从HttpServletRequest获取AsyncContext [英] Get AsyncContext from HttpServletRequest

问题描述

我正在使用Spring的 OncePerRequestFilter 覆盖 shouldNotFilterAsyncDispatch 方法返回false。这样它就可以处理异步请求。在过滤器中我尝试执行以下操作：

I'm using Spring's OncePerRequestFilter overriding shouldNotFilterAsyncDispatch method to return false. This way it can handle asynchronous requests. In the filter I'm trying to do the following:

if (isAsyncDispatch(request)) {
    request.getAsyncContext().addListener(new AsyncListener() {
        @Override
        public void onComplete(AsyncEvent event) throws IOException {
            System.out.println("onComplete");
        }

        @Override
        public void onTimeout(AsyncEvent event) throws IOException {

        }

        @Override
        public void onError(AsyncEvent event) throws IOException {
            System.out.println("onError");
        }

        @Override
        public void onStartAsync(AsyncEvent event) throws IOException {

        }
    });
}

所以 isAsyncDispatch 返回如预期的那样。但是当我尝试 getAsyncContext 时，它失败并出现以下异常：

So isAsyncDispatch returns true as expected. But when I try getAsyncContext it fails with the following exception:

IllegalStateException: It is illegal to call this method if the current request is not in asynchronous mode (i.e. isAsyncStarted() returns false)

确实， request.isAsyncStarted（）返回false，但 request.isAsyncSupported（）为true且 request.getDispatcherType（）是 ASYNC 。

Indeed, request.isAsyncStarted() returns false, but request.isAsyncSupported() is true and request.getDispatcherType() is ASYNC.

我不明白：是不同步？也许我以错误的方式使用API​​？如何添加 AsyncListener ？也许是因为我正在使用Tomcat？

I don't get: is it async or not? Maybe I'm using the API in a wrong way? How do I add an AsyncListener? Maybe it is because I'm using Tomcat?

提前谢谢你！

推荐答案

当我在过去做过这个时，我们已经完成了：

When I have done this in the past, we have done:

if (request.isAsyncSupported()) {
      AsyncContext asyncContext = request.startAsync();
      // Do whatever with context
}

<$ c的javadoc $ c> getAsyncContext（）确实状态:(在 ServletRequest ）

IllegalStateException - 如果此请求尚未进入异步模式，即，如果既没有调用startAsync（）也没有调用startAsync（ServletRequest，ServletResponse）

IllegalStateException - if this request has not been put into asynchronous mode, i.e., if neither startAsync() nor startAsync(ServletRequest,ServletResponse) has been called

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