Java 线程池中worker

Java 线程池中worker

在java线程中,真正执行计算操作的内容是在一个worker类中。

Worker的主要代码:

    private final class Worker
        extends AbstractQueuedSynchronizer
        implements Runnable
    {
        /**
         * This class will never be serialized, but we provide a
         * serialVersionUID to suppress a javac warning.
         */
        private static final long serialVersionUID = 6138294804551838833L;

        /** Thread this worker is running in.  Null if factory fails. */
        final Thread thread;
        /** Initial task to run.  Possibly null. */
        Runnable firstTask;
        /** Per-thread task counter */
        volatile long completedTasks;

        /**
         * Creates with given first task and thread from ThreadFactory.
         * @param firstTask the first task (null if none)
         */
        Worker(Runnable firstTask) {
            setState(-1); // inhibit interrupts until runWorker
            this.firstTask = firstTask;
            this.thread = getThreadFactory().newThread(this);
        }

        /** Delegates main run loop to outer runWorker  */
        public void run() {
            runWorker(this);
        }
        ......

总体来看,worker其实就是一个Runable,其也是需要构造成一个Thread对象,然后调用Thread start方法运行的。只不过在worker的run方法中是定一个了一个runWoker的方法。这个方法的主要内容从 for 循环的不停的从task队列中获取对应的runable的task,然后同步调用这个task的run()方法。其实就是在某个线程中,不停的拿队列中的任务进行执行。

运行worker

可以看到构造方法内,有一个Thread对象,其使用了ThreadFactory构造了一个新的线程,并且线程的runable是worker本身。

     this.thread = getThreadFactory().newThread(this);

所以需要执行worker的时候,只需要调用worker中的thread的start方法即可,并且可以调用thread的方法来控制worker的状态:

interrupt等。

worker和ThreadPool

在ThreadPool中是有一个workder集合的。通过这个集合,我们可以知道有多少worker线程在进行工作等,每一个worker都是各自进行工作,工作的内容就是不停的获取task,然后执行task即可。

worker中的异常处理

 try {
            while (task != null || (task = getTask()) != null) {
                w.lock();
                // If pool is stopping, ensure thread is interrupted;
                // if not, ensure thread is not interrupted.  This
                // requires a recheck in second case to deal with
                // shutdownNow race while clearing interrupt
                if ((runStateAtLeast(ctl.get(), STOP) ||
                     (Thread.interrupted() &&
                      runStateAtLeast(ctl.get(), STOP))) &&
                    !wt.isInterrupted())
                    wt.interrupt();
                try {
                    beforeExecute(wt, task);
                    Throwable thrown = null;
                    try {
                        task.run();
                    } catch (RuntimeException x) {
                        thrown = x; throw x;
                    } catch (Error x) {
                        thrown = x; throw x;
                    } catch (Throwable x) {
                        thrown = x; throw new Error(x);
                    } finally {
                        afterExecute(task, thrown);
                    }
                } finally {
                    task = null;
                    w.completedTasks++;
                    w.unlock();
                }
            }
            completedAbruptly = false;
        } finally {
            processWorkerExit(w, completedAbruptly);
        }

通过源代码可以看出,对应的Exception都是保存在thrownn中,在finally中交给了 afterExecute进行了处理。
所以可以自己实现对应的afterExecute来进行处理系统内部发生的异常问题。

你可能感兴趣的:(Java 线程池中worker)