servlet3学习-AsyncContext

Servlet3最大的改变就是支持异步请求的处理

@WebServlet(name = "AsyncServlet", urlPatterns = { "/asyncServlet.do" }, asyncSupported = true, initParams = {                                                                                                              @WebInitParam(name = "threadpoolsize", value = "10"),                                                                                                              @WebInitParam(name = "timeout", value = "10000") })public class AsyncServlet extends HttpServlet {    private static final long serialVersionUID = 6727834393411496060L;    Logger                    logger           = LoggerFactory.getLogger(AsyncServlet.class);    ExecutorService           executorService  = null;    protected void service(HttpServletRequest req, HttpServletResponse resp) {        resp.setCharacterEncoding("GBK");        AsyncContext asyncContext = req.startAsync();        asyncContext.setTimeout(Long.parseLong(getInitParameter("timeout")));        asyncContext.addListener(new AsyncListener() {            @Override            public void onTimeout(AsyncEvent event) throws IOException {                AsyncContext asyncContext = event.getAsyncContext();                logger.error("onTimeout called:" + event.toString());                asyncContext.getResponse().getWriter().write("TIMEOUT");                asyncContext.complete();            }            @Override            public void onStartAsync(AsyncEvent arg0) throws IOException {            }            @Override            public void onError(AsyncEvent event) throws IOException {                AsyncContext asyncContext = event.getAsyncContext();                logger.error("onError called:" + event.toString());                asyncContext.complete();            }            @Override            public void onComplete(AsyncEvent arg0) throws IOException {            }        });        this.enqueLongRunningTask(asyncContext);    }    @Override    public void destroy() {        executorService.shutdown();    }    @Override    public void init() throws ServletException {        int threadpoolsize = Integer.parseInt(getInitParameter("threadpoolsize"));        executorService = Executors.newFixedThreadPool(threadpoolsize);        logger.info("init AsyncServlet");    }    private void enqueLongRunningTask(final AsyncContext asyncContext) {        executorService.execute(new Runnable() {            @Override            public void run() {                try {                    int delay = new Random().nextInt(100);                    Thread.sleep(delay);                    ServletResponse response = asyncContext.getResponse();                    if (response != null) {                        response.getWriter().write(MessageFormat.format("<h1>执行任务了in bgt_id:[{0}], delay:{1}</h1>",                                                                        Thread.currentThread().getId(), delay));                        asyncContext.complete();                    } else {                        throw new IllegalStateException("Response object from context is null!");                    }                } catch (Exception e) {                    log("Problem processing task", e);                    e.printStackTrace();                }            }        });    }}