在一个Servlet的同时处理 [英] Simultaneously processing in one Servlet

问题描述

我有一个Servlet其中临危要求，具有处理5个任务（获取数据形式的外部服务器）和所有数据发送回订购的客户。

I have a Servlet which recieves a request, has to process 5 tasks (Grab data Form external Servers) and send all the data back to the client ordered.

如何同时处理5任务，并与该servlet code继续所有5个任务完成后？

How to process the 5 Task simultaneously and continue with the servlet code after all 5 tasks are completed?

推荐答案

您可以使用的 CoundDownLatch

You can use CoundDownLatch

一个同步辅助，允许一个或多个线程等待，直到其他线程中执行一组操作完成。

A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.

样code：

    CountDownLatch startSignal = new CountDownLatch(1);
    CountDownLatch doneSignal = new CountDownLatch(5); // 5 tasks

    class Worker implements Runnable {
        private final CountDownLatch startSignal;
        private final CountDownLatch doneSignal;
        private final int threadNumber;

        // you can pass additional arguments as well
        Worker(CountDownLatch startSignal, CountDownLatch doneSignal,
                                                   int threadNumber) {
            this.startSignal = startSignal;
            this.doneSignal = doneSignal;
            this.threadNumber = threadNumber;
        }

        public void run() {
            try {
                startSignal.await();
                doWork(); // actual work to be performed here    
                doneSignal.countDown();
            } catch (InterruptedException ex) {
                LOGGER.error(ex);
            }
        }
    }

    // 5 new threads are started
    for(int i=1;i<=5;i++){
        new Thread(new Worker(startSignal, doneSignal, i)).start();
    }

    startSignal.countDown(); // let all threads proceed
    try {
        doneSignal.await(); // wait for all to finish
        // all 5 tasks are finished and do whatever you want to do next
    } catch (InterruptedException interruptedException) {
        LOGGER.error(interruptedException);
    }

<一个href=\"http://stackoverflow.com/questions/17827022/what-is-countdown-latch-in-java-multithreading\">Read更多... 和找到更多的例子。 ..

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