Requires.java

/**
 * Copyright (c) 2013, Andre Steingress
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1.) Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * disclaimer.
 * 2.) Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided with the distribution.
 * 3.) Neither the name of Andre Steingress nor the names of its contributors may be used to endorse or
 * promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.gcontracts.annotations;

import org.gcontracts.annotations.meta.AnnotationProcessorImplementation;
import org.gcontracts.annotations.meta.Precondition;
import org.gcontracts.common.impl.RequiresAnnotationProcessor;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


/**
 * <p>
 * Represents a <b>method precondition</b>.
 * </p>
 * <p>
 * A precondition is a condition that must be met by clients of this class. Whenever the
 * precondition can be satisfied, it is guaranteed that the supplier will fullfil the method's
 * postcondition.
 * </p>
 * <p>
 * A method's precondition is executed <i>as the first statement</i> within a method call. A
 * successor's precondition weakens the precondition of its parent class, e.g. if A.someMethod
 * declares a precondition and B.someMethod overrides the method the preconditions are combined with a boolean OR.
 * </p>
 * <p>
 * Example:
 *
 * <pre>
 *   @Requires({ argument1 != argument2 && argument2 >= 0 })
 *   void someOperation(def argument1, def argument2)  {
 *     ...
 *   }
 * </pre>
 * </p>
 *
 * @author ast
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})

@Precondition
@AnnotationProcessorImplementation(RequiresAnnotationProcessor.class)
public @interface Requires {
    Class value();
}