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Diffstat (limited to 'simple/simple-common/src/main/java/org/simpleframework/common/thread/Daemon.java')
-rw-r--r-- | simple/simple-common/src/main/java/org/simpleframework/common/thread/Daemon.java | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/simple/simple-common/src/main/java/org/simpleframework/common/thread/Daemon.java b/simple/simple-common/src/main/java/org/simpleframework/common/thread/Daemon.java new file mode 100644 index 0000000..3b7b5bf --- /dev/null +++ b/simple/simple-common/src/main/java/org/simpleframework/common/thread/Daemon.java @@ -0,0 +1,164 @@ +/* + * Daemon.java February 2009 + * + * Copyright (C) 2009, Niall Gallagher <niallg@users.sf.net> + * + * 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 org.simpleframework.common.thread; + +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.concurrent.atomic.AtomicReference; + +/** + * The <code>Daemon</code> object provides a named thread which will + * execute the <code>run</code> method when started. This offers + * some convenience in that it hides the normal thread methods and + * also allows the object extending this to provide the name of the + * internal thread, which is given an incrementing sequence number + * appended to the name provided. + * + * @author Niall Gallagher + */ +public abstract class Daemon implements Runnable { + + /** + * This is the current thread executing this service. + */ + private final AtomicReference<Thread> reference; + + /** + * This is the internal thread used by this daemon instance. + */ + private final DaemonFactory factory; + + /** + * This is used to determine if the daemon is active. + */ + private final AtomicBoolean active; + + /** + * This is the internal thread that is executed by this. + */ + private final Runnable delegate; + + /** + * Constructor for the <code>Daemon</code> object. This will + * create the internal thread and ensure it is a daemon. When it + * is started the name of the internal thread is set using the + * name of the instance as taken from <code>getName</code>. If + * the name provided is null then no name is set for the thread. + */ + protected Daemon() { + this.reference = new AtomicReference<Thread>(); + this.delegate = new RunnableDelegate(this); + this.factory = new DaemonFactory(); + this.active = new AtomicBoolean(); + } + + /** + * This is used to determine if the runner is active. If it is not + * active then it is assumed that no thread is executing. Also, if + * this is extended then any executing thread to stop as soon as + * this method returns false. + * + * @return this returns true if the runner is active + */ + public boolean isActive() { + return active.get(); + } + + /** + * This is used to start the internal thread. Once started the + * internal thread will execute the <code>run</code> method of + * this instance. Aside from starting the thread this will also + * ensure the internal thread has a unique name. + */ + public void start() { + Class type = getClass(); + + if (!active.get()) { + Thread thread = factory.newThread(delegate, type); + + reference.set(thread); + active.set(true); + thread.start(); + } + } + + /** + * This is used to interrupt the internal thread. This is used + * when there is a need to wake the thread from a sleeping or + * waiting state so that some other operation can be performed. + * Typically this is required when killing the thread. + */ + public void interrupt() { + Thread thread = reference.get(); + + if(thread != null) { + thread.interrupt(); + } + } + + /** + * This method is used to stop the thread without forcing it to + * stop. It acts as a means to deactivate it. It is up to the + * implementor to ensure that the <code>isActive</code> method + * is checked to determine whether it should continue to run. + */ + public void stop() { + active.set(false); + } + + /** + * The <code>RunnableDelegate</code> object is used to actually + * invoke the <code>run</code> method. A delegate is used to ensure + * that once the task has finished it is inactive so that it can + * be started again with a new thread. + */ + private class RunnableDelegate implements Runnable { + + /** + * This is the runnable that is to be executed. + */ + private final Runnable task; + + /** + * Constructor for the <code>RunnableDelegate</code> object. The + * delegate requires the actual runnable that is to be executed. + * As soon as the task has finished the runner becomes inactive. + * + * @param task this is the task to be executed + */ + public RunnableDelegate(Runnable task) { + this.task = task; + } + + /** + * This is used to execute the task. Once the task has finished + * the runner becomes inactive and any reference to the internal + * thread is set to null. This ensures the runner can be started + * again at a later time if desired. + */ + public void run() { + try { + task.run(); + } finally { + reference.set(null); + active.set(false); + } + } + + } +} |