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厉害了，Servlet3的异步处理机制

Servlet3发布好几年了，又有多少人知道它的新特性呢？下面简单介绍下。

主要增加了以下特性：

1、异步处理支持

2、可插性支持

3、注解支持，零配置，可不用配置web.xml

...

异步处理是什么鬼？

直接操起键盘干。

@WebServlet(name = "index", urlPatterns = { "/" }, asyncSupported = true)

public class IndexServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        resp.setContentType("text/html");

        try {

            PrintWriter out = resp.getWriter();

            out.println("servlet started.<br/>");

            out.flush();

            AsyncContext asyncContext = req.startAsync();

            asyncContext.addListener(getListener());

            asyncContext.start(new IndexThread(asyncContext));

            out.println("servlet end.<br/>");

            out.flush();

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

    /**

     * 异步线程结果监听

     * @author javastack

     * @return

     */

    private AsyncListener getListener() {

        return new AsyncListener() {

            public void onComplete(AsyncEvent asyncEvent) throws IOException {

                asyncEvent.getSuppliedResponse().getWriter().close();

                System.out.println("thread completed.");

            }

            public void onError(AsyncEvent asyncEvent) throws IOException {

                System.out.println("thread error.");

            }

            public void onStartAsync(AsyncEvent asyncEvent) throws IOException {

                System.out.println("thread started.");

            }

            public void onTimeout(AsyncEvent asyncEvent) throws IOException {

                System.out.println("thread timeout.");

            }

        };

    }

}

public class IndexThread implements Runnable {

    private AsyncContext asyncContext;

    public IndexThread(AsyncContext asyncContext) {

        this.asyncContext = asyncContext;

    }

    public void run() {

        try {

            Thread.sleep(5000);

            PrintWriter out = asyncContext.getResponse().getWriter();

            out.println("hello servlet3.<br/>");

            out.flush();

            asyncContext.complete();

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}

访问localhost:8080/test

页面首先输出