hunt.stomp.support.ChannelInterceptor source code

1 /*
2  * Copyright 2002-2018 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 
17 module hunt.stomp.support.ChannelInterceptor;
18 
19 import hunt.stomp.Message;
20 import hunt.stomp.MessageChannel;
21 
22 /**
23  * Interface for interceptors that are able to view and/or modify the
24  * {@link Message Messages} being sent-to and/or received-from a
25  * {@link MessageChannel}.
26  *
27  * @author Mark Fisher
28  * @author Rossen Stoyanchev
29  * @since 4.0
30  * @see Message
31  * @see MessageChannel
32  */
33 abstract class ChannelInterceptor {
34 
35 	/**
36 	 * Invoked before the Message is actually sent to the channel.
37 	 * This allows for modification of the Message if necessary.
38 	 * If this method returns {@code null} then the actual
39 	 * send invocation will not occur.
40 	 */
41 	
42 	MessageBase preSend(MessageBase message, MessageChannel channel) {
43 		return message;
44 	}
45 
46 	/**
47 	 * Invoked immediately after the send invocation. The 
48 	 * value argument represents the return value of that invocation.
49 	 */
50 	void postSend(MessageBase message, MessageChannel channel, bool sent) {
51 	}
52 
53 	/**
54 	 * Invoked after the completion of a send regardless of any exception that
55 	 * have been raised thus allowing for proper resource cleanup.
56 	 * <p>Note that this will be invoked only if {@link #preSend} successfully
57 	 * completed and returned a Message, i.e. it did not return {@code null}.
58 	 * @since 4.1
59 	 */
60 	void afterSendCompletion(
61 			MessageBase message, MessageChannel channel, bool sent, Exception ex) {
62 	}
63 
64 	/**
65 	 * Invoked as soon as receive is called and before a Message is
66 	 * actually retrieved. If the return value is 'false', then no
67 	 * Message will be retrieved. This only applies to PollableChannels.
68 	 */
69 	bool preReceive(MessageChannel channel) {
70 		return true;
71 	}
72 
73 	/**
74 	 * Invoked immediately after a Message has been retrieved but before
75 	 * it is returned to the caller. The Message may be modified if
76 	 * necessary; {@code null} aborts further interceptor invocations.
77 	 * This only applies to PollableChannels.
78 	 */
79 	
80 	MessageBase postReceive(MessageBase message, MessageChannel channel) {
81 		return message;
82 	}
83 
84 	/**
85 	 * Invoked after the completion of a receive regardless of any exception that
86 	 * have been raised thus allowing for proper resource cleanup.
87 	 * <p>Note that this will be invoked only if {@link #preReceive} successfully
88 	 * completed and returned {@code true}.
89 	 * @since 4.1
90 	 */
91 	void afterReceiveCompletion(MessageBase message, MessageChannel channel,
92 			Exception ex) {
93 	}
94 
95 }