001/* 002 * Copyright 2002-2017 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.web.context.request.async; 018 019import org.springframework.web.context.request.NativeWebRequest; 020 021/** 022 * Intercepts concurrent request handling, where the concurrent result is 023 * obtained by waiting for a {@link DeferredResult} to be set from a thread 024 * chosen by the application (e.g. in response to some external event). 025 * 026 * <p>A {@code DeferredResultProcessingInterceptor} is invoked before the start 027 * of async processing, after the {@code DeferredResult} is set as well as on 028 * timeout/error, or after completing for any reason including a timeout or network 029 * error. 030 * 031 * <p>As a general rule exceptions raised by interceptor methods will cause 032 * async processing to resume by dispatching back to the container and using 033 * the Exception instance as the concurrent result. Such exceptions will then 034 * be processed through the {@code HandlerExceptionResolver} mechanism. 035 * 036 * <p>The {@link #handleTimeout(NativeWebRequest, DeferredResult) handleTimeout} 037 * method can set the {@code DeferredResult} in order to resume processing. 038 * 039 * @author Rossen Stoyanchev 040 * @author Rob Winch 041 * @since 3.2 042 */ 043public interface DeferredResultProcessingInterceptor { 044 045 /** 046 * Invoked immediately before the start of concurrent handling, in the same 047 * thread that started it. This method may be used to capture state just prior 048 * to the start of concurrent processing with the given {@code DeferredResult}. 049 * @param request the current request 050 * @param deferredResult the DeferredResult for the current request 051 * @throws Exception in case of errors 052 */ 053 default <T> void beforeConcurrentHandling(NativeWebRequest request, DeferredResult<T> deferredResult) 054 throws Exception { 055 } 056 057 /** 058 * Invoked immediately after the start of concurrent handling, in the same 059 * thread that started it. This method may be used to detect the start of 060 * concurrent processing with the given {@code DeferredResult}. 061 * <p>The {@code DeferredResult} may have already been set, for example at 062 * the time of its creation or by another thread. 063 * @param request the current request 064 * @param deferredResult the DeferredResult for the current request 065 * @throws Exception in case of errors 066 */ 067 default <T> void preProcess(NativeWebRequest request, DeferredResult<T> deferredResult) 068 throws Exception { 069 } 070 071 /** 072 * Invoked after a {@code DeferredResult} has been set, via 073 * {@link DeferredResult#setResult(Object)} or 074 * {@link DeferredResult#setErrorResult(Object)}, and is also ready to 075 * handle the concurrent result. 076 * <p>This method may also be invoked after a timeout when the 077 * {@code DeferredResult} was created with a constructor accepting a default 078 * timeout result. 079 * @param request the current request 080 * @param deferredResult the DeferredResult for the current request 081 * @param concurrentResult the result to which the {@code DeferredResult} 082 * @throws Exception in case of errors 083 */ 084 default <T> void postProcess(NativeWebRequest request, DeferredResult<T> deferredResult, 085 Object concurrentResult) throws Exception { 086 } 087 088 /** 089 * Invoked from a container thread when an async request times out before 090 * the {@code DeferredResult} has been set. Implementations may invoke 091 * {@link DeferredResult#setResult(Object) setResult} or 092 * {@link DeferredResult#setErrorResult(Object) setErrorResult} to resume processing. 093 * @param request the current request 094 * @param deferredResult the DeferredResult for the current request; if the 095 * {@code DeferredResult} is set, then concurrent processing is resumed and 096 * subsequent interceptors are not invoked 097 * @return {@code true} if processing should continue, or {@code false} if 098 * other interceptors should not be invoked 099 * @throws Exception in case of errors 100 */ 101 default <T> boolean handleTimeout(NativeWebRequest request, DeferredResult<T> deferredResult) 102 throws Exception { 103 104 return true; 105 } 106 107 /** 108 * Invoked from a container thread when an error occurred while processing an async request 109 * before the {@code DeferredResult} has been set. Implementations may invoke 110 * {@link DeferredResult#setResult(Object) setResult} or 111 * {@link DeferredResult#setErrorResult(Object) setErrorResult} to resume processing. 112 * @param request the current request 113 * @param deferredResult the DeferredResult for the current request; if the 114 * {@code DeferredResult} is set, then concurrent processing is resumed and 115 * subsequent interceptors are not invoked 116 * @param t the error that occurred while request processing 117 * @return {@code true} if error handling should continue, or {@code false} if 118 * other interceptors should by bypassed and not be invoked 119 * @throws Exception in case of errors 120 */ 121 default <T> boolean handleError(NativeWebRequest request, DeferredResult<T> deferredResult, 122 Throwable t) throws Exception { 123 124 return true; 125 } 126 127 /** 128 * Invoked from a container thread when an async request completed for any 129 * reason including timeout and network error. This method is useful for 130 * detecting that a {@code DeferredResult} instance is no longer usable. 131 * @param request the current request 132 * @param deferredResult the DeferredResult for the current request 133 * @throws Exception in case of errors 134 */ 135 default <T> void afterCompletion(NativeWebRequest request, DeferredResult<T> deferredResult) 136 throws Exception { 137 } 138 139}