01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one
03: * or more contributor license agreements. See the NOTICE file
04: * distributed with this work for additional information
05: * regarding copyright ownership. The ASF licenses this file
06: * to you under the Apache License, Version 2.0 (the
07: * "License"); you may not use this file except in compliance
08: * with the License. You may obtain a copy of the License at
09: *
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.common.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 <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
57: * @version $Rev: 576217 $, $Date: 2007-09-16 17:55:27 -0600 (Sun, 16 Sep 2007) $
58: */
59: public interface IoHandlerCommand {
60: /**
61: * <p>Execute a unit of processing work to be performed. This
62: * {@link IoHandlerCommand} may either complete the required processing
63: * and just return to stop the processing, or delegate remaining
64: * processing to the next {@link IoHandlerCommand} in a {@link IoHandlerChain}
65: * containing this {@link IoHandlerCommand} by calling
66: * {@link NextCommand#execute(IoSession,Object)}.
67: *
68: * @param next an indirect reference to the next {@link IoHandlerCommand} that
69: * provides a way to forward the request to the next {@link IoHandlerCommand}.
70: * @param session the {@link IoSession} which is associated with
71: * this request
72: * @param message the message object of this request
73: *
74: * @exception Exception general purpose exception return
75: * to indicate abnormal termination
76: */
77: void execute(NextCommand next, IoSession session, Object message)
78: throws Exception;
79:
80: /**
81: * Represents an indirect reference to the next {@link IoHandlerCommand} of
82: * the {@link IoHandlerChain}. This interface provides a way to forward
83: * the request to the next {@link IoHandlerCommand}.
84: *
85: * @author The Apache MINA Project (dev@mina.apache.org)
86: * @version $Rev: 576217 $, $Date: 2007-09-16 17:55:27 -0600 (Sun, 16 Sep 2007) $
87: */
88: public interface NextCommand {
89: /**
90: * Forwards the request to the next {@link IoHandlerCommand} in the
91: * {@link IoHandlerChain}.
92: */
93: void execute(IoSession session, Object message)
94: throws Exception;
95: }
96: }
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