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Netty内部实现了很多通用协议的编码和解码。如果要实现自定义的协议，则需要自己实现编码或解码的功能。 继承ChannelInboundHandlerAdapter类，就可以实现一个自定义的解码器。但如果发送比较长的内容，则会出现内容读取不完整的问题。其实比较简单的一个实现，就是设定协议头的几个字节为消息的长度即可，并在发送消息和处理消息时，处理消息的长度即可。Server端的代码如下：TcpServer.javaimport org.apache.log4j.Logger; import org.apache.log4j.PropertyConfigurator; import io.netty.bootstrap.ServerBootstrap; import io.netty.channel.ChannelInitializer; import io.netty.channel.ChannelOption;import io.netty.channel.ChannelPipeline; import io.netty.channel.EventLoopGroup; import io.netty.channel.nio.NioEventLoopGroup; import io.netty.channel.socket.SocketChannel; import io.netty.channel.socket.nio.NioServerSocketChannel; import io.netty.handler.codec.LengthFieldBasedFrameDecoder; import io.netty.handler.codec.LengthFieldPrepender; import io.netty.handler.codec.bytes.ByteArrayDecoder;import io.netty.handler.codec.bytes.ByteArrayEncoder;import io.netty.handler.codec.protobuf.ProtobufDecoder;import io.netty.handler.codec.serialization.ClassResolvers;import io.netty.handler.codec.serialization.ObjectDecoder;import io.netty.handler.codec.serialization.ObjectEncoder;import io.netty.handler.codec.string.StringDecoder; import io.netty.handler.codec.string.StringEncoder; import io.netty.util.CharsetUtil; public class TcpServer { private static final Logger logger = Logger.getLogger(TcpServer.class); private static final String IP = "127.0.0.1"; private static final int PORT = 9999; protected static final int BIZGROUPSIZE = Runtime.getRuntime().availableProcessors()*2; //默认 protected static final int BIZTHREADSIZE = 4; private static final EventLoopGroup bossGroup = new NioEventLoopGroup(BIZGROUPSIZE); private static final EventLoopGroup workerGroup = new NioEventLoopGroup(BIZTHREADSIZE); protected static void run() throws Exception { ServerBootstrap b = new ServerBootstrap(); b.group(bossGroup, workerGroup); b.channel(NioServerSocketChannel.class); b.childHandler(new ChannelInitializer() { @Override public void initChannel(SocketChannel ch) throws Exception { ChannelPipeline pipeline = ch.pipeline(); pipeline.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(Integer.MAX_VALUE, 0, 4, 0, 4)); pipeline.addLast("frameEncoder", new LengthFieldPrepender(4)); // pipeline.addLast("decoder", new StringDecoder(CharsetUtil.UTF_8)); // pipeline.addLast("encoder", new StringEncoder(CharsetUtil.UTF_8)); pipeline.addLast(new SocketByteHandler()); } }); b.bind(IP, PORT).sync(); logger.info("TCP服务器已启动"); } protected static void shutdown() { workerGroup.shutdownGracefully(); bossGroup.shutdownGracefully(); } public static void main(String[] args) throws Exception { PropertyConfigurator.configure("log/log4j.properties"); logger.info("开始启动TCP服务器..."); TcpServer.run(); // TcpServer.shutdown(); } } LengthFieldBasedFrameDecoder和LengthFieldPrepender就是设定协议头长度的，我这里设定协议头的长度为4个字节。协议处理类：SocketByteHandler.javaimport java.nio.ByteBuffer;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;public class SocketByteHandler extends ChannelInboundHandlerAdapter {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg)throws Exception {// super.channelRead(ctx, msg);ByteBuf result = (ByteBuf) msg;byte[] result1 = new byte[result.readableBytes()]; // msg中存储的是ByteBuf类型的数据，把数据读取到byte[]中 result.readBytes(result1); String resultStr = new String(result1); System.out.println("Client said:" + resultStr); // 释放资源，这行很关键 result.release(); String response = "I am ok!"; // 在当前场景下，发送的数据必须转换成ByteBuf数组 ByteBuf encoded = ctx.alloc().buffer(4 * response.length()); encoded.writeBytes(response.getBytes()); ctx.write(encoded); ctx.flush(); }@Overridepublic void channelReadComplete(ChannelHandlerContext ctx) throws Exception {// TODO Auto-generated method stubsuper.channelReadComplete(ctx);ctx.flush();}}客户端可以使用最简单的socket来实现即可，如：public static void sendMsgBySocket(byte[] msg){ try {Socket socket = new Socket();socket.connect(new InetSocketAddress(HOST,PORT));socket.setKeepAlive(true);OutputStream out = socket.getOutputStream();ByteBuffer header = ByteBuffer.allocate(4);header.putInt(msg.length);out.write(header.array());out.write(msg);out.flush();InputStream in = socket.getInputStream();byte[] buff = new byte[4096];int readed = in.read(buff);if(readed > 0){String str = new String(buff,4,readed);logger.info("client received msg from server:"+str);}out.close();} catch (UnknownHostException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} }可以看到，header中就是给出的要发送的消息内容的总长度，但不包含协议头。这样，server端收到后，会自动忽略掉协议头的内容，这就是Netty的好处。客户端如果读取server端的返回内容，而且用基本的socket（非Netty），则需要自己处理协议头：String str = new String(buff,4,readed);跳过协议头的4个字节长度后，就是Server端返回的真正的内容。给我老师的人工智能教程打call！http://blog.csdn.net/jiangjunshow
