1 /*
2 * Copyright 2002-2012 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.springframework.web.context.request.async;
17
18 import org.springframework.web.context.request.NativeWebRequest;
19
20 /**
21 * Intercepts concurrent request handling, where the concurrent result is
22 * obtained by waiting for a {@link DeferredResult} to be set from a thread
23 * chosen by the application (e.g. in response to some external event).
24 *
25 * <p>A {@code DeferredResultProcessingInterceptor} is invoked before the start
26 * of async processing, after the {@code DeferredResult} is set as well as on
27 * timeout, or or after completing for any reason including a timeout or network
28 * error.
29 *
30 * <p>As a general rule exceptions raised by interceptor methods will cause
31 * async processing to resume by dispatching back to the container and using
32 * the Exception instance as the concurrent result. Such exceptions will then
33 * be processed through the {@code HandlerExceptionResolver} mechanism.
34 *
35 * <p>The {@link #handleTimeout(NativeWebRequest, DeferredResult) afterTimeout}
36 * method can set the {@code DeferredResult} in order to resume processing.
37 *
38 * @author Rossen Stoyanchev
39 * @author Rob Winch
40 * @since 3.2
41 */
42 public interface DeferredResultProcessingInterceptor {
43
44 /**
45 * Invoked immediately before the start of concurrent handling, in the same
46 * thread that started it. This method may be used to capture state just prior
47 * to the start of concurrent processing with the given {@code DeferredResult}.
48 *
49 * @param request the current request
50 * @param deferredResult the DeferredResult for the current request
51 * @throws Exception in case of errors
52 */
53 <T> void beforeConcurrentHandling(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
54
55 /**
56 * Invoked immediately after the start of concurrent handling, in the same
57 * thread that started it. This method may be used to detect the start of
58 * concurrent processing with the given {@code DeferredResult}.
59 *
60 * <p>The {@code DeferredResult} may have already been set, for example at
61 * the time of its creation or by another thread.
62 *
63 * @param request the current request
64 * @param deferredResult the DeferredResult for the current request
65 * @throws Exception in case of errors
66 */
67 <T> void preProcess(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
68
69 /**
70 * Invoked after a {@code DeferredResult} has been set, via
71 * {@link DeferredResult#setResult(Object)} or
72 * {@link DeferredResult#setErrorResult(Object)}, and is also ready to
73 * handle the concurrent result.
74 *
75 * <p>This method may also be invoked after a timeout when the
76 * {@code DeferredResult} was created with a constructor accepting a default
77 * timeout result.
78 *
79 * @param request the current request
80 * @param deferredResult the DeferredResult for the current request
81 * @param concurrentResult the result to which the {@code DeferredResult}
82 * @throws Exception in case of errors
83 */
84 <T> void postProcess(NativeWebRequest request, DeferredResult<T> deferredResult, Object concurrentResult) throws Exception;
85
86 /**
87 * Invoked from a container thread when an async request times out before
88 * the {@code DeferredResult} has been set. Implementations may invoke
89 * {@link DeferredResult#setResult(Object) setResult} or
90 * {@link DeferredResult#setErrorResult(Object) setErrorResult} to resume processing.
91 *
92 * @param request the current request
93 * @param deferredResult the DeferredResult for the current request; if the
94 * {@code DeferredResult} is set, then concurrent processing is resumed and
95 * subsequent interceptors are not invoked
96 * @return {@code true} if processing should continue, or {@code false} if
97 * other interceptors should not be invoked
98 * @throws Exception in case of errors
99 */
100 <T> boolean handleTimeout(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
101
102 /**
103 * Invoked from a container thread when an async request completed for any
104 * reason including timeout and network error. This method is useful for
105 * detecting that a {@code DeferredResult} instance is no longer usable.
106 *
107 * @param request the current request
108 * @param deferredResult the DeferredResult for the current request
109 * @throws Exception in case of errors
110 */
111 <T> void afterCompletion(NativeWebRequest request, DeferredResult<T> deferredResult) throws Exception;
112
113 }