Java 理论与实践: 用JMX检测应用程序

public class TrackingThreadPool extends ThreadPoolExecutor {
　private final Map<Runnable, Boolean> inProgress
= new ConcurrentHashMap<Runnable,Boolean>();
　private final ThreadLocal<Long> startTime = new ThreadLocal<Long>();
　private long totalTime;
　private int totalTasks;
　public TrackingThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime,
　TimeUnit unit, BlockingQueue<Runnable> workQueue) {
　　super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
　}
　protected void beforeExecute(Thread t, Runnable r) {
　　super.beforeExecute(t, r);
　　inProgress.put(r, Boolean.TRUE);
　　startTime.set(new Long(System.currentTimeMillis()));
　}
　protected void afterExecute(Runnable r, Throwable t) {
　　long time = System.currentTimeMillis() - startTime.get().longValue();
　　synchronized (this) {
　　　totalTime += time;
　　　++totalTasks;
　　}
　　inProgress.remove(r);
　　super.afterExecute(r, t);
　}
　public Set<Runnable> getInProgressTasks() {
　　return Collections.unmodifiableSet(inProgress.keySet());
　}
　public synchronized int getTotalTasks() {
　　return totalTasks;
　}
　public synchronized double getAverageTaskTime() {
　　return (totalTasks == 0) ? 0 : totalTime / totalTasks;
　}
}

public class ThreadPoolStatus implements ThreadPoolStatusMBean {
private final TrackingThreadPool pool;
public ThreadPoolStatus(TrackingThreadPool pool) {
　this.pool = pool;
}
public int getActiveThreads() {
　return pool.getPoolSize();
}
public int getActiveTasks() {
　return pool.getActiveCount();
}
public int getTotalTasks() {
　return pool.getTotalTasks();
}
public int getQueuedTasks() {
　return pool.getQueue().size();
}
public double getAverageTaskTime() {
　return pool.getAverageTaskTime();
}
public String[] getActiveTaskNames() {
　return toStringArray(pool.getInProgressTasks());
}
public String[] getQueuedTaskNames() {
　return toStringArray(pool.getQueue());
}
private String[] toStringArray(Collection<Runnable> collection) {
　ArrayList<String> list = new ArrayList<String>();
　for (Runnable r : collection)
　　list.add(r.toString());
　return list.toArray(new String[0]);
}
}