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Groovy example source code file (WithReadLock.java)

This example Groovy source code file (WithReadLock.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

annotation, groovyasttransformationclass, groovyasttransformationclass, string, string, target, target, withreadlock, withreadlock

The Groovy WithReadLock.java source code

 * Copyright 2008-2010 the original author or authors.
 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package groovy.transform;

import org.codehaus.groovy.transform.GroovyASTTransformationClass;

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

 * This annotation is used in conjunction with {@link WithWriteLock} to support read and write synchronization on a method.<br/>
* * To use this annotation, declare {@code @WithReadLock} on your method. The method may be either an instance method or * a static method. The resulting method will allow multiple threads to read the information at the same time. * However, if some other method obtains a write lock, then this method will force callers to wait until the write is complete. <br/>
* * This annotation is a declarative wrapper around the JDK's <code>java.util.concurrent.locks.ReentrantReadWriteLock. * Objects containing this annotation will have a ReentrantReadWriteLock field named <code>$reentrantLock added to the class, * and method access is protected by the lock. If the method is static then the field is static and named <code>$REENTRANTLOCK.

* * The annotation takes an optional parameter for the name of the field. This field must exist on the class and must be * of type ReentrantReadWriteLock. <br/>
* * To understand how this annotation works, it is convenient to think in terms of the source code it replaces. The following * is a typical usage of this annotation from Groovy: * <pre> * import groovy.transform.*; * * public class ResourceProvider { * * private final Map<String, String> data = new HashMap<String, String>(); * * {@code @WithReadLock} * public String getResource(String key) throws Exception { * return data.get(key); * } * * {@code @WithWriteLock} * public void refresh() throws Exception { * //reload the resources into memory * } * } * </pre> * As part of the Groovy compiler, code resembling this is produced: * <pre> * import java.util.concurrent.locks.ReentrantReadWriteLock; * import java.util.concurrent.locks.ReadWriteLock; * * public class ResourceProvider { * * private final ReadWriteLock $reentrantlock = new ReentrantReadWriteLock(); * private final Map<String, String> data = new HashMap<String, String>(); * * public String getResource(String key) throws Exception { * $reentrantlock.readLock().lock(); * try { * return data.get(key); * } finally { * $reentrantlock.readLock().unlock(); * } * } * * public void refresh() throws Exception { * $reentrantlock.writeLock().lock(); * try { * //reload the resources into memory * } finally { * $reentrantlock.writeLock().unlock(); * } * } * } * </pre> * @author Hamlet D'Arcy * @since 1.8.0 */ @java.lang.annotation.Documented @Retention(RetentionPolicy.SOURCE) @Target({ElementType.METHOD}) @GroovyASTTransformationClass("org.codehaus.groovy.transform.ReadWriteLockASTTransformation") public @interface WithReadLock { /** * @return if a user specified lock object with the given name should be used * the lock object must exist. If the annotated method is static then the * lock object must be static. If the annotated method is not static then * the lock object must not be static. */ String value () default ""; }

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