1 /*
2 * Copyright 2009 Red Hat, Inc.
3 *
4 * Red Hat licenses this file to you under the Apache License, version 2.0
5 * (the "License"); you may not use this file except in compliance with the
6 * License. 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, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package org.jboss.netty.handler.codec.oneone;
17
18 import static org.jboss.netty.channel.Channels.*;
19
20 import org.jboss.netty.buffer.ChannelBuffers;
21 import org.jboss.netty.channel.Channel;
22 import org.jboss.netty.channel.ChannelDownstreamHandler;
23 import org.jboss.netty.channel.ChannelEvent;
24 import org.jboss.netty.channel.ChannelHandlerContext;
25 import org.jboss.netty.channel.ChannelPipeline;
26 import org.jboss.netty.channel.MessageEvent;
27 import org.jboss.netty.handler.codec.frame.DelimiterBasedFrameDecoder;
28 import org.jboss.netty.handler.codec.frame.Delimiters;
29
30 /**
31 * Transforms a write request into another write request. A typical setup for
32 * TCP/IP would be:
33 * <pre>
34 * {@link ChannelPipeline} pipeline = ...;
35 *
36 * // Decoders
37 * pipeline.addLast("frameDecoder", new {@link DelimiterBasedFrameDecoder}(80, {@link Delimiters#nulDelimiter()}));
38 * pipeline.addLast("customDecoder", new {@link OneToOneDecoder}() { ... });
39 *
40 * // Encoder
41 * pipeline.addLast("customEncoder", new {@link OneToOneEncoder}() { ... });
42 * </pre>
43 *
44 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
45 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
46 *
47 * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
48 *
49 * @apiviz.landmark
50 */
51 public abstract class OneToOneEncoder implements ChannelDownstreamHandler {
52
53 protected OneToOneEncoder() {
54 super();
55 }
56
57 public void handleDownstream(
58 ChannelHandlerContext ctx, ChannelEvent evt) throws Exception {
59 if (!(evt instanceof MessageEvent)) {
60 ctx.sendDownstream(evt);
61 return;
62 }
63
64 MessageEvent e = (MessageEvent) evt;
65 Object originalMessage = e.getMessage();
66 Object encodedMessage = encode(ctx, e.getChannel(), originalMessage);
67 if (originalMessage == encodedMessage) {
68 ctx.sendDownstream(evt);
69 } else if (encodedMessage != null) {
70 write(ctx, e.getFuture(), encodedMessage, e.getRemoteAddress());
71 }
72 }
73
74 /**
75 * Transforms the specified message into another message and return the
76 * transformed message. Note that you can not return {@code null}, unlike
77 * you can in {@link OneToOneDecoder#decode(ChannelHandlerContext, Channel, Object)};
78 * you must return something, at least {@link ChannelBuffers#EMPTY_BUFFER}.
79 */
80 protected abstract Object encode(
81 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception;
82 }