（NIO-框架）--Netty（三）模拟Echo服务器案例--DelimiterBasedFrameDecoder（以分隔符做消息解码）FixedLengthFrameDecoder(定长)

package com.taikang.echo.echoclient;

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

public class EchoClient {

	public void connect(int port, String host) throws Exception {
		EventLoopGroup group = new NioEventLoopGroup();
		try {
			Bootstrap b = new Bootstrap();
			b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true)
					.handler(new ChannelInitializer<SocketChannel>() {
						@Override
						protected void initChannel(SocketChannel ch) throws Exception {
							ByteBuf delimiter = Unpooled.copiedBuffer("$_".getBytes());
							ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiter));
							ch.pipeline().addLast(new StringDecoder());
							ch.pipeline().addLast(new EchoClientHandler());
						}
					});
			// 发起异步连接操作
			ChannelFuture f = b.connect(host, port).sync();
			// 等待客戶端鏈路關閉
			f.channel().closeFuture().sync();
		} finally {
			// 优雅退出，释放NIO线程组
			group.shutdownGracefully();
		}
	}

	public static void main(String[] args) throws Exception {
		int port = 8080;
		if (args != null && args.length > 0) {
			try {
				port = Integer.valueOf(args[0]);
			} catch (NumberFormatException e) {
			}
		}
		new EchoClient().connect(port, "127.0.0.1");
	}
}

package com.taikang.echo.echoclient;

import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class EchoClientHandler extends SimpleChannelInboundHandler<String> {

	private int counter;

	static final String ECHO_REQ = "Hi,LiuYan.Welcome to Netty.$_";

	public EchoClientHandler() {
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		System.out.println("This is " + ++counter + "times receive server : [" + msg + "]");
	}

	@Override
	public void channelActive(ChannelHandlerContext ctx) {
		for (int i = 0; i < 10; i++) {
			//Unpooled.copiedBuffer(ECHO_REQ.getBytes())
			//看了下源码，确认了，上边那个Unpooled...这一堆是把byte数组变成ByteBuf对象，服务端在接受后才能识别啊
			ctx.writeAndFlush(Unpooled.copiedBuffer(ECHO_REQ.getBytes()));
		}
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		ctx.flush();
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
		cause.printStackTrace();
		ctx.close();
	}

	@Override
	protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
	}

}

package com.taikang.echo.echoserver;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
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.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class EchoServer {
	public void bind(int port) throws Exception{
		//配置服务端的NIO线程组
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try{
			ServerBootstrap b = new ServerBootstrap();
			b.group(bossGroup,workerGroup)
				.channel(NioServerSocketChannel.class)
				.option(ChannelOption.SO_BACKLOG, 100)
				.handler(new LoggingHandler(LogLevel.INFO))
				.childHandler(new ChannelInitializer<SocketChannel>() {
					@Override
					public void initChannel(SocketChannel ch) throws Exception {
						//$_作為分隔符
						ByteBuf delimiter = Unpooled.copiedBuffer("$_".getBytes());
						//1024代表单条消息最大长度，当达到最大长度还没有找到分隔符，就抛异常了，后面的参数是分隔符缓冲对象
						ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiter));
						ch.pipeline().addLast(new StringDecoder());
						ch.pipeline().addLast(new EchoServerHandler());
					}
				});
			
			//绑定端口，同步等待成功
			ChannelFuture f = b.bind(port).sync();
			
			//等待服务端监听端口关闭
			f.channel().closeFuture().sync();
		}finally{
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
		}
	}
	
	public static void main(String[] args) throws Exception {
		int port = 8080;
		if(args != null && args.length>0){
			try{
				port = Integer.valueOf(args[0]);
			}catch(NumberFormatException e){
			}
		}
		new EchoServer().bind(port);
	}
}

package com.taikang.echo.echoserver;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;

public class EchoServerHandler extends SimpleChannelInboundHandler<String> {
	
	int counter = 0;

	@Override 
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception{
		System.out.println("服务端channelRead读取到消息");
		String body = (String) msg;
		System.out.println("This is " + ++counter + "times receive client : [" + body + "]");
		body += "$_";
		ByteBuf echo = Unpooled.copiedBuffer(body.getBytes());
		ctx.writeAndFlush(echo);
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
		cause.printStackTrace();
		ctx.close();
	}

	@Override
	protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
		System.out.println("服务端channelRead0读取到消息");
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		ctx.flush();
	}
}

结果如下图：

至于定长那个就是把ch.pipeline().addLast(new DelimiterBasedFrameDecoder(1024, delimiter));

换成ch.pipeline().addLast(new FixedLengthFrameDecoder(20));