java - 为什么在同步线程时 WebMethods 会被阻塞？

Question

请查看我的 JAX-WS Web 服务代码示例:

@WebService
public class ClassA {

@WebMethod
public synchronized void doSomething() {
    new Thread(new Runnable() { // Thread X
        @Override
        public void run() {
            synchronized (ClassA.this) {
                // Do something which should be run in this separate
                // thread, but not twice at the same time
                try {
                    System.out.println("Thread X Start");
                    Thread.sleep(10000);
                    System.out.println("Thread X End");
                } catch (InterruptedException e) {
                }
            }
        }
    }).start();
}

如果 WebMethod 被调用两次，第二次调用正在等待线程 X 完成 - 为什么？

Answer 1

问题是你已经同步了 doSomething。这绝对应该被删除，因为它会阻止您的 web 服务中的多线程。对于内部同步块(synchronized block)，我也会将其删除并尝试使用 single-Thread ThreadPool以便一次执行一个作业。

    // Initiate you thread pool and make sure it is unique
    ExecutorService service = Executors.newFixedThreadPool(1);

    ...
    // In your web method:
    Future<?> futureResult = service.submit(new Runnable()/or new Callable());
    // Using callable, you will get a Typed Future

    Object result = futureResult.get();// If you need to wait for the result of the runnable/callable.
    ...

自 Java 1.5 起可用