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.string;
17
18 import java.nio.charset.Charset;
19
20 import org.jboss.netty.buffer.ChannelBuffer;
21 import org.jboss.netty.channel.Channel;
22 import org.jboss.netty.channel.ChannelHandlerContext;
23 import org.jboss.netty.channel.ChannelPipeline;
24 import org.jboss.netty.channel.MessageEvent;
25 import org.jboss.netty.channel.ChannelHandler.Sharable;
26 import org.jboss.netty.handler.codec.frame.DelimiterBasedFrameDecoder;
27 import org.jboss.netty.handler.codec.frame.Delimiters;
28 import org.jboss.netty.handler.codec.frame.FrameDecoder;
29 import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
30
31 /**
32 * Decodes a received {@link ChannelBuffer} into a {@link String}. Please
33 * note that this decoder must be used with a proper {@link FrameDecoder}
34 * such as {@link DelimiterBasedFrameDecoder} if you are using a stream-based
35 * transport such as TCP/IP. A typical setup for a text-based line protocol
36 * in a TCP/IP socket would be:
37 * <pre>
38 * {@link ChannelPipeline} pipeline = ...;
39 *
40 * // Decoders
41 * pipeline.addLast("frameDecoder", new {@link DelimiterBasedFrameDecoder}(80, {@link Delimiters#lineDelimiter()}));
42 * pipeline.addLast("stringDecoder", new {@link StringDecoder}(CharsetUtil.UTF_8));
43 *
44 * // Encoder
45 * pipeline.addLast("stringEncoder", new {@link StringEncoder}(CharsetUtil.UTF_8));
46 * </pre>
47 * and then you can use a {@link String} instead of a {@link ChannelBuffer}
48 * as a message:
49 * <pre>
50 * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
51 * String msg = (String) e.getMessage();
52 * ch.write("Did you say '" + msg + "'?\n");
53 * }
54 * </pre>
55 *
56 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
57 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
58 *
59 * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
60 *
61 * @apiviz.landmark
62 */
63 @Sharable
64 public class StringDecoder extends OneToOneDecoder {
65
66 // TODO Use CharsetDecoder instead.
67 private final Charset charset;
68
69 /**
70 * Creates a new instance with the current system character set.
71 */
72 public StringDecoder() {
73 this(Charset.defaultCharset());
74 }
75
76 /**
77 * Creates a new instance with the specified character set.
78 */
79 public StringDecoder(Charset charset) {
80 if (charset == null) {
81 throw new NullPointerException("charset");
82 }
83 this.charset = charset;
84 }
85
86 /**
87 * @deprecated Use {@link #StringDecoder(Charset)} instead.
88 */
89 @Deprecated
90 public StringDecoder(String charsetName) {
91 this(Charset.forName(charsetName));
92 }
93
94 @Override
95 protected Object decode(
96 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
97 if (!(msg instanceof ChannelBuffer)) {
98 return msg;
99 }
100 return ((ChannelBuffer) msg).toString(charset);
101 }
102 }