IllegalStateException:不支持 AsyncContext.startAsync(req, res) [英] IllegalStateException: Not supported on AsyncContext.startAsync(req, res)

问题描述

我创建了一个 servlet 3.0 来探索异步请求处理:

I have created a servlet 3.0 to explore asynchronous request processing:

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

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, IOException {

        AsyncContext tmp = req.startAsync(req, res);
        ...

    }    

}

但是当 .startAsync(...) 被调用时，我得到一个 IllegalStateException.我知道 Javadoc 提到了该异常，但我确实明确启用了异步(参见 WebServlet 注释).我使用的是随 NetBeans 一起提供的 Tomcat 7.0.11.0.

but I get an IllegalStateException when .startAsync(...) is called. I know the Javadoc mentions that exception, but I did explicitly enable async (c.f. WebServlet annotation). I am using Tomcat 7.0.11.0 delivered with NetBeans.

我可以确认 req.isAsyncSupported() 返回 false.我究竟做错了什么?我还需要做什么才能启用异步处理?

I could confirm that req.isAsyncSupported() is returning false. What am I doing wrong? What more do I need to do to enable async processing?

我尝试实现以下 example 并遇到了同样的问题.

I tried to implement the following example and got the same issue.

推荐答案

我查看了 Tomcat 的代码，发现 asyncSupported 变量必须显式设置为 true.这就是为什么你得到 req.isAsyncSupported() == false.

I checked out Tomcat's code and saw that the asyncSupported variable has to be explicitly set to true. That's why you are getting req.isAsyncSupported() == false.

您可以尝试通过以下方法之一将 HttpServletRequest 对象中的 async 属性设置为 true.

You could try to set the async attribute in the HttpServletRequest object to true by one of the following methods.

req.setAttribute("org.apache.catalina.ASYNC_SUPPORTED", true);

或

((org.apache.catalina.connector.Request)req).setAsyncSupported(true);

希望有帮助.

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