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.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 import io.netty.util.internal.ObjectUtil;
26
27 import java.nio.CharBuffer;
28 import java.nio.charset.Charset;
29 import java.util.List;
30
31 /**
32 * Encodes the requested {@link String} into a {@link ByteBuf}.
33 * A typical setup for a text-based line protocol in a TCP/IP socket would be:
34 * <pre>
35 * {@link ChannelPipeline} pipeline = ...;
36 *
37 * // Decoders
38 * pipeline.addLast("frameDecoder", new {@link LineBasedFrameDecoder}(80));
39 * pipeline.addLast("stringDecoder", new {@link StringDecoder}(CharsetUtil.UTF_8));
40 *
41 * // Encoder
42 * pipeline.addLast("stringEncoder", new {@link StringEncoder}(CharsetUtil.UTF_8));
43 * </pre>
44 * and then you can use a {@link String} instead of a {@link ByteBuf}
45 * as a message:
46 * <pre>
47 * void channelRead({@link ChannelHandlerContext} ctx, {@link String} msg) {
48 * ch.write("Did you say '" + msg + "'?\n");
49 * }
50 * </pre>
51 */
52 @Sharable
53 public class StringEncoder extends MessageToMessageEncoder<CharSequence> {
54
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 this.charset = ObjectUtil.checkNotNull(charset, "charset");
69 }
70
71 @Override
72 protected void encode(ChannelHandlerContext ctx, CharSequence msg, List<Object> out) throws Exception {
73 if (msg.length() == 0) {
74 return;
75 }
76
77 out.add(ByteBufUtil.encodeString(ctx.alloc(), CharBuffer.wrap(msg), charset));
78 }
79 }