public interface AsyncHandlerInterceptor extends HandlerInterceptor
HandlerInterceptor with a callback method invoked after the
start of asynchronous request handling.
When a handler starts an asynchronous request, the DispatcherServlet
exits without invoking postHandle and afterCompletion as it
normally does for a synchronous request, since the result of request handling
(e.g. ModelAndView) is likely not yet ready and will be produced concurrently
from another thread. In such scenarios, afterConcurrentHandlingStarted(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, java.lang.Object)
is invoked instead, allowing implementations to perform tasks such as cleaning
up thread-bound attributes before releasing the thread to the Servlet container.
When asynchronous handling completes, the request is dispatched to the
container for further processing. At this stage the DispatcherServlet
invokes preHandle, postHandle, and afterCompletion.
To distinguish between the initial request and the subsequent dispatch
after asynchronous handling completes, interceptors can check whether the
javax.servlet.DispatcherType of ServletRequest
is "REQUEST" or "ASYNC".
Note that HandlerInterceptor implementations may need to do work
when an async request times out or completes with a network error. For such
cases the Servlet container does not dispatch and therefore the
postHandle and afterCompletion methods will not be invoked.
Instead, interceptors can register to track an asynchronous request through
the registerCallbackInterceptor and registerDeferredResultInterceptor
methods on WebAsyncManager. This can be done proactively on every request from
preHandle regardless of whether async request processing will start.
WebAsyncManager,
CallableProcessingInterceptor,
DeferredResultProcessingInterceptor| Modifier and Type | Method and Description |
|---|---|
default void |
afterConcurrentHandlingStarted(HttpServletRequest request,
HttpServletResponse response,
java.lang.Object handler)
Called instead of
postHandle and afterCompletion
when the handler is being executed concurrently. |
afterCompletion, postHandle, preHandledefault void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, java.lang.Object handler) throws java.lang.Exception
postHandle and afterCompletion
when the handler is being executed concurrently.
Implementations may use the provided request and response but should avoid modifying them in ways that would conflict with the concurrent execution of the handler. A typical use of this method would be to clean up thread-local variables.
request - the current requestresponse - the current responsehandler - the handler (or HandlerMethod) that started async
execution, for type and/or instance examinationjava.lang.Exception - in case of errors