1 /*
2 * Copyright 2016 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.CharsetUtil;
26 import io.netty.util.internal.ObjectUtil;
27
28 import java.nio.CharBuffer;
29 import java.nio.charset.Charset;
30 import java.util.List;
31
32 /**
33 * Apply a line separator to the requested {@link String} and encode it into a {@link ByteBuf}.
34 * A typical setup for a 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("lineEncoder", new {@link LineEncoder}(LineSeparator.UNIX, CharsetUtil.UTF_8));
44 * </pre>
45 * and then you can use a {@link String} instead of a {@link ByteBuf}
46 * as a message:
47 * <pre>
48 * void channelRead({@link ChannelHandlerContext} ctx, {@link String} msg) {
49 * ch.write("Did you say '" + msg + "'?");
50 * }
51 * </pre>
52 */
53 @Sharable
54 public class LineEncoder extends MessageToMessageEncoder<CharSequence> {
55
56 private final Charset charset;
57 private final byte[] lineSeparator;
58
59 /**
60 * Creates a new instance with the current system line separator and UTF-8 charset encoding.
61 */
62 public LineEncoder() {
63 this(LineSeparator.DEFAULT, CharsetUtil.UTF_8);
64 }
65
66 /**
67 * Creates a new instance with the specified line separator and UTF-8 charset encoding.
68 */
69 public LineEncoder(LineSeparator lineSeparator) {
70 this(lineSeparator, CharsetUtil.UTF_8);
71 }
72
73 /**
74 * Creates a new instance with the specified character set.
75 */
76 public LineEncoder(Charset charset) {
77 this(LineSeparator.DEFAULT, charset);
78 }
79
80 /**
81 * Creates a new instance with the specified line separator and character set.
82 */
83 public LineEncoder(LineSeparator lineSeparator, Charset charset) {
84 this.charset = ObjectUtil.checkNotNull(charset, "charset");
85 this.lineSeparator = ObjectUtil.checkNotNull(lineSeparator, "lineSeparator").value().getBytes(charset);
86 }
87
88 @Override
89 protected void encode(ChannelHandlerContext ctx, CharSequence msg, List<Object> out) throws Exception {
90 ByteBuf buffer = ByteBufUtil.encodeString(ctx.alloc(), CharBuffer.wrap(msg), charset, lineSeparator.length);
91 buffer.writeBytes(lineSeparator);
92 out.add(buffer);
93 }
94 }