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有时我的 Servlet 以这个异常结束：

    WARNING: StandardWrapperValve[HeartBeatServlet]: PWC1406: Servlet.service() for servlet HeartBeatServlet threw exception
java.lang.IllegalStateException: Not Suspended
    at com.sun.grizzly.tcp.Response.resume(Response.java:768)
    at org.apache.catalina.connector.Request.asyncComplete(Request.java:3993)
    at org.apache.catalina.connector.AsyncContextImpl.complete(AsyncContextImpl.java:242)
    at com.northcane.talkeen.HeartBeatServlet.doPost(HeartBeatServlet.java:47)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:688)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:722)

这是我的 Servlet 的源代码。它唯一要做的就是处理来自 javascript 客户端的长轮询请求，并将 POST 上收到的消息发送给所有这些请求：

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import javax.servlet.AsyncContext;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


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

    private List<AsyncContext> asyncContextList = new LinkedList<>();

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        AsyncContext asyncContext = request.startAsync(request, response);
        asyncContext.setTimeout(30000);
        asyncContextList.add(asyncContext);
    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) {
        String test = request.getParameter("message");
        List<AsyncContext> asyncContexts = new ArrayList<>(asyncContextList);
        asyncContextList.clear();
        for (AsyncContext asyncContext : asyncContexts) {
            ServletResponse res = asyncContext.getResponse();
            res.setContentType("text/html");
            try {
                PrintWriter out = asyncContext.getResponse().getWriter();
                out.println(test + " <br />");
                out.flush();
                asyncContext.complete();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

我做错了什么吗？谢谢

4

1 回答 1

0

（代码有多线程问题。请参阅this SO answer了解如何解决它们。）

该代码将 GET 请求的 AsyncContext 存储在 List 中，并在 POST 上完成 GET 响应。但是由于超时，GET 响应可能已经隐式完成（由 servlet 容器触发）并且存储的 AsyncContext 不会反映这一点。因此，当您检索此存储的 AsyncContext 并尝试完成 GET 请求时，servlet 容器找不到需要恢复的挂起GET 请求。因此出现了 IllegalStateException。

请也参考这个间接回答这个问题的其他答案。

于 2013-05-01T18:11:43.690 回答