Question

我有以下Async Servlet，对应的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（）]对于具有异步状态的请求无效[COMPLETING]

不确定此代码中的错误

根据servlet3.0规范，我们可以将AsyncListeners添加到获取的AsyncContext 它将能够听取各种事件。在我的情况下，应该监听onComplete()，并且应该将请求发送到jsp13.jsp视图（我的网络应用上下文中有jsp13.jsp）

我使用的是最新版本的tomcat 7.0.x和servlet 3.0规范

Answer 1

嗯，这不会起作用。您已完成申请，无法再次发送。 complete（）结束你的周期，响应已经发送。

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

1 个答案: