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.netty5.handler.codec.string;
17
18 import io.netty5.buffer.api.Buffer;
19 import io.netty5.channel.ChannelHandlerContext;
20 import io.netty5.channel.ChannelPipeline;
21 import io.netty5.handler.codec.DelimiterBasedFrameDecoder;
22 import io.netty5.handler.codec.LineBasedFrameDecoder;
23 import io.netty5.handler.codec.MessageToMessageDecoder;
24
25 import java.nio.charset.Charset;
26
27 import static java.util.Objects.requireNonNull;
28
29 /**
30 * Decodes a received {@link Buffer} into a {@link String}. Please
31 * note that this decoder must be used with a proper {@link ByteToMessageDecoder}
32 * such as {@link DelimiterBasedFrameDecoder} or {@link LineBasedFrameDecoder}
33 * if you are using a stream-based transport such as TCP/IP. A typical setup for a
34 * text-based line protocol in a TCP/IP socket would be:
35 * <pre>
36 * {@link ChannelPipeline} pipeline = ...;
37 *
38 * // Decoders
39 * pipeline.addLast("frameDecoder", new {@link LineBasedFrameDecoder}(80));
40 * pipeline.addLast("stringDecoder", new {@link StringDecoder}(CharsetUtil.UTF_8));
41 *
42 * // Encoder
43 * pipeline.addLast("stringEncoder", new {@link StringEncoder}(CharsetUtil.UTF_8));
44 * </pre>
45 * and then you can use a {@link String} instead of a {@link Buffer}
46 * as a message:
47 * <pre>
48 * void channelRead({@link ChannelHandlerContext} ctx, {@link String} msg) {
49 * ch.write("Did you say '" + msg + "'?\n");
50 * }
51 * </pre>
52 */
53 public class StringDecoder extends MessageToMessageDecoder<Buffer> {
54
55 // TODO Use CharsetDecoder instead.
56 private final Charset charset;
57
58 /**
59 * Creates a new instance with the current system character set.
60 */
61 public StringDecoder() {
62 this(Charset.defaultCharset());
63 }
64
65 /**
66 * Creates a new instance with the specified character set.
67 */
68 public StringDecoder(Charset charset) {
69 requireNonNull(charset, "charset");
70 this.charset = charset;
71 }
72
73 @Override
74 public boolean isSharable() {
75 return true;
76 }
77
78 @Override
79 protected void decode(ChannelHandlerContext ctx, Buffer msg) throws Exception {
80 ctx.fireChannelRead(msg.toString(charset));
81 }
82 }