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我正在阅读有关“Servlet 3.0 中的异步处理支持”的专家（？）教程（http://www.javaworld.com/javaworld/jw-02-2009/jw-02-servlet3.html?page=2） . 其中有以下代码片段：

@WebServlet(name="myServlet", urlPatterns={"/slowprocess"}, asyncSupported=true)
public class MyServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        AsyncContext aCtx = request.startAsync(request, response);
        ServletContext appScope = request.getServletContext();
        ((Queue<AsyncContext>)appScope.getAttribute("slowWebServiceJobQueue")).add(aCtx);
    }
}

@WebServletContextListener
public class SlowWebService implements ServletContextListener {

    public void contextInitialized(ServletContextEvent sce) {
        Queue<AsyncContext> jobQueue = new ConcurrentLinkedQueue<AsyncContext>();
        sce.getServletContext().setAttribute("slowWebServiceJobQueue", jobQueue);
        // pool size matching Web services capacity
        Executor executor = Executors.newFixedThreadPool(10);
        while(true)
        {
            if(!jobQueue.isEmpty())
            {
                final AsyncContext aCtx = jobQueue.poll();
                executor.execute(new Runnable(){
                    public void run() {
                        ServletRequest request = aCtx.getRequest();
                        // get parameteres
                        // invoke a Web service endpoint
                        // set results
                        aCtx.forward("/result.jsp");
                    }
                });
            }
        }
    }

    public void contextDestroyed(ServletContextEvent sce) {
    }

}

因为，这是一篇专家“这是如何完成的”文章，我假设他们不会编写一些愚蠢的代码。但我无法接受在“contextInitialized()”中有一个“while(true)”循环。

  1. 据我了解，此上下文侦听器线程永远不会退出“contextInitialized()”方法。对 ？
  2. 我的应用程序中的任何其他 Servlet 会发生什么情况？他们可以免费服务请求吗？或者这是否会降低整个 servlet 容器？
4

1 回答 1

2

1）我会改变代码如下：

@WebServletContextListener
public class SlowWebService implements ServletContextListener, Runnable {
    private volatile boolean running;
    ExecutorService executor;
    Thread runner;
    Queue<AsyncContext> jobQueue;

    public void contextInitialized(ServletContextEvent sce) {
        jobQueue = new ConcurrentLinkedQueue<AsyncContext>();
        sce.getServletContext().setAttribute("slowWebServiceJobQueue", jobQueue);
        // pool size matching Web services capacity
        executor = Executors.newFixedThreadPool(10);
        runner = new Thread(this);
        runner.start();
    }

    public void run() {
        running = true;
        while(running)
        {
            try {
                if(!jobQueue.isEmpty())
                {
                    final AsyncContext aCtx = jobQueue.poll();
                    executor.execute(new Runnable(){
                        public void run() {
                            ServletRequest request = aCtx.getRequest();
                            // get parameteres
                            // invoke a Web service endpoint
                            // set results
                            aCtx.forward("/result.jsp");
                        }
                    });
                }
            }
            catch (InterruptException e) {
            }
        }
    }

    public void contextDestroyed(ServletContextEvent sce) {
        running = false;
        runner.interrupt();
        executor.shutdown();
    }
}

2) 其他 Servlet 不应该受到影响，只要它们具有不同的 urlPattern。

于 2013-03-27T19:23:49.623 回答