatorFactory

We already seen in Section 5.1, “Configuration and ValidatorFactory” the easiest way to create a Validator instance - Validation.buildDefaultValidatorFactory. In this chapter we have a look at the other methods in javax.validation.Validation and how they allow to configure several aspects of Bean Validation at bootstrapping time.

The different bootstrapping options allow, amongst other things, to bootstrap any Bean Validation implementation on the classpath. Generally, an available provider is discovered by the Java Service Provider mechanism. A Bean Validation implementation includes the file javax.validation.spi.ValidationProvider in META-INF/services. This file contains the fully qualified classname of the ValidationProvider of the implementation. In the case of Hibernate Validator this is org.hibernate.validator.HibernateValidator.

Note

If there are more than one Bean Validation implementation providers in the classpath and Validation.buildDefaultValidatorFactory() is used, there is no guarantee which provider will be chosen. To enforce the provider Validation.byProvider() should be used.

5.1. `Configuration` and `ValidatorFactory`

There are three different methods in the Validation class to create a Validator instance. The easiest in shown in Example 5.1, “Validation.buildDefaultValidatorFactory()”.

Example 5.1. Validation.buildDefaultValidatorFactory()

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

Validator validator = factory.getValidator();

You can also use the method Validation.byDefaultProvider() which will allow you to configure several aspects of the created Validator instance:

Example 5.2. Validation.byDefaultProvider()

Configuration<?> config = Validation.byDefaultProvider().configure();

config.messageInterpolator(new MyMessageInterpolator())

    .traversableResolver( new MyTraversableResolver())

    .constraintValidatorFactory(new MyConstraintValidatorFactory());


ValidatorFactory factory = config.buildValidatorFactory();

Validator validator = factory.getValidator();

We will learn more about MessageInterpolator, TraversableResolver and ConstraintValidatorFactory in the following sections.

Last but not least you can ask for a Configuration object of a specific Bean Validation provider. This is useful if you have more than one Bean Validation provider in your classpath. In this situation you can make an explicit choice about which implementation to use. In the case of Hibernate Validator the Validator creation looks like:

Example 5.3. Validation.byProvider( HibernateValidator.class )

HibernateValidatorConfiguration config = Validation.byProvider( HibernateValidator.class ).configure();

config.messageInterpolator(new MyMessageInterpolator())

    .traversableResolver( new MyTraversableResolver())

    .constraintValidatorFactory(new MyConstraintValidatorFactory());


ValidatorFactory factory = config.buildValidatorFactory();

Validator validator = factory.getValidator();

Tip

The generated Validator instance is thread safe and can be cached.

5.2. `ValidationProviderResolver`

In the case that the Java Service Provider mechanism does not work in your environment or you have a special classloader setup, you are able to provide a custom ValidationProviderResolver. An example in an OSGi environment you could plug your custom provider resolver like seen in Example 5.4, “Providing a custom ValidationProviderResolver”.

Example 5.4. Providing a custom ValidationProviderResolver

Configuration<?> config = Validation.byDefaultProvider()

    .providerResolver( new OSGiServiceDiscoverer() )

    .configure();


ValidatorFactory factory = config.buildValidatorFactory();

Validator validator = factory.getValidator();

Your OSGiServiceDiscoverer must in this case implement the interface ValidationProviderResolver:

Example 5.5. ValidationProviderResolver interface

public interface ValidationProviderResolver {

    /**

     * Returns a list of ValidationProviders available in the runtime environment.

     *

     * @return list of validation providers.  

     */

    List<ValidationProvider<?>> getValidationProviders();

}

5.3. `MessageInterpolator`

Section 2.2.4, “Message interpolation” already discussed the default message interpolation algorithm. If you have special requirements for your message interpolation you can provide a custom interpolator using Configuration.messageInterpolator(). This message interpolator will be shared by all validators generated by the ValidatorFactory created from this Configuration(see Example 5.6, “Providing a custom MessageInterpolator”).

Example 5.6. Providing a custom MessageInterpolator

Configuration<?> configuration = Validation.byDefaultProvider().configure();

ValidatorFactory factory = configuration

    .messageInterpolator(new ContextualMessageInterpolator(configuration.getDefaultMessageInterpolator()))

    .buildValidatorFactory();


Validator validator = factory.getValidator();

Tip

It is recommended that MessageInterpolator implementations delegate final interpolation to the Bean Validation default MessageInterpolator to ensure standard Bean Validation interpolation rules are followed. The default implementation is accessible through Configuration.getDefaultMessageInterpolator().

5.3.1. ResourceBundleLocator

A common use case is the ability to specify your own resource bundles for message interpolation. The default MessageInterpolator implementation in Hibernate Validator is called ResourceBundleMessageInterpolator and per default loads resource bundles via ResourceBundle.getBundle. However, ResourceBundleMessageInterpolator also allows you to specify a custom implementation of ResourceBundleLocator allowing you to provide your own resource bundles. Example 5.7, “Providing a custom ResourceBundleLocator” shows an example. In the exampleHibernateValidatorConfiguration.getDefaultResourceBundleLocator is used to retrieve the default ResourceBundleLocator which then can be passed to the custom implementation in order implement delegation.

Example 5.7. Providing a custom ResourceBundleLocator

HibernateValidatorConfiguration configure = Validation.byProvider(HibernateValidator.class).configure();


ResourceBundleLocator defaultResourceBundleLocator = configure.getDefaultResourceBundleLocator(); 

ResourceBundleLocator myResourceBundleLocator = new MyCustomResourceBundleLocator(defaultResourceBundleLocator);


configure.messageInterpolator(new ResourceBundleMessageInterpolator(myResourceBundleLocator));

Hibernate Validator provides the following implementation of ResourceBundleLocator - PlatformResourceBundleLocator (the default) and AggregateResourceBundleLocator. The latter can be used to specify a list of resource bundle names which will get loaded and merged into a single resource bundle. Refer to the JavaDoc documentation for more information.

5.4. `TraversableResolver`

The usage of the TraversableResolver has so far not been discussed. The idea is that in some cases, the state of a property should not be accessed. The most obvious example for that is a lazy loaded property or association of a Java Persistence provider. Validating this lazy property or association would mean that its state would have to be accessed triggering a load from the database. Bean Validation controls which property can and cannot be accessed via the TraversableResolver interface (see Example 5.8, “TraversableResolver interface”). In the example HibernateValidatorConfiguration.

Example 5.8. TraversableResolver interface

/**

 * Contract determining if a property can be accessed by the Bean Validation provider

 * This contract is called for each property that is being either validated or cascaded.

 *

 * A traversable resolver implementation must be thread-safe.

 *

 */

public interface TraversableResolver {

    /**

     * Determine if the Bean Validation provider is allowed to reach the property state

     *

     * @param traversableObject object hosting <code>traversableProperty</code> or null  

     *                          if validateValue is called

     * @param traversableProperty the traversable property.

     * @param rootBeanType type of the root object passed to the Validator.

     * @param pathToTraversableObject path from the root object to

     *        <code>traversableObject</code>

     *        (using the path specification defined by Bean Validator).

     * @param elementType either <code>FIELD</code> or <code>METHOD</code>.

     *

     * @return <code>true</code> if the Bean Validation provider is allowed to

     *         reach the property state, <code>false</code> otherwise.

     */

     boolean isReachable(Object traversableObject,

                         Path.Node traversableProperty,

                         Class<?> rootBeanType,

                         Path pathToTraversableObject,

                         ElementType elementType);


    /**

     * Determine if the Bean Validation provider is allowed to cascade validation on

     * the bean instance returned by the property value

     * marked as <code>@Valid</code>.

     * Note that this method is called only if isReachable returns true for the same set of

     * arguments and if the property is marked as <code>@Valid</code>

     *

     * @param traversableObject object hosting <code>traversableProperty</code> or null

     *                          if validateValue is called

     * @param traversableProperty the traversable property.

     * @param rootBeanType type of the root object passed to the Validator.

     * @param pathToTraversableObject path from the root object to

     *        <code>traversableObject</code>

     *        (using the path specification defined by Bean Validator).

     * @param elementType either <code>FIELD</code> or <code>METHOD</code>.

     *

     * @return <code>true</code> if the Bean Validation provider is allowed to

     *         cascade validation, <code>false</code> otherwise.

     */

     boolean isCascadable(Object traversableObject,

                          Path.Node traversableProperty,

                          Class<?> rootBeanType,

                          Path pathToTraversableObject,

                          ElementType elementType);

}

Hibernate Validator provides two TraversableResolvers out of the box which will be enabled automatically depending on your environment. The first is the DefaultTraversableResolver which will always return true for isReachable() and isTraversable(). The second is the JPATraversableResolver which gets enabled when Hibernate Validator gets used in combination with JPA 2. In case you have to provide your own resolver you can do so again using the Configuration object as seen in Example 5.9, “Providing a custom TraversableResolver”.

Example 5.9. Providing a custom TraversableResolver

Configuration<?> configuration = Validation.byDefaultProvider().configure();

ValidatorFactory factory = configuration

    .traversableResolver(new MyTraversableResolver())

    .buildValidatorFactory();


Validator validator = factory.getValidator();

5.5. `ConstraintValidatorFactory`

Last but not least, there is one more configuration option to discuss, the ConstraintValidatorFactory. The default ConstraintValidatorFactory provided by Hibernate Validator requires a public no-arg constructor to instantiate ConstraintValidator instances (see Section 3.1.2, “The constraint validator”). Using a custom ConstraintValidatorFactory offers for example the possibility to use dependency injection in constraint implementations. The configuration of the custom factory is once more via the Configuration (Example 5.10, “Providing a custom ConstraintValidatorFactory”).

Example 5.10. Providing a custom ConstraintValidatorFactory

Configuration<?> configuration = Validation.byDefaultProvider().configure();

ValidatorFactory factory = configuration

    .constraintValidatorFactory(new IOCConstraintValidatorFactory())

    .buildValidatorFactory();


Validator validator = factory.getValidator();

The interface you have to implement is:

Example 5.11. ConstraintValidatorFactory interface

public interface ConstraintValidatorFactory {

    /**

     * @param key The class of the constraint validator to instantiate.

     *

     * @return A constraint validator instance of the specified class.

     */

     <T extends ConstraintValidator<?,?>> T getInstance(Class<T> key);

}

Warning

Any constraint implementation relying on ConstraintValidatorFactory behaviors specific to an implementation (dependency injection, no no-arg constructor and so on) are not considered portable.

Note

ConstraintValidatorFactory should not cache instances as the state of each instance can be altered in the initialize method.

Chapter 6. Integration with other frameworks

6.1. OSGi

6.2. Database schema-level validation

6.3. ORM integration

6.3.1. Hibernate event-based validation
6.3.2. JPA

6.4. Presentation layer validation

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.

6.1. OSGi

The Hibernate Validator jar file is conform to the OSGi specification and can be used within any OSGi container. The classes in the following packages are exported by Hibernate Validator and are considered part of the public API - org.hibernate.validator, org.hibernate.validator.constraints, org.hibernate.validator.messageinterpolation and org.hibernate.validator.resourceloading.

6.2. Database schema-level validation

Out of the box, Hibernate Annotations (as of Hibernate 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, “Built-in 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.

6.3. ORM integration

Hibernate Validator integrates with both Hibernate and all pure Java Persistence providers.

6.3.1. Hibernate event-based validation

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 6.1, “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 6.1. 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>

6.3.2. JPA

If you are using JPA 2 and Hibernate Validator is in the classpath the JPA2 specification requires that Bean Validation gets enabled. The properties javax.persistence.validation.group.pre-persist, javax.persistence.validation.group.pre-update and javax.persistence.validation.group.pre-remove as described in Section 6.3.1, “Hibernate event-based validation” can in this case be configured in persistence.xml. persistence.xml also defines a node validation-mode while 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 6.3.1, “Hibernate event-based validation” to your project and register it manually.

6.4. Presentation layer validation

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 6.2, “Usage of Bean Validation within JSF2” shows an example of the f:validateBean tag in a JSF page. For more information refer to the Seam documentation or the JSF 2 specification.

Example 6.2. Usage of Bean Validation within JSF2

<h:form>
  <f:validateBean>
    <h:inputText value=”#{model.property}” />
    <h:selectOneRadio value=”#{model.radioProperty}” > ... </h:selectOneRadio>
    <!-- other input components here -->
  </f:validateBean>
</h:form>

Chapter 7. Programmatic constraint definition

Note

Use of the features described in the following sections is not portable between Bean Validation providers/implementations.

Hibernate Validator allows to configure constraints not only via annotations and xml, but also via a programmatic API. This API can be used exclusively or in combination with annotations and xml. If used in combination programmatic constraints are additive to otherwise configured constraints.

The programmatic API is centered around the ConstraintMapping class which can be found together with its supporting classes in the org.hibernate.validator.cfg package. ConstraintMapping is the entry point to a fluent API allowing the definition of constraints. Example 7.1, “Programmatic constraint definition” shows how the API can be used.

Example 7.1. Programmatic constraint definition

ConstraintMapping mapping = new ConstraintMapping();
mapping.type( Car.class )
    .property( "manufacturer", FIELD )
        .constraint( NotNullDef.class )
    .property( "licensePlate", FIELD )
        .constraint( NotNullDef.class )
        .constraint( SizeDef.class )
            .min( 2 )
            .max( 14 )
    .property( "seatCount", FIELD )
        .constraint( MinDef.class )
            .value ( 2 )
.type( RentalCar.class )
    .property( "rentalStation", METHOD)
        .constraint( NotNullDef.class );

As you can see you can configure constraints on multiple classes and properties using method chaining. The constraint definition classes NotNullDef, SizeDef and MinDef are helper classes which allow to configure constraint parameters in a type-safe fashion. Definition classes exists for all built-in constraints in the org.hibernate.validator.cfg.defs package. For a custom constraint you can either create your own definition class extending ConstraintDef or you can use GenericConstraintDef as seen in Example 7.2, “Programmatic constraint definition using GenericConstraintDef”.

Example 7.2. Programmatic constraint definition using GenericConstraintDef

ConstraintMapping mapping = new ConstraintMapping();
mapping.type( Car.class )
    .property( "licensePlate", FIELD )
        .constraint( GenericConstraintDef.class )
            .constraintType( CheckCase.class )
            .param( "value", CaseMode.UPPER );

Last but not least, you can also define cascading constraints as well as the default group sequence of an entity.

Example 7.3. Cascading constraints and group redefinition

ConstraintMapping mapping = new ConstraintMapping();
mapping.type( Car.class )
    .valid( "driver", FIELD )
.type( RentalCar.class)
    .defaultGroupSequence( RentalCar.class, CarChecks.class );

Once you have your ConstraintMapping you will have to pass it to the configuration. Since the programmatic configuration is not part of the official Bean Validation specification you will have to get hold of the Hibernate Validator specific configuration instance. See Example 7.4, “Creating a Hibernate Validator specific configuration”.

Example 7.4. Creating a Hibernate Validator specific configuration

ConstraintMapping mapping = new ConstraintMapping();
// configure mapping instance

HibernateValidatorConfiguration config = Validation.byProvider( HibernateValidator.class ).configure();
config.addMapping( mapping );
ValidatorFactory factory = config.buildValidatorFactory();
Validator validator = factory.getValidator();

Chapter 8. Annotation Processor (EXPERIMENTAL)

8.1. Prerequisites

8.2. Features

8.3. Options

8.4. Using the Annotation Processor

8.4.1. Command line builds
8.4.2. IDE builds

8.5. Known issues

Have you ever caught yourself by unintentionally doing things like

annotating Strings with @Min to specify a minimum length (instead of using @Size)
annotating the setter of a JavaBean 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.

Warning

A first version of the Hibernate Validator Annotation Processor is part of Hibernate Validator since release 4.1. It is currently still under development and should therefore be considered as an experimental feature. Some known issues can be found at the end of this chapter. In case any problems arise when using the processor feel free to ask for help at the forum or create an issue within JIRA.

8.1. Prerequisites

The Hibernate Validator Annotation Processor is based on the "Pluggable Annotation Processing API" as defined by JSR 269. This API is part of the Java Platform since Java 6. So be sure to use this or a later version.

8.2. Features

As of Hibernate Validator 4.1 the Hibernate Validator Annotation Processor checks that:

constraint annotations are allowed for the type of the annotated element
JavaBean getter methods are annotated in case of property validation
only non-static fields or properties are annotated with constraint annotations
only non-primitive fields or properties are annotated with @Valid
only such annotation types are annotated with constraint annotations which are constraint annotations themselves

8.3. Options

The behavior of the Hibernate Validator Annotation Processor can be controlled using the processor options listed in tableTable 8.1, “Hibernate Validator Annotation Processor options”:

Table 8.1. 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`.
`verbose`	Controls whether detailed processing information shall be displayed or not, useful for debugging purposes. Must be either `true` or`false`. Defaults to `false`.

8.4. Using the Annotation Processor

This section shows in detail how to integrate the Hibernate Validator Annotation Processor into command line builds (javac, Ant, Maven) as well as IDE-based builds (Eclipse, IntelliJ IDEA, NetBeans).

8.4.1. Command line builds

8.4.1.1. javac

When compiling on the command line using javac, specify the following JARs using the "processorpath" option:

validation-api-1.0.0.GA.jar
hibernate-validator-annotation-processor-4.1.0.Final.jar

The following listing shows an example. The processor will be detected automatically by the compiler and invoked during compilation.

Example 8.1. Using the annotation processor with javac

javac src/main/java/org/hibernate/validator/ap/demo/Car.java \
   -cp /path/to/validation-api-1.0.0.GA.jar \ 
   -processorpath /path/to/validation-api-1.0.0.GA.jar:/path/to/hibernate-validator-annotation-processor-4.1.0.Final.jar

8.4.1.2. Apache Ant

Example 8.2. Using the annotation processor with Ant

<javac srcdir="src/main"
       destdir="build/classes"
       classpath="/path/to/validation-api-1.0.0.GA.jar">
       <compilerarg value="-processorpath" />
       <compilerarg value="/path/to/validation-api-1.0.0.GA.jar:/path/to/hibernate-validator-annotation-processor-4.1.0.Final.jar"/>
</javac>

8.4.1.3. Maven

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 8.3. Adding the HV Annotation Processor as dependency

...
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-validator-annotation-processor</artifactId>
    <version>4.1.0.Final</version>
    <scope>compile</scope>
</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. At the time of this writing the plugin is not yet available in any of the well-known repositories. Therefore you have to add the project's own repository to your settings.xml or pom.xml:

Example 8.4. Adding the Maven Annotation Plugin repository

...
<pluginRepositories>
    <pluginRepository>
        <id>maven-annotation-plugin-repo</id>
        <url>http://maven-annotation-plugin.googlecode.com/svn/trunk/mavenrepo</url>
    </pluginRepository>
</pluginRepositories>
...

Now 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 AP is not visible on the project's actual classpath):

Example 8.5. 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>1.3.4</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>4.1.0.Final</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
</plugin>
...

8.4.2. IDE builds

8.4.2.1. Eclipse

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 following JARs:
- validation-api-1.0.0.GA.jar
- hibernate-validator-annotation-processor-4.1.0.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:

8.4.2.2. IntelliJ IDEA

The following steps must be followed to use the annotation processor within IntelliJ IDEA (version 9 and above):

Go to "File", then "Settings",
Expand the node "Compiler", then "Annotation Processors"
Choose "Enable annotation processing" and enter the following as "Processor path": /path/to/validation-api-1.0.0.GA.jar:/path/to/hibernate-validator-annotation-processor-4.1.0.Final.jar
Add the processor's fully qualified name org.hibernate.validator.ap.ConstraintValidationProcessor to the "Annotation Processors" list
If applicable add you module to the "Processed Modules" list

Rebuilding your project then should show any erronous constraint annotations:

8.4.2.3. NetBeans

Starting with version 6.9, also the NetBeans IDE supports using annotation processors within the IDE build. To do so, do the following:

Right-click your project, choose "Properties"
Go to "Libraries", tab "Processor", and add the following two JARs:
- validation-api-1.0.0.GA.jar
- hibernate-validator-annotation-processor-4.1.0.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:

8.5. Known issues

The following known issues exist as of May 2010:

HV-308: Additional validators registered for a constraint using XML are not evaluated by the annotation processor.
Sometimes custom constraints can't be properly evaluated when using the processor within Eclipse. Cleaning the project can help in these situations. This seems to be an issue with the Eclipse JSR 269 API implementation, but further investigation is required here.

Chapter 9. Further reading

Last but not least, a few pointers to further information. A great source for examples is the Bean Validation TCK which can is available for anonymous access in the Hibernate SVN repository. Alternatively you can view the tests using Hibernate's fisheye installation. The JSR 303 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!