Validating Resource Data with Bean Validation

JAX-RS supports the Bean Validation to verify JAX-RS resource classes. This support consists of:

Adding constraint annotations to resource method parameters
Ensuring entity data is valid when the entity is passed in as a parameter

The following topics are addressed here:

Using Constraint Annotations on Resource Methods
Validating Entity Data
Validation Exception Handling and Response Codes

Using Constraint Annotations on Resource Methods

Bean Validation constraint annotations may be applied to parameters for a resource. The server will validate the parameters and either pass or throw a javax.validation.ValidationException.

@POST
@Path("/createUser")
@Consumes(MediaType.APPLICATION_FORM_URLENCODED)
public void createUser(@NotNull @FormParam("username") String username,
                       @NotNull @FormParam("firstName") String firstName,
                       @NotNull @FormParam("lastName") String lastName,
                       @Email @FormParam("email") String email) {
    ...
}

In the preceding example, the built-in constraint @NotNull is applied to the username, firstName, and lastName form fields. Another built-in constraint @Email validates that the email address supplied by the email form field is correctly formatted.

The constraints may also be applied to fields within a resource class.

@Path("/createUser")
public class CreateUserResource {
  @NotNull
  @FormParam("username")
  private String username;

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

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

  @Email
  @FormParam("email")
  private String email;

  ...
}

In the preceding example, the same constraints that were applied to the method parameters in the previous example are applied to the class fields. The behavior is the same in both examples.

Constraints may also be applied to a resource class’s JavaBeans properties by adding the constraint annotations to the getter method.

@Path("/createuser")
public class CreateUserResource {
  private String username;

  @FormParam("username")
  public void setUsername(String username) {
    this.username = username;
  }

  @NotNull
  public String getUsername() {
    return username;
  }
  ...
}

Constraints may also be applied at the resource class level. In the following example, @PhoneRequired is a user-defined constraint that ensures that a user enters at least one phone number. That is, either homePhone or mobilePhone can be null, but not both.

@Path("/createUser")
@PhoneRequired
public class CreateUserResource {
  @FormParam("homePhone")
  private Phone homePhone;

  @FormParam("mobilePhone")
  private Phone mobilePhone;
  ...
}

Validating Entity Data

Classes that contain validation constraint annotations may be used in method parameters in a resource class. To validate these entity classes, use the @Valid annotation on the method parameter. For example, the following class is a user-defined class containing both standard and user-defined validation constraints.

@PhoneRequired
public class User {
  @NotNull
  private String username;

  private Phone homePhone;

  private Phone mobilePhone;
  ...
}

This entity class is used as a parameter to a resource method.

@Path("/createUser")
public class CreateUserResource {
  ...
  @POST
  @Consumers(MediaType.APPLICATION_XML)
  public void createUser(@Valid User user) {
    ...
  }
  ...
}

The @Valid annotation ensures that the entity class is validated at runtime. Additional user-defined constraints can also trigger validation of an entity.

@Path("/createUser")
public class CreateUserResource {
  ...
  @POST
  @Consumers(MediaType.APPLICATION_XML)
  public void createUser(@ActiveUser User user) {
    ...
  }
  ...
}

In the preceding example, the user-defined @ActiveUser constraint is applied to the User class in addition to the @PhoneRequired and @NotNull constraints defined within the entity class.

If a resource method returns an entity class, validation may be triggered by applying the @Valid or any other user-defined constraint annotation to the resource method.

@Path("/getUser")
public class GetUserResource {
  ...
  @GET
  @Path("{username}")
  @Produces(MediaType.APPLICATION_XML)
  @ActiveUser
  @Valid
  public User getUser(@PathParam("username") String username) {
    // find the User
    return user;
  }
  ...
}

As in the previous example, the @ActiveUser constraint is applied to the returned entity class as well as the @PhoneRequired and @NotNull constraints defined within the entity class.

Validation Exception Handling and Response Codes

If a javax.validation.ValidationException or any subclass of ValidationException except ConstraintValidationException is thrown, the JAX-RS runtime will respond to the client request with a 500 (Internal Server Error) HTTP status code.

If a ConstraintValidationException is thrown, the JAX-RS runtime will respond to the client with one of the following HTTP status codes:

500 (Internal Server Error) if the exception was thrown while validating a method return type
400 (Bad Request) in all other cases