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 * 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 io.netty.handler.codec.string;
17
18 import io.netty.buffer.ByteBuf;
19 import io.netty.buffer.ByteBufUtil;
20 import io.netty.channel.ChannelHandler.Sharable;
21 import io.netty.channel.ChannelHandlerContext;
22 import io.netty.channel.ChannelPipeline;
23 import io.netty.handler.codec.LineBasedFrameDecoder;
24 import io.netty.handler.codec.MessageToMessageEncoder;
25
26 import java.nio.CharBuffer;
27 import java.nio.charset.Charset;
28 import java.util.List;
29
30 /**
31 * Encodes the requested {@link String} into a {@link ByteBuf}.
32 * A typical setup for a text-based line protocol in a TCP/IP socket would be:
33 * <pre>
34 * {@link ChannelPipeline} pipeline = ...;
35 *
36 * // Decoders
37 * pipeline.addLast("frameDecoder", new {@link LineBasedFrameDecoder}(80));
38 * pipeline.addLast("stringDecoder", new {@link StringDecoder}(CharsetUtil.UTF_8));
39 *
40 * // Encoder
41 * pipeline.addLast("stringEncoder", new {@link StringEncoder}(CharsetUtil.UTF_8));
42 * </pre>
43 * and then you can use a {@link String} instead of a {@link ByteBuf}
44 * as a message:
45 * <pre>
46 * void channelRead({@link ChannelHandlerContext} ctx, {@link String} msg) {
47 * ch.write("Did you say '" + msg + "'?\n");
48 * }
49 * </pre>
50 */
51 @Sharable
52 public class StringEncoder extends MessageToMessageEncoder<CharSequence> {
53
54 // TODO Use CharsetEncoder instead.
55 private final Charset charset;
56
57 /**
58 * Creates a new instance with the current system character set.
59 */
60 public StringEncoder() {
61 this(Charset.defaultCharset());
62 }
63
64 /**
65 * Creates a new instance with the specified character set.
66 */
67 public StringEncoder(Charset charset) {
68 if (charset == null) {
69 throw new NullPointerException("charset");
70 }
71 this.charset = charset;
72 }
73
74 @Override
75 protected void encode(ChannelHandlerContext ctx, CharSequence msg, List<Object> out) throws Exception {
76 if (msg.length() == 0) {
77 return;
78 }
79
80 out.add(ByteBufUtil.encodeString(ctx.alloc(), CharBuffer.wrap(msg), charset));
81 }
82 }