groovy.transform.WithReadLock Maven / Gradle / Ivy
/*
* Copyright 2008-2013 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,
* 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 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.
*
* 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.
*
* This annotation is a declarative wrapper around the JDK's java.util.concurrent.locks.ReentrantReadWriteLock.
* Objects containing this annotation will have a ReentrantReadWriteLock field named $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 $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.
*
* 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:
*
* 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
* }
* }
*
* As part of the Groovy compiler, code resembling this is produced:
*
* 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();
* }
* }
* }
*
*
* @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 "";
}