/* * Copyright 2006 Amazon Technologies, Inc. or its affiliates. * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks * of Amazon Technologies, Inc. or its affiliates. All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.amazon.carbonado.constraint; import java.lang.annotation.*; /** * Allows annotations to be defined that restrict property values. The * annotation is just a pointer to a constraint checking class. If the * constraint class is not explicitly provided, it defaults to a static inner * class named "Constraint" in the annotation itself. * *

The constraint class must have a public constructor that accepts the * annotation that has the ConstraintDefinition annotation. It must also define * several "constrain" methods which perform constraint checks on specific * property types. *

* Example integer constraint: *

 * @Documented
 * @Retention(RetentionPolicy.RUNTIME)
 * @Target(ElementType.METHOD)
 * @ConstraintDefinition
 * public @interface IntegerConstraint {
 *     int min() default Integer.MIN_VALUE;
 *
 *     int max() default Integer.MAX_VALUE;
 *
 *     public static class Constraint {
 *         private final String propertyName;
 *         private final int min;
 *         private final int max;
 *
 *         // Constructor may throw a MalformedTypeException if
 *         // params supplied by annotation are illegal.
 *
 *         /**
 *          * @param type optional type of object that contains the constrained property
 *          * @param propertyName name of property with constraint
 *          * @param annotation specific annotation that binds to this constraint class
 *          */
 *         public Constraint(Class type, String propertyName, IntegerConstraint annotation) {
 *             this.propertyName = propertyName;
 *             this.min = annotation.min();
 *             this.max = annotation.max();
 *         }
 *
 *         // Define a constrain method for each supported property type.
 *
 *         /**
 *          * @param propertyValue specific value to constrain
 *          */
 *         public void constrain(int propertyValue) throws IllegalArgumentException {
 *             if (propertyValue < min || propertyValue > max) {
 *                 throw new IllegalArgumentException
 *                     ("Value for \"" + propertyName + "\" must be in range " +
 *                      min + ".." + max + ": " + propertyValue);
 *             }
 *         }
 *     }
 * }
 * 
* * The newly defined integer constraint can be applied to property mutators. * *
 * public interface UserInfo extends Storable {
 *     ...
 *
 *     int getAge();
 *     // Constraint is called before setting age.
 *     @IntegerConstraint(min=0, max=120)
 *     void setAge(int value);
 * }
 * 
* * @author Brian S O'Neill */ @Documented @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.ANNOTATION_TYPE) public @interface ConstraintDefinition { /** * Specify class which will perform constraint checking. Must have a public * constructor with the signature * (Class type, String propertyName, Annotation), * where Annotation refers to the annotation with the * constraint definition. * *

The implementation class need not be explicitly specified. By * default, the constraint class must be a static inner class of the * annotation, named "Constraint". */ // Use void.class to mean default. Class implementation() default void.class; }