Netty5中使用LineBasedFrameDecoder解决TCP粘包问题

为了解决TCP粘包/拆包导致的半包读写问题，Netty默认提供了多种编解码器用于处理该类问题，本例程将展示Netty中LineBasedFrameDecoder的使用

/**
 * 
 */
package upup.me.netty.practice02;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;

/**
 * @author Administrator
 *
 */
public class TimeServer {

	public void bind(int port) {
		// 配置服务端的NIO线程组
		EventLoopGroup bossGroup = new NioEventLoopGroup();
		EventLoopGroup workerGroup = new NioEventLoopGroup();
		try {
			ServerBootstrap b = new ServerBootstrap();

			// 设置线程组及Socket参数
			b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 1024)
					.childHandler(new ChildChannelHandler());

			// 绑定端口，同步等待成功
			ChannelFuture f = b.bind(port).sync();
			System.out.println("服务已经启动,端口:" + port);

			f.channel().closeFuture().sync();
		} catch (Exception e) {
		} finally {
			// 退出释放线程池资源
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
			System.out.println("服务销毁!");
		}
	}

	public static void main(String[] args) {
		int port = 8080;
		if (null != args && args.length > 0) {
			try {
				port = Integer.valueOf(args[0]);
			} catch (Exception e) {
				// 采用默认值
			}
		}
		new TimeServer().bind(port);
	}

}

/**
 * 
 */
package upup.me.netty.practice02;

import java.util.Date;

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

/**
 * @author Administrator
 *
 */
public class TimeServerHandler extends ChannelHandlerAdapter {

	private int counter;

	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		String body = (String) msg;
		System.out.println("The time server receive order:" + body + ";the counter is:" + (++counter));
		String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new Date(System.currentTimeMillis()).toString()
				: "BAD ORDER";
		currentTime = currentTime + System.getProperty("line.separator");
		ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
		ctx.write(resp);
	}

	public void channelReadComplete(ChannelHandlerContext ctx) {
		ctx.flush();
	}

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

}

/**
 * 
 */
package upup.me.netty.practice02;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @author Administrator
 *
 */
public class ChildChannelHandler extends ChannelInitializer {

	@Override
	protected void initChannel(SocketChannel ch) throws Exception {
		// 以下两行代码为了解决半包读问题
		ch.pipeline().addLast(new LineBasedFrameDecoder(1024));
		ch.pipeline().addLast(new StringDecoder());

		ch.pipeline().addLast(new TimeServerHandler());
	}

}

/**
 * 
 */
package upup.me.netty.practice02;

import io.netty.bootstrap.Bootstrap;
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.LineBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;

/**
 * @author Administrator
 *
 */
public class TimeClient {

	public void connect(int port, String host) {
		// 配置客户端的NIO线程组
		EventLoopGroup group = new NioEventLoopGroup();
		try {
			Bootstrap b = new Bootstrap();
			b.group(group).channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true)
					.handler(new ChannelInitializer() {
						@Override
						public void initChannel(SocketChannel ch) throws Exception {
							// 以下两行代码为了解决半包读问题
							ch.pipeline().addLast(new LineBasedFrameDecoder(1024));
							ch.pipeline().addLast(new StringDecoder());

							ch.pipeline().addLast(new TimeClientHandler());
						}
					});
			// 发起异步连接操作
			ChannelFuture f = b.connect(host, port).sync();

			// 等待链路关闭
			f.channel().closeFuture().sync();

		} catch (Exception e) {
		} finally {
			// 退出，释放NIO线程组
			group.shutdownGracefully();
		}
	}

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

/**
 * 
 */
package upup.me.netty.practice02;

import java.io.UnsupportedEncodingException;
import java.util.logging.Logger;

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

/**
 * @author Administrator
 *
 */
public class TimeClientHandler extends ChannelHandlerAdapter {

	private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());

	private int counter;

	private byte[] req;

	public TimeClientHandler() {
		req = ("QUERY TIME ORDER" + System.getProperty("line.separator")).getBytes();
	}

	public void channelActive(ChannelHandlerContext ctx) {
		ByteBuf message = null;
		for (int i = 0; i < 100; i++) {
			message = Unpooled.buffer(req.length);
			message.writeBytes(req);
			ctx.writeAndFlush(message);
		}
	}

	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		String body = (String) msg;
		System.out.println("Now is:" + body + "; the counter is:" + (++counter));
	}

	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
		logger.warning("Unexcepted exception from downstream:" + cause.getMessage());
		ctx.close();
	}

}