Spring Async DeferredResult在Tomcat 8中不起作用

描述的是关系到Tomcat的一个bug这个问题在这里，这里和这里。

可能的解决方案：

1. 使用更稳定的Tomcat版本，例如Tomcat 7.0.47，该错误已得到修复。
2. 使用更高级的调度程序，例如org.springframework.web.servlet.DispatcherServlet
3. 按照此处的建议覆盖HttpServlet ：

   public class AsyncServlet extends HttpServlet {protected void doGet(final HttpServletRequest request, HttpServletResponse response)        throws ServletException, IOException {    if (request.isAsyncStarted()) {        response.getWriter().write("asyncResult=" + request.getAttribute("asyncResult"));    } else {        final AsyncContext asyncContext = request.startAsync(request, response);        asyncContext.addListener(new AsyncListener() { public void onTimeout(AsyncEvent event) throws IOException {     request.setAttribute("asyncResult", "timeoutn");     asyncContext.dispatch(); } public void onStartAsync(AsyncEvent event) throws IOException { } public void onError(AsyncEvent event) throws IOException { } public void onComplete(AsyncEvent event) throws IOException { }        });        asyncContext.setTimeout(5000L);    }}

   }