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/*
* Copyright 2006-2012 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.
*
* <p>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.
* <p>
* Example integer constraint:
* <pre>
* @Documented
* <b>@Retention(RetentionPolicy.RUNTIME)</b>
* <b>@Target(ElementType.METHOD)</b>
* <b>@ConstraintDefinition</b>
* 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);
* }
* }
* }
* }
* </pre>
*
* The newly defined integer constraint can be applied to property mutators.
*
* <pre>
* public interface UserInfo extends Storable {
* ...
*
* int getAge();
* // Constraint is called before setting age.
* <b>@IntegerConstraint(min=0, max=120)</b>
* void setAge(int value);
* }
* </pre>
*
* @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
* <code>(Class type, String propertyName, <i>Annotation</i>)</code>,
* where <code><i>Annotation</i></code> refers to the annotation with the
* constraint definition.
*
* <p>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;
}
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