/*
 * Bean Validation API
 *
 * License: Apache License, Version 2.0
 * See the license.txt file in the root directory or <http://www.apache.org/licenses/LICENSE-2.0>.
 */
package javax.validation;

import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import javax.validation.constraintvalidation.SupportedValidationTarget;
import javax.validation.constraintvalidation.ValidationTarget;

Marks an annotation as being a Bean Validation constraint.

A given constraint annotation must be annotated by a @Constraint annotation which refers to its list of constraint validation implementations.

Each constraint annotation must host the following attributes:

  • String message() default [...]; which should default to an error message key made of the fully-qualified class name of the constraint followed by .message. For example "{com.acme.constraints.NotSafe.message}"
  • Class<?>[] groups() default {}; for user to customize the targeted groups
  • Class<? extends Payload>[] payload() default {}; for extensibility purposes

When building a constraint that is both generic and cross-parameter, the constraint annotation must host the validationAppliesTo() property. A constraint is generic if it targets the annotated element and is cross-parameter if it targets the array of parameters of a method or constructor.

    ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;
This property allows the constraint user to choose whether the constraint targets the return type of the executable or its array of parameters. A constraint is both generic and cross-parameter if Such dual constraints are rare. See SupportedValidationTarget for more info.

Here is an example of constraint definition:

@Documented
@Constraint(validatedBy = OrderNumberValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE })
@Retention(RUNTIME)
public @interface OrderNumber {
    String message() default "{com.acme.constraint.OrderNumber.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}
Author:Emmanuel Bernard, Gavin King, Hardy Ferentschik
/** * Marks an annotation as being a Bean Validation constraint. * <p> * A given constraint annotation must be annotated by a {@code @Constraint} * annotation which refers to its list of constraint validation implementations. * <p> * Each constraint annotation must host the following attributes: * <ul> * <li>{@code String message() default [...];} which should default to an error * message key made of the fully-qualified class name of the constraint followed by * {@code .message}. For example {@code "{com.acme.constraints.NotSafe.message}"}</li> * <li>{@code Class<?>[] groups() default {};} for user to customize the targeted * groups</li> * <li>{@code Class<? extends Payload>[] payload() default {};} for * extensibility purposes</li> * </ul> * <p> * When building a constraint that is both generic and cross-parameter, the constraint * annotation must host the {@code validationAppliesTo()} property. * A constraint is generic if it targets the annotated element and is cross-parameter if * it targets the array of parameters of a method or constructor. * <pre> * ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT; * </pre> * This property allows the constraint user to choose whether the constraint * targets the return type of the executable or its array of parameters. * * A constraint is both generic and cross-parameter if * <ul> * <li>two kinds of {@code ConstraintValidator}s are attached to the * constraint, one targeting {@link ValidationTarget#ANNOTATED_ELEMENT} * and one targeting {@link ValidationTarget#PARAMETERS},</li> * <li>or if a {@code ConstraintValidator} targets both * {@code ANNOTATED_ELEMENT} and {@code PARAMETERS}.</li> * </ul> * * Such dual constraints are rare. See {@link SupportedValidationTarget} for more info. * <p> * Here is an example of constraint definition: * <pre> * &#64;Documented * &#64;Constraint(validatedBy = OrderNumberValidator.class) * &#64;Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE }) * &#64;Retention(RUNTIME) * public &#64;interface OrderNumber { * String message() default "{com.acme.constraint.OrderNumber.message}"; * Class&lt;?&gt;[] groups() default {}; * Class&lt;? extends Payload&gt;[] payload() default {}; * } * </pre> * * @author Emmanuel Bernard * @author Gavin King * @author Hardy Ferentschik */
@Documented @Target({ ANNOTATION_TYPE }) @Retention(RUNTIME) public @interface Constraint {
ConstraintValidator classes implementing the constraint. The given classes must reference distinct target types for a given ValidationTarget. If two ConstraintValidators refer to the same type, an exception will occur.

At most one ConstraintValidator targeting the array of parameters of methods or constructors (aka cross-parameter) is accepted. If two or more are present, an exception will occur.

Returns:array of ConstraintValidator classes implementing the constraint
/** * {@link ConstraintValidator} classes implementing the constraint. The given classes * must reference distinct target types for a given {@link ValidationTarget}. If two * {@code ConstraintValidator}s refer to the same type, an exception will occur. * <p> * At most one {@code ConstraintValidator} targeting the array of parameters of * methods or constructors (aka cross-parameter) is accepted. If two or more * are present, an exception will occur. * * @return array of {@code ConstraintValidator} classes implementing the constraint */
Class<? extends ConstraintValidator<?, ?>>[] validatedBy(); }