java.lang.IllegalStateException：调用 [asyncDispatch()] 对具有异步状态 [COMPLETING] 的请求无效

Question

我有以下 Async Servlet、相应的 Listener 和 AsyncProcessor 类

AsyncProcessor.java：

public class AsyncProcessor implements Runnable {

    private AsyncContext asyncContext;

    public AsyncProcessor(AsyncContext asyncContext, String view) {
        this.asyncContext = asyncContext;
        this.asyncContext.getRequest().setAttribute("dispatch", view);
    }

    public void run() {
        try {
            Thread.sleep(10*1000);
            asyncContext.complete();
        } catch(Exception e) {
        }
    }

}

MyServlet13.java：

@WebServlet(name="myServlet13", urlPatterns="/servlet13", asyncSupported=true)
public class MyServlet13 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        AsyncContext asyncContext = request.startAsync();
        System.out.println("Before starting Async processing");
        asyncContext.addListener(new MyAsyncListener());
        Executor executor = (Executor)getServletContext().getAttribute("executor");
        asyncContext.start(new AsyncProcessor(asyncContext, "/jsp13.jsp"));
        System.out.println("After starting Async processing");
    }

}

MyAsyncListener.java：

public class MyAsyncListener implements AsyncListener {

    public void onStartAsync(AsyncEvent asyncEvent) throws IOException {
        System.out.println("This is from onStartAsync");
    }

    public void onComplete(AsyncEvent asyncEvent) throws IOException {
        System.out.println("This is from onComplete, before dispatch");
        AsyncContext asyncContext = asyncEvent.getAsyncContext();
        asyncContext.dispatch("/jsp13.jsp");
        asyncContext.getResponse().getWriter().println("Async tasks completed...<br>");
        System.out.println("This is from onComplete, after dispatch");
    }

    public void onTimeout(AsyncEvent asyncEvent) throws IOException {
        System.out.println("This is from onTimeout");
    }

    public void onError(AsyncEvent asyncEvent) throws IOException {
        System.out.println("This is from onError");
    }

}

当我尝试使用 /servlet13 url 模式调用 MyServlet13 时，我得到以下异常

java.lang.IllegalStateException : 调用 [asyncDispatch()] 对具有异步状态 [COMPLETING] 的请求无效

不知道这段代码有什么问题

根据 servlet3.0 规范，我们可以将 AsyncListeners 添加到获得的AsyncContext 它将能够监听各种事件。在我的例子中，onComplete() 应该被监听，并且请求应该被发送到 jsp13.jsp 视图（我的网络应用上下文中确实有 jsp13.jsp）

我正在使用最新版本的 tomcat 7.0.x 和 servlet 3.0 规范

Answer 1

好吧，这行不通。您已经完成了您的请求，您不能再次发送它。 complete() 结束你的循环，响应已经发送。