1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.handler.chain;
21
22 import org.apache.mina.core.session.IoSession;
23
24 /**
25 * <p>A {@link IoHandlerCommand} encapsulates a unit of processing work to be
26 * performed, whose purpose is to examine and/or modify the state of a
27 * transaction that is represented by custom attributes provided by
28 * {@link IoSession}. Individual {@link IoHandlerCommand}s can be assembled into
29 * a {@link IoHandlerChain}, which allows them to either complete the
30 * required processing or delegate further processing to the next
31 * {@link IoHandlerCommand} in the {@link IoHandlerChain}.</p>
32 *
33 * <p>{@link IoHandlerCommand} implementations typically retrieve and store state
34 * information in the {@link IoSession} that is passed as a parameter to
35 * the {@link #execute(NextCommand,IoSession,Object)} method, using custom
36 * session attributes. If you think getting attributes is tedious process,
37 * you can create a bean which contains getters and setters of all properties
38 * and store the bean as a session attribute:</p>
39 *
40 * <pre>
41 * public class MyContext {
42 * public String getPropertyX() { ... };
43 * public void setPropertyX(String propertyX) { ... };
44 * public int getPropertyZ() { ... };
45 * public void setPropertyZ(int propertyZ) { ... };
46 * }
47 *
48 * public class MyHandlderCommand implements IoHandlerCommand {
49 * public void execute( NextCommand next, IoSession session, Object message ) throws Exception {
50 * MyContext ctx = session.getAttribute( "mycontext" );
51 * ...
52 * }
53 * }
54 * </pre>
55 *
56 * @author The Apache MINA Project (dev@mina.apache.org)
57 */
58 public interface IoHandlerCommand {
59 /**
60 * <p>Execute a unit of processing work to be performed. This
61 * {@link IoHandlerCommand} may either complete the required processing
62 * and just return to stop the processing, or delegate remaining
63 * processing to the next {@link IoHandlerCommand} in a {@link IoHandlerChain}
64 * containing this {@link IoHandlerCommand} by calling
65 * {@link NextCommand#execute(IoSession,Object)}.
66 *
67 * @param next an indirect reference to the next {@link IoHandlerCommand} that
68 * provides a way to forward the request to the next {@link IoHandlerCommand}.
69 * @param session the {@link IoSession} which is associated with
70 * this request
71 * @param message the message object of this request
72 *
73 * @exception Exception general purpose exception return
74 * to indicate abnormal termination
75 */
76 void execute(NextCommand next, IoSession session, Object message)
77 throws Exception;
78
79 /**
80 * Represents an indirect reference to the next {@link IoHandlerCommand} of
81 * the {@link IoHandlerChain}. This interface provides a way to forward
82 * the request to the next {@link IoHandlerCommand}.
83 *
84 * @author The Apache MINA Project (dev@mina.apache.org)
85 */
86 public interface NextCommand {
87 /**
88 * Forwards the request to the next {@link IoHandlerCommand} in the
89 * {@link IoHandlerChain}.
90 */
91 void execute(IoSession session, Object message) throws Exception;
92 }
93 }