1 /*
2 * Copyright 2012 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://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 io.netty.handler.codec.string;
17
18 import io.netty.buffer.ByteBuf;
19 import io.netty.channel.ChannelHandler.Sharable;
20 import io.netty.channel.ChannelHandlerContext;
21 import io.netty.channel.ChannelPipeline;
22 import io.netty.handler.codec.ByteToMessageDecoder;
23 import io.netty.handler.codec.DelimiterBasedFrameDecoder;
24 import io.netty.handler.codec.LineBasedFrameDecoder;
25 import io.netty.handler.codec.MessageToMessageDecoder;
26 import io.netty.util.internal.ObjectUtil;
27
28 import java.nio.charset.Charset;
29 import java.util.List;
30
31 /**
32 * Decodes a received {@link ByteBuf} into a {@link String}. Please
33 * note that this decoder must be used with a proper {@link ByteToMessageDecoder}
34 * such as {@link DelimiterBasedFrameDecoder} or {@link LineBasedFrameDecoder}
35 * if you are using a stream-based transport such as TCP/IP. A typical setup for a
36 * text-based line protocol in a TCP/IP socket would be:
37 * <pre>
38 * {@link ChannelPipeline} pipeline = ...;
39 *
40 * // Decoders
41 * pipeline.addLast("frameDecoder", new {@link LineBasedFrameDecoder}(80));
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 ByteBuf}
48 * as a message:
49 * <pre>
50 * void channelRead({@link ChannelHandlerContext} ctx, {@link String} msg) {
51 * ch.write("Did you say '" + msg + "'?\n");
52 * }
53 * </pre>
54 */
55 @Sharable
56 public class StringDecoder extends MessageToMessageDecoder<ByteBuf> {
57
58 // TODO Use CharsetDecoder instead.
59 private final Charset charset;
60
61 /**
62 * Creates a new instance with the current system character set.
63 */
64 public StringDecoder() {
65 this(Charset.defaultCharset());
66 }
67
68 /**
69 * Creates a new instance with the specified character set.
70 */
71 public StringDecoder(Charset charset) {
72 this.charset = ObjectUtil.checkNotNull(charset, "charset");
73 }
74
75 @Override
76 protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception {
77 out.add(msg.toString(charset));
78 }
79 }