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/*
* Copyright 2002-2015 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.context.request.async;
import org.springframework.web.context.request.NativeWebRequest;
/**
* Intercepts concurrent request handling, where the concurrent result is
* obtained by waiting for a {@link DeferredResult} to be set from a thread
* chosen by the application (e.g. in response to some external event).
*
* <p>A {@code DeferredResultProcessingInterceptor} is invoked before the start
* of async processing, after the {@code DeferredResult} is set as well as on
* timeout, or or after completing for any reason including a timeout or network
* error.
*
* <p>As a general rule exceptions raised by interceptor methods will cause
* async processing to resume by dispatching back to the container and using
* the Exception instance as the concurrent result. Such exceptions will then
* be processed through the {@code HandlerExceptionResolver} mechanism.
*
* <p>The {@link #handleTimeout(NativeWebRequest, DeferredResult) afterTimeout}
* method can set the {@code DeferredResult} in order to resume processing.
*
* @author Rossen Stoyanchev
* @author Rob Winch
* @since 3.2
*/
public interface DeferredResultProcessingInterceptor {
/**
* Invoked immediately before the start of concurrent handling, in the same
* thread that started it. This method may be used to capture state just prior
* to the start of concurrent processing with the given {@code DeferredResult}.
* @param request the current request
* @param deferredResult the DeferredResult for the current request
* @throws Exception in case of errors
*/
<T> void beforeConcurrentHandling(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
/**
* Invoked immediately after the start of concurrent handling, in the same
* thread that started it. This method may be used to detect the start of
* concurrent processing with the given {@code DeferredResult}.
* <p>The {@code DeferredResult} may have already been set, for example at
* the time of its creation or by another thread.
* @param request the current request
* @param deferredResult the DeferredResult for the current request
* @throws Exception in case of errors
*/
<T> void preProcess(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
/**
* Invoked after a {@code DeferredResult} has been set, via
* {@link DeferredResult#setResult(Object)} or
* {@link DeferredResult#setErrorResult(Object)}, and is also ready to
* handle the concurrent result.
* <p>This method may also be invoked after a timeout when the
* {@code DeferredResult} was created with a constructor accepting a default
* timeout result.
* @param request the current request
* @param deferredResult the DeferredResult for the current request
* @param concurrentResult the result to which the {@code DeferredResult}
* @throws Exception in case of errors
*/
<T> void postProcess(NativeWebRequest request, DeferredResult<T> deferredResult, Object concurrentResult) throws Exception;
/**
* Invoked from a container thread when an async request times out before
* the {@code DeferredResult} has been set. Implementations may invoke
* {@link DeferredResult#setResult(Object) setResult} or
* {@link DeferredResult#setErrorResult(Object) setErrorResult} to resume processing.
* @param request the current request
* @param deferredResult the DeferredResult for the current request; if the
* {@code DeferredResult} is set, then concurrent processing is resumed and
* subsequent interceptors are not invoked
* @return {@code true} if processing should continue, or {@code false} if
* other interceptors should not be invoked
* @throws Exception in case of errors
*/
<T> boolean handleTimeout(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
/**
* Invoked from a container thread when an async request completed for any
* reason including timeout and network error. This method is useful for
* detecting that a {@code DeferredResult} instance is no longer usable.
* @param request the current request
* @param deferredResult the DeferredResult for the current request
* @throws Exception in case of errors
*/
<T> void afterCompletion(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
}
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