GuardedBy.java

/*
 * ====================================================================
 *
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package com.apigee.sdk.apm.http.annotation;

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

/**
 * The field or method to which this annotation is applied can only be accessed
 * when holding a particular lock, which may be a built-in (synchronization)
 * lock, or may be an explicit java.util.concurrent.Lock.
 * 
 * The argument determines which lock guards the annotated field or method:
 * <ul>
 * <li>
 * <code>this</code> : The intrinsic lock of the object in whose class the field
 * is defined.</li>
 * <li>
 * <code>class-name.this</code> : For inner classes, it may be necessary to
 * disambiguate 'this'; the <em>class-name.this</em> designation allows you to
 * specify which 'this' reference is intended</li>
 * <li>
 * <code>itself</code> : For reference fields only; the object to which the
 * field refers.</li>
 * <li>
 * <code>field-name</code> : The lock object is referenced by the (instance or
 * static) field specified by <em>field-name</em>.</li>
 * <li>
 * <code>class-name.field-name</code> : The lock object is reference by the
 * static field specified by <em>class-name.field-name</em>.</li>
 * <li>
 * <code>method-name()</code> : The lock object is returned by calling the named
 * nil-ary method.</li>
 * <li>
 * <code>class-name.class</code> : The Class object for the specified class
 * should be used as the lock object.</li>
 * <p>
 * Based on code developed by Brian Goetz and Tim Peierls and concepts published
 * in 'Java Concurrency in Practice' by Brian Goetz, Tim Peierls, Joshua Bloch,
 * Joseph Bowbeer, David Holmes and Doug Lea.
 */
@Documented
@Target({ ElementType.FIELD, ElementType.METHOD })
@Retention(RetentionPolicy.CLASS)
// The original version used RUNTIME
public @interface GuardedBy {
	String value();
}