Question

我正在尝试实现长轮询，但是在调用AsyncContext.complete（）之后，我从Weld获得了一个异常：

Warnung:   Error invoking requestDestroyed method on ServletRequestListener org.jboss.weld.servlet.WeldListener
java.lang.NullPointerException
    at org.jboss.weld.context.AbstractBoundContext.deactivate(AbstractBoundContext.java:71)
    at org.jboss.weld.context.http.HttpRequestContextImpl.deactivate(HttpRequestContextImpl.java:70)
    at org.jboss.weld.servlet.WeldListener.requestDestroyed(WeldListener.java:154)
    at org.apache.catalina.core.StandardContext.fireRequestDestroyedEvent(StandardContext.java:5261)
    at org.apache.catalina.core.StandardHostValve.postInvoke(StandardHostValve.java:255)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:359)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
    at java.lang.Thread.run(Thread.java:744)

我的Servlet如下所示：

@WebServlet(urlPatterns = {"/newmsg"}, asyncSupported = true)
public class NewMessageNotifierLongPolling extends HttpServlet {

    private static final Queue<AsyncContext> peers = new ConcurrentLinkedQueue();

    public void notifyClientsAboutNewMessage(@Observes Message msg) {
        for (final AsyncContext ac : peers) {
            try {
                final ServletOutputStream os = ac.getResponse().getOutputStream();
                os.println(msg.getSubject());
                ac.complete();
            } catch (IOException ex) {
                Logger.getLogger(NewMessageNotifierLongPolling.class.getName()).log(Level.SEVERE, null, ex);
            } finally {
                peers.remove(ac);
            }
        }
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType(MediaType.TEXT_PLAIN);
        response.setStatus(202);
        response.setHeader("Pragma", "no-cache");
        response.setCharacterEncoding("UTF-8");
        response.flushBuffer();

        final AsyncContext ac = request.startAsync(request, response);
        ac.setTimeout(35 * 1000);
        ac.addListener(new AsyncListener() {
            @Override
            public void onComplete(AsyncEvent event) throws IOException {
                peers.remove(ac);
            }

            @Override
            public void onTimeout(AsyncEvent event) throws IOException {
                peers.remove(ac);
            }

            @Override
            public void onError(AsyncEvent event) throws IOException {
                peers.remove(ac);
            }

            @Override
            public void onStartAsync(AsyncEvent event) throws IOException {
            }
        });
        peers.add(ac);
    }
}

Answer 1

根据this JIRA，Weld 1.1.10（存在于Tomcat 7.0.23和相关的JBoss服务器中）存在一个错误，导致Async servlet丢失对同一个servlet的请求之间的上下文。

升级Weld或JBoss版本可以解决问题

JEE6 Long Polling WebServlet - 调用AsyncContext＃complete后的异常

1 个答案: