线程死亡的监控与回调

//监控线程是否死亡

package io.mycat.bigmem.util;import java.util.ArrayList;import java.util.List;import java.util.concurrent.ConcurrentLinkedQueue;import java.util.concurrent.atomic.AtomicBoolean;/***@desc  监控线程是否死亡,然后执行回调方法.*@author zhangwy   @date 2017年2月21日 上午6:14:34**/public class ThreadDeathWatcher {/*started 线程是否已经启动*/private static AtomicBoolean started = new AtomicBoolean(false);/*需要加入监控,或者不监控的待处理的队列*/private static ConcurrentLinkedQueue<Entry> threadQueue = new ConcurrentLinkedQueue<Entry>();/*正在处理的线程*/private static Thread watchThread = null; /*加入监控*/public static void watche(Thread thread,Runnable task) {if(thread == null) {throw new NullPointerException("thread");}if(task == null) {throw new NullPointerException("task");}if(!thread.isAlive()) {throw new IllegalArgumentException("thread must be alive");}schedual(thread, task, true);} /*移除监控*/public static void unWathe(Thread thread, Runnable task) {if(thread == null) {throw new NullPointerException("thread");}if(task == null) {throw new NullPointerException("task");}schedual(thread, task, false);}/*线程任务的调度*/private static void schedual(Thread thread, Runnable task, boolean isWatching) {Entry entry = new Entry(thread, task, isWatching);threadQueue.add(entry);if(started.compareAndSet(false, true)) {Watcher wathcer = new Watcher();watchThread = new Thread(wathcer, "Deather watcher thread");watchThread.setDaemon(true);watchThread.start();System.out.println(watchThread.getName() + " start   ===========");}}static final class Watcher implements Runnable {List<Entry> watchList = new ArrayList<Entry>();/*监控队列,判断线程是否alive,death则从队列中移除,执行回调,*/@Overridepublic void run() {for(;;) { fetchWatchees();                notifyWatchees();                fetchWatchees();                notifyWatchees();                try {Thread.currentThread().sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}                if(watchList.isEmpty() && threadQueue.isEmpty()) {                started.compareAndSet(true, false);                                if(threadQueue.isEmpty()) {                /*                 * 1.待处理的队列已经为空                 * 2.已经启动了新的线程去处理待处理线程了.*/                break;                }                /*1.已经有了待处理的线程了,需要判断是否已经有新的线程已经启动了,如果没有                 * 当前线程继续处理,否则让新线程去处理.                 * */                if(!started.compareAndSet(false, true)) {                break;                }                }}}/***@desc*@auth zhangwy @date 2017年2月21日 上午7:06:01**/private void fetchWatchees() {for(;;) {Entry entry = threadQueue.poll();if(entry == null) {break;}if(entry.isWatching) {watchList.add(entry);} else {watchList.remove(entry);}}}/***@desc*@auth zhangwy @date 2017年2月21日 上午7:06:04**/private void notifyWatchees() {for(int i = 0; i < watchList.size(); ) {Entry entry = watchList.get(i);if(!entry.thread.isAlive()) {watchList.remove(i);try {entry.task.run();}catch (Exception e) {e.printStackTrace();}} else {i++;}}}}}class Entry {Thread thread ;Runnable task;boolean isWatching;Entry(Thread thread, Runnable task,boolean isWatching) {this.thread = thread;this.task = task;this.isWatching = isWatching;}/*  * @see java.lang.Object#hashCode() */@Overridepublic int hashCode() {return thread.hashCode() ^ task.hashCode();}/*  * @see java.lang.Object#equals(java.lang.Object) */@Overridepublic boolean equals(Object obj) {if(!(this instanceof Entry)) {return false;}if(!(obj instanceof Entry)) {return false;}Entry entry = (Entry)obj;return this.thread == entry.thread && this.task == this.task;}}