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Chapter 18. Bean Validation Support

Validation is a process of verifying that some data obeys one or more pre-defined constraints. This chapter describes support for Bean Validation in Jersey in terms of the needed dependencies, configuration, registration and usage. For more detailed description on how JAX-RS provides native support for validating resource classes based on the Bean Validation refer to the chapter in the JAX-RS spec.

18.1. Bean Validation Dependencies

Bean Validation support in Jersey is provided as an extension module and needs to be mentioned explicitly in your pom.xml file (in case of using Maven):

<dependency>
    <groupId>org.glassfish.jersey.ext</groupId>
    <artifactId>jersey-bean-validation</artifactId>
    <version>2.16</version>
</dependency>

Note

If you're not using Maven make sure to have also all the transitive dependencies (see jersey-bean-validation) on the classpath.

This module depends directly on Hibernate Validator which provides a most commonly used implementation of the Bean Validation API spec.

If you want to use a different implementation of the Bean Validation API, use standard Maven mechanisms to exclude Hibernate Validator from the modules dependencies and add a dependency of your own.

<dependency>
    <groupId>org.glassfish.jersey.ext</groupId>
    <artifactId>jersey-bean-validation</artifactId>
    <version>2.16</version>
    <exclusions>
        <exclusion>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
        </exclusion>
    </exclusions>
</dependency>

18.2. Enabling Bean Validation in Jersey

As stated in Section 4.3, “Auto-Discoverable Features”, Jersey Bean Validation is one of the modules where you don't need to explicitly register it's Features (ValidationFeature) on the server as it's features are automatically discovered and registered when you add the jersey-bean-validation module to your classpath. There are three Jersey specific properties that could disable automatic discovery and registration of Jersey Bean Validation integration module:

Note

Jersey does not support Bean Validation on the client at the moment.

18.3. Configuring Bean Validation Support

Configuration of Bean Validation support in Jersey is twofold - there are few specific properties that affects Jersey behaviour (e.g. sending validation error entities to the client) and then there is ValidationConfig class that configures Validator used for validating resources in JAX-RS application.

To configure Jersey specific behaviour you can use the following properties:

ServerProperties.BV_DISABLE_VALIDATE_ON_EXECUTABLE_OVERRIDE_CHECK

Disables @ValidateOnExecution check. More on this is described in Section 18.5, “@ValidateOnExecution”.

ServerProperties.BV_SEND_ERROR_IN_RESPONSE

Enables sending validation errors in response entity to the client. More on this in Section 18.7.1, “ValidationError”.

Example 18.1. Configuring Jersey specific properties for Bean Validation.

new ResourceConfig()
    // Now you can expect validation errors to be sent to the client.
    .property(ServerProperties.BV_SEND_ERROR_IN_RESPONSE, true)
    // @ValidateOnExecution annotations on subclasses won't cause errors.
    .property(ServerProperties.BV_DISABLE_VALIDATE_ON_EXECUTABLE_OVERRIDE_CHECK, true)
    // Further configuration of ResourceConfig.
    .register( ... );


Customization of the Validator used in validation of resource classes/methods can be done using ValidationConfig class and exposing it via ContextResolver<T> mechanism as shown in Example 18.2, “Using ValidationConfig to configure Validator.”. You can set custom instances for the following interfaces from the Bean Validation API:

Example 18.2. Using ValidationConfig to configure Validator.

/**
 * Custom configuration of validation. This configuration defines custom:
 * <ul>
 *     <li>ConstraintValidationFactory - so that validators are able to inject Jersey providers/resources.</li>
 *     <li>ParameterNameProvider - if method input parameters are invalid, this class returns actual parameter names
 *     instead of the default ones ({@code arg0, arg1, ..})</li>
 * </ul>
 */
public class ValidationConfigurationContextResolver implements ContextResolver<ValidationConfig> {

    @Context
    private ResourceContext resourceContext;

    @Override
    public ValidationConfig getContext(final Class<?> type) {
        final ValidationConfig config = new ValidationConfig();
        config.setConstraintValidatorFactory(resourceContext.getResource(InjectingConstraintValidatorFactory.class));
        config.setParameterNameProvider(new CustomParameterNameProvider());
        return config;
    }

    /**
     * See ContactCardTest#testAddInvalidContact.
     */
    private class CustomParameterNameProvider implements ParameterNameProvider {

        private final ParameterNameProvider nameProvider;

        public CustomParameterNameProvider() {
            nameProvider = Validation.byDefaultProvider().configure().getDefaultParameterNameProvider();
        }

        @Override
        public List<String> getParameterNames(final Constructor<?> constructor) {
            return nameProvider.getParameterNames(constructor);
        }

        @Override
        public List<String> getParameterNames(final Method method) {
            // See ContactCardTest#testAddInvalidContact.
            if ("addContact".equals(method.getName())) {
                return Arrays.asList("contact");
            }
            return nameProvider.getParameterNames(method);
        }
    }
}

Register this class in your app:

final Application application = new ResourceConfig()
        // Validation.
        .register(ValidationConfigurationContextResolver.class)
        // Further configuration.
        .register( ... );

Note

This code snippet has been taken from Bean Validation example.


18.4. Validating JAX-RS resources and methods

JAX-RS specification states that constraint annotations are allowed in the same locations as the following annotations: @MatrixParam, @QueryParam, @PathParam, @CookieParam, @HeaderParam and @Context, except in class constructors and property setters. Specifically, they are allowed in resource method parameters, fields and property getters as well as resource classes, entity parameters and resource methods (return values). Jersey provides support for validation (see following sections) annotated input parameters and return value of the invoked resource method as well as validation of resource class (class constraints, field constraints) where this resource method is placed. Jersey does not support, and doesn't validate, constraints placed on constructors and Bean Validation groups (only Default group is supported at the moment).

18.4.1. Constraint Annotations

The JAX-RS Server API provides support for extracting request values and mapping them into Java fields, properties and parameters using annotations such as @HeaderParam, @QueryParam, etc. It also supports mapping of the request entity bodies into Java objects via non-annotated parameters (i.e., parameters without any JAX-RS annotations).

The Bean Validation specification supports the use of constraint annotations as a way of declaratively validating beans, method parameters and method returned values. For example, consider resource class from Example 18.3, “Constraint annotations on input parameters” augmented with constraint annotations.

Example 18.3. Constraint annotations on input parameters

@Path("/")
class MyResourceClass {

    @POST
    @Consumes("application/x-www-form-urlencoded")
    public void registerUser(
            @NotNull @FormParam("firstName") String firstName,
            @NotNull @FormParam("lastName") String lastName,
            @Email @FormParam("email") String email) {
        ...
    }
}


The annotations @NotNull and @Email impose additional constraints on the form parameters firstName, lastName and email. The @NotNull constraint is built-in to the Bean Validation API; the @Email constraint is assumed to be user defined in the example above. These constraint annotations are not restricted to method parameters, they can be used in any location in which JAX-RS binding annotations are allowed with the exception of constructors and property setters.

Rather than using method parameters, the MyResourceClass shown above could have been written as in Example 18.4, “Constraint annotations on fields”.

Example 18.4. Constraint annotations on fields

@Path("/")
class MyResourceClass {

    @NotNull
    @FormParam("firstName")
    private String firstName;

    @NotNull
    @FormParam("lastName")
    private String lastName;

    private String email;

    @FormParam("email")
    public void setEmail(String email) {
        this.email = email;
    }

    @Email
    public String getEmail() {
        return email;
    }

    ...
}


Note that in this version, firstName and lastName are fields initialized via injection and email is a resource class property. Constraint annotations on properties are specified in their corresponding getters.

Constraint annotations are also allowed on resource classes. In addition to annotating fields and properties, an annotation can be defined for the entire class. Let us assume that @NonEmptyNames validates that one of the two name fields in MyResourceClass is provided. Using such an annotation, the example above can be extended to look like Example 18.5, “Constraint annotations on class”

Example 18.5. Constraint annotations on class

@Path("/")
@NonEmptyNames
class MyResourceClass {

    @NotNull
    @FormParam("firstName")
    private String firstName;

    @NotNull
    @FormParam("lastName")
    private String lastName;

    private String email;

    ...
}


Constraint annotations on resource classes are useful for defining cross-field and cross-property constraints.

18.4.2. Annotation constraints and Validators

Annotation constraints and validators are defined in accordance with the Bean Validation specification. The @Email annotation used in Example 18.4, “Constraint annotations on fields” is defined using the Bean Validation @Constraint meta-annotation, see Example 18.6, “Definition of a constraint annotation”.

Example 18.6. Definition of a constraint annotation

@Target({ METHOD, FIELD, PARAMETER })
@Retention(RUNTIME)
@Constraint(validatedBy = EmailValidator.class)
public @interface Email {

    String message() default "{com.example.validation.constraints.email}";

    Class<?>[] groups() default {};

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


The @Constraint annotation must include a reference to the validator class that will be used to validate decorated values. The EmailValidator class must implement ConstraintValidator<Email, T> where T is the type of values being validated, as described in Example 18.7, “Validator implementation.”.

Example 18.7. Validator implementation.

public class EmailValidator implements ConstraintValidator<Email, String> {

    public void initialize(Email email) {
        ...
    }

    public boolean isValid(String value, ConstraintValidatorContext context) {
        ...
    }
}


Thus, EmailValidator applies to values annotated with @Email that are of type String. Validators for other Java types can be defined for the same constraint annotation.

18.4.3. Entity Validation

Request entity bodies can be mapped to resource method parameters. There are two ways in which these entities can be validated. If the request entity is mapped to a Java bean whose class is decorated with Bean Validation annotations, then validation can be enabled using @Valid as in Example 18.8, “Entity validation”.

Example 18.8. Entity validation

@StandardUser
class User {

    @NotNull
    private String firstName;

    ...
}


@Path("/")
class MyResourceClass {

    @POST
    @Consumes("application/xml")
    public void registerUser(@Valid User user) {
        ...
    }
}


In this case, the validator associated with @StandardUser (as well as those for non-class level constraints like @NotNull) will be called to verify the request entity mapped to user.

Alternatively, a new annotation can be defined and used directly on the resource method parameter (Example 18.9, “Entity validation 2”).

Example 18.9. Entity validation 2

@Path("/")
class MyResourceClass {

    @POST
    @Consumes("application/xml")
    public void registerUser(@PremiumUser User user) {
        ...
    }
}


In the example above, @PremiumUser rather than @StandardUser will be used to validate the request entity. These two ways in which validation of entities can be triggered can also be combined by including @Valid in the list of constraints. The presence of @Valid will trigger validation of all the constraint annotations decorating a Java bean class.

Response entity bodies returned from resource methods can be validated in a similar manner by annotating the resource method itself. To exemplify, assuming both @StandardUser and @PremiumUser are required to be checked before returning a user, the getUser method can be annotated as shown in Example 18.10, “Response entity validation”.

Example 18.10. Response entity validation

@Path("/")
class MyResourceClass {

    @GET
    @Path("{id}")
    @Produces("application/xml")
    @Valid @PremiumUser
    public User getUser(@PathParam("id") String id) {
        User u = findUser(id);
        return u;
    }

    ...
}


Note that @PremiumUser is explicitly listed and @StandardUser is triggered by the presence of the @Valid annotation - see definition of User class earlier in this section.

18.4.4. Annotation Inheritance

The rules for inheritance of constraint annotation are defined in Bean Validation specification. It is worth noting that these rules are incompatible with those defined by JAX-RS. Generally speaking, constraint annotations in Bean Validation are cumulative (can be strengthen) across a given type hierarchy while JAX-RS annotations are inherited or, overridden and ignored.

For Bean Validation annotations Jersey follows the constraint annotation rules defined in the Bean Validation specification.

18.5. @ValidateOnExecution

According to Bean Validation specification, validation is enabled by default only for the so called constrained methods. Getter methods as defined by the Java Beans specification are not constrained methods, so they will not be validated by default. The special annotation @ValidateOnExecution can be used to selectively enable and disable validation. For example, you can enable validation on method getEmail shown in Example 18.11, “Validate getter on execution”.

Example 18.11. Validate getter on execution

@Path("/")
class MyResourceClass {

    @Email
    @ValidateOnExecution
    public String getEmail() {
        return email;
    }

    ...
}


The default value for the type attribute of @ValidateOnExecution is IMPLICIT which results in method getEmail being validated.

Note

According to Bean Validation specification @ValidateOnExecution cannot be overridden once is declared on a method (i.e. in subclass/sub-interface) and in this situations a ValidationException should be raised. This default behaviour can be suppressed by setting ServerProperties.BV_DISABLE_VALIDATE_ON_EXECUTABLE_OVERRIDE_CHECK property (Jersey specific) to true.

18.6. Injecting

Jersey allows you to inject registered resources/providers into your ConstraintValidator implementation and you can inject Configuration, ValidatorFactory and Validator as required by Bean Validation spec.

Note

Injected Configuration, ValidatorFactory and Validator do not inherit configuration provided by ValidationConfig and need to be configured manually.

Injection of JAX-RS components into ConstraintValidators is supported via a custom ConstraintValidatorFactory provided by Jersey. An example is shown in Example 18.12, “Injecting UriInfo into a ConstraintValidator”.

Example 18.12. Injecting UriInfo into a ConstraintValidator

public class EmailValidator implements ConstraintValidator<Email, String> {

    @Context
    private UriInfo uriInfo;

    public void initialize(Email email) {
        ...
    }

    public boolean isValid(String value, ConstraintValidatorContext context) {
        // Use UriInfo.

        ...
    }
}


Using a custom ConstraintValidatorFactory of your own disables registration of the one provided by Jersey and injection support for resources/providers (if needed) has to be provided by this new implementation. Example 18.13, “Support for injecting Jersey's resources/providers via ConstraintValidatorFactory.” shows how this can be achieved.

Example 18.13. Support for injecting Jersey's resources/providers via ConstraintValidatorFactory.

public class InjectingConstraintValidatorFactory implements ConstraintValidatorFactory {

    @Context
    private ResourceContext resourceContext;

    @Override
    public <T extends ConstraintValidator<?, ?>> T getInstance(final Class<T> key) {
        return resourceContext.getResource(key);
    }

    @Override
    public void releaseInstance(final ConstraintValidator<?, ?> instance) {
        // NOOP
    }
}


Note

This behaviour may likely change in one of the next version of Jersey to remove the need of manually providing support for injecting resources/providers from Jersey in your own ConstraintValidatorFactory implementation code.

18.7. Error Reporting

Bean Validation specification defines a small hierarchy of exceptions (they all inherit from ValidationException) that could be thrown during initialization of validation engine or (for our case more importantly) during validation of input/output values (ConstraintViolationException). If a thrown exception is a subclass of ValidationException except ConstraintViolationException then this exception is mapped to a HTTP response with status code 500 (Internal Server Error). On the other hand, when a ConstraintViolationException is throw two different status code would be returned:

  • 500 (Internal Server Error)

    If the exception was thrown while validating a method return type.

  • 400 (Bad Request)

    Otherwise.

18.7.1. ValidationError

By default, (during mapping ConstraintViolationExceptions) Jersey doesn't return any entities that would include validation errors to the client. This default behaviour could be changed by enabling ServerProperties.BV_SEND_ERROR_IN_RESPONSE property in your application (Example 18.1, “Configuring Jersey specific properties for Bean Validation.”). When this property is enabled then our custom ExceptionMapper<E extends Throwable> (that is handling ValidationExceptions) would transform ConstraintViolationException(s) into ValidationError(s) and set this object (collection) as the new response entity which Jersey is able to sent to the client. Four MediaTypes are currently supported when sending ValidationErrors to the client:

  • text/plain

  • text/html

  • application/xml

  • application/json

    Note

    Note: You need to register one of the JSON (JAXB) providers (e.g. MOXy) to marshall validation errors to JSON.

Let's take a look at ValidationError class to see which properties are send to the client:

@XmlRootElement
public final class ValidationError {

    private String message;

    private String messageTemplate;

    private String path;

    private String invalidValue;

    ...
}

The message property is the interpolated error message, messageTemplate represents a non-interpolated error message (or key from your constraint definition e.g. {javax.validation.constraints.NotNull.message}), path contains information about the path in the validated object graph to the property holding invalid value and invalidValue is the string representation of the invalid value itself.

Here are few examples of ValidationError messages sent to client:

Example 18.14. ValidationError to text/plain

HTTP/1.1 500 Internal Server Error
Content-Length: 114
Content-Type: text/plain
Vary: Accept
Server: Jetty(6.1.24)

Contact with given ID does not exist. (path = ContactCardResource.getContact.<return value>, invalidValue = null)


Example 18.15. ValidationError to text/html

HTTP/1.1 500 Internal Server Error
Content-Length: ...
Content-Type: text/plain
Vary: Accept
Server: Jetty(6.1.24)

<div class="validation-errors">
    <div class="validation-error">
        <span class="message">Contact with given ID does not exist.</span>
        (
        <span class="path">
            <strong>path</strong>
            = ContactCardResource.getContact.<return value>
        </span>
        ,
        <span class="invalid-value">
            <strong>invalidValue</strong>
            = null
        </span>
        )
    </div>
</div>


Example 18.16. ValidationError to application/xml

HTTP/1.1 500 Internal Server Error
Content-Length: ...
Content-Type: text/plain
Vary: Accept
Server: Jetty(6.1.24)

<?xml version="1.0" encoding="UTF-8"?>
<validationErrors>
    <validationError>
        <message>Contact with given ID does not exist.</message>
        <messageTemplate>{contact.does.not.exist}</messageTemplate>
        <path>ContactCardResource.getContact.&lt;return value&gt;</path>
    </validationError>
</validationErrors>


Example 18.17. ValidationError to application/json

HTTP/1.1 500 Internal Server Error
Content-Length: 174
Content-Type: application/json
Vary: Accept
Server: Jetty(6.1.24)

[ {
   "message" : "Contact with given ID does not exist.",
   "messageTemplate" : "{contact.does.not.exist}",
   "path" : "ContactCardResource.getContact.<return value>"
} ]


18.8. Example

To see a complete working example of using Bean Validation (JSR-349) with Jersey refer to the Bean Validation Example.