Java Bean Validation - Predefined constraints

Java Bean validation specification defines following constraint annotations in package javax.validation.constraints:

Details:

Other optional parameters

All above annotations have these additional parameters (including which are showing 'None'):

• message=String:

  The validation error to be displayed as a message.

  Defaulted to built-in resource bundle keys for i18n purpose.

  The default can be overridden by a hard coded message string literal or a new application defined resource bundle key.

  Resource keys are used within {}.

  The default resource key is the fully qualified name of the annotation class concatenated to .message, e.g. javax.validation.constraints.Future.message. we should follow the same convention when creating custom constraint annotations.

  
  

• groups=Class<?>[]

  This is a way to group constraints. The validation evaluation can be restricted to certain group(s) of annotation based on the class types defined here. We can specify groups while calling Validator#validate(..) method.

  
  

• payload=Class<? extends Payload>[]

  This is a way to associate some metadata information with a given constraint annotation declaration.

  
  

Note that all above three parameters are optional on client side but when creating new custom constraint annotations, we have to include all these three parameter definitions as it is, otherwise we will have javax.validation.ConstraintDefinitionException.

List constraints

For each of the above predefined annotations, there is an inner annotation type named List.

For example let's have a look at NotNull definition:

Definition of NotNull

package javax.validation.constraints;
   ........
@Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
@Retention(RUNTIME)
@Repeatable(List.class)
@Documented
@Constraint(validatedBy = {})
public @interface NotNull {
    String message() default "{javax.validation.constraints.NotNull.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
    @Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
    @Retention(RUNTIME)
    @Documented
    @interface List {
        NotNull[] value();
    }
}

This annotation generally allows to specify several annotations on the same element, e.g. with different validation groups and messages.

Bean Validation 2.0 (JSR 380) Changes

• New built-in constraints (as seen in above table):
  @Email, @NotEmpty, @NotBlank, @Positive, @PositiveOrZero, @Negative, @NegativeOrZero, @PastOrPresent and @FutureOrPresent
• All constraint annotations have been annotated with Java 8 @Repeatable annotation.
• All constraint annotation can be used as Java 8 Type Annotations, i.e. their @Target now includes ElementType.TYPE_USE.