/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.method.HandlerMethod;
Extends 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 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.
Author: Rossen Stoyanchev See Also: Since: 3.2
/**
* Extends {@code HandlerInterceptor} with a callback method invoked after the
* start of asynchronous request handling.
*
* <p>When a handler starts an asynchronous request, the {@link DispatcherServlet}
* exits without invoking {@code postHandle} and {@code 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, {@link #afterConcurrentHandlingStarted}
* is invoked instead, allowing implementations to perform tasks such as cleaning
* up thread-bound attributes before releasing the thread to the Servlet container.
*
* <p>When asynchronous handling completes, the request is dispatched to the
* container for further processing. At this stage the {@code DispatcherServlet}
* invokes {@code preHandle}, {@code postHandle}, and {@code afterCompletion}.
* To distinguish between the initial request and the subsequent dispatch
* after asynchronous handling completes, interceptors can check whether the
* {@code javax.servlet.DispatcherType} of {@link javax.servlet.ServletRequest}
* is {@code "REQUEST"} or {@code "ASYNC"}.
*
* <p>Note that {@code 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
* {@code postHandle} and {@code afterCompletion} methods will not be invoked.
* Instead, interceptors can register to track an asynchronous request through
* the {@code registerCallbackInterceptor} and {@code registerDeferredResultInterceptor}
* methods on {@link org.springframework.web.context.request.async.WebAsyncManager
* WebAsyncManager}. This can be done proactively on every request from
* {@code preHandle} regardless of whether async request processing will start.
*
* @author Rossen Stoyanchev
* @since 3.2
* @see org.springframework.web.context.request.async.WebAsyncManager
* @see org.springframework.web.context.request.async.CallableProcessingInterceptor
* @see org.springframework.web.context.request.async.DeferredResultProcessingInterceptor
*/
public interface AsyncHandlerInterceptor extends HandlerInterceptor {
Called instead of 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.
Params: - request – the current request
- response – the current response
- handler – the handler (or
HandlerMethod) that started async execution, for type and/or instance examination
Throws: - Exception – in case of errors
/**
* Called instead of {@code postHandle} and {@code afterCompletion}
* when the handler is being executed concurrently.
* <p>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.
* @param request the current request
* @param response the current response
* @param handler the handler (or {@link HandlerMethod}) that started async
* execution, for type and/or instance examination
* @throws Exception in case of errors
*/
default void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response,
Object handler) throws Exception {
}
}