java - 从HttpServletRequest获取AsyncContext

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

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 {

        }
    });
}

因此isAsyncDispatch按预期返回true。但是，当我尝试getAsyncContext时，它失败，但出现以下异常:

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

实际上，request.isAsyncStarted()返回false，但是request.isAsyncSupported()为true，request.getDispatcherType()为ASYNC。

我不明白:它是否异步？也许我使用API​​的方式错误？如何添加AsyncListener？也许是因为我使用的是Tomcat？

先感谢您!

最佳答案

当我过去完成此操作时，我们已完成:

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

getAsyncContext()的Javadoc确实声明:(在ServletRequest中)

IllegalStateException-如果此请求尚未进入异步模式，即，既未调用startAsync()也未调用startAsync(ServletRequest，ServletResponse)