Netty之入门案例

用户4919348

发布于 2019-04-18 17:00:37

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发布于 2019-04-18 17:00:37

文章被收录于专栏：波波烤鸭波波烤鸭

前面给大家介绍了NIO，我们会发现用NIO实现异步非阻塞的网络通信代码量非常大，而且并不是很好理解，在实际的开发中一般我们也都是会实现基于NIO的框架来操作的，比如Netty，这样开发效率有高而且Bug也少。

Netty入门案例

官网:https://netty.io/

环境准备

你可以去官网下载对应的jar包依赖，然后创建普通的java项目即可，也可以跟着我通过创建maven项目来实现，如下是会用到的依赖

<dependencies>
	<dependency>
		<groupId>io.netty</groupId>
		<artifactId>netty-all</artifactId>
		<version>5.0.0.Alpha2</version>
	</dependency>

	<dependency>
		<groupId>org.slf4j</groupId>
		<artifactId>slf4j-log4j12</artifactId>
		<version>1.7.25</version>
	</dependency>
</dependencies>

log4j.properties属性文件

log4j.rootCategory=info, stdout , R
 
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=[QC] %p [%t] %C.%M(%L) | %m%n
 
log4j.appender.R=org.apache.log4j.DailyRollingFileAppender
log4j.appender.R.File=C:\\Tomcat 5.5\\logs\\qc.log
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d-[TS] %p %t %c - %m%n

服务端

TimerServer

package com.dpb.netty.demo;

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

public class TimerServer {

	public void bind(int port) throws Exception{
		// 配置服务端的NIO线程组
		// 服务端接受客户端的连接
		NioEventLoopGroup bossGroup = new NioEventLoopGroup();
		// 进行SocketChannel的网络读写
		NioEventLoopGroup workerGroup = new NioEventLoopGroup();
		
		try {
			// 用于启动NIO服务端的辅助启动类，目的是降低服务端的开发复杂度
			ServerBootstrap b = new ServerBootstrap();
			b.group(bossGroup,workerGroup)
			// 设置Channel
			.channel(NioServerSocketChannel.class)
			// 设置TCP参数
			.option(ChannelOption.SO_BACKLOG, 1024)
			// 绑定I/O事件的处理类ChildChannelHandler
			.childHandler(new ChildChannelHandler());
		
		// 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 {
			// 优雅退出，释放线程池资源
			bossGroup.shutdownGracefully();
			workerGroup.shutdownGracefully();
		}
		
	}
	
	private class ChildChannelHandler extends ChannelInitializer<SocketChannel>{

		@Override
		protected void initChannel(SocketChannel arg0) throws Exception {
			arg0.pipeline().addLast(new TimerServerHandler());
			
		}
		
	}
	
	public static void main(String[] args) throws Exception {
		int port = 8080;
		new TimerServer().bind(port);
	}
}

TimerServerHandler

package com.dpb.netty.demo;

import java.nio.ByteBuffer;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerAdapter;
import io.netty.channel.ChannelHandlerContext;
/**
 * 用于对网络事件进行读写操作
 * @author 波波烤鸭
 * @email dengpbs@163.com
 *
 */
public class TimerServerHandler extends ChannelHandlerAdapter{

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		// ByteBuf 类似于NIO中的java.nio.ByteBuffer对象，
		ByteBuf buf = (ByteBuf) msg;
		byte[] req = new byte[buf.readableBytes()];
		buf.readBytes(req);
		String body = new String(req,"utf-8");
		System.out.println("The time server receive order : "+body);
		String currentTime = "Query time order".equalsIgnoreCase(body)?new java.util.Date(System.currentTimeMillis()).toString():"BAD ORDER";
		ByteBuf resp = Unpooled.copiedBuffer(currentTime.getBytes());
		ctx.write(resp);
	}

	@Override
	public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
		// TODO Auto-generated method stub
		ctx.flush();
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		// TODO Auto-generated method stub
		ctx.close();
	}
}

客户端

TimeClient

package com.dpb.netty.demo;

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;

public class TimeClient {
	
	public static void main(String[] args) throws Exception {
		int port = 8080;
		new TimeClient().connect(port, "127.0.0.1");
	}

	public void connect(int port,String host)throws Exception{
		// 配置客户端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<SocketChannel>() {

					@Override
					protected void initChannel(SocketChannel arg0) throws Exception {
						arg0.pipeline().addLast(new TimeClientHandler());
					}
					
				});
			// 发起异步连接操作
			ChannelFuture f = b.connect(host,port).sync();
			// 等待客户端链路关闭
			f.channel().closeFuture().sync();
		}catch(Exception e){
			e.printStackTrace();
		}finally{
			// 优雅退出，释放NIO线程组
			group.shutdownGracefully();
		}
	}
}

TimeClientHandler

package com.dpb.netty.demo;

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;

public class TimeClientHandler extends ChannelHandlerAdapter{

	private static final Logger logger = Logger.getLogger(TimeClientHandler.class.getName());
	
	private final ByteBuf firstMessage;
	
	public TimeClientHandler(){
		byte[] req = "Query time order".getBytes();
		firstMessage = Unpooled.buffer(req.length);
		firstMessage.writeBytes(req);
	}
	
	@Override
	public void channelActive(ChannelHandlerContext ctx) throws Exception {
		ctx.writeAndFlush(firstMessage);
	}

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		ByteBuf buf = (ByteBuf) msg;
		byte[] req  = new  byte[buf.readableBytes()];
		buf.readBytes(req);
		String body = new String(req,"UTF-8");
		System.out.println("Now is :"+body);
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
		// TODO Auto-generated method stub
		logger.warning("Unexpected exception from downstream:"+cause.getMessage());
		ctx.close();
	}
}

测试

先启动服务器，再启动客户端，输出如下: 服务端

The time server receive order : Query time order

客户端

Now is :Thu Apr 11 22:22:58 CST 2019

总结

通过案例使用Netty实现了客户端和服务器的通信，可以发现相比传统的NIO程序，Netty的代码更加简洁，开发难度更低，扩展性也更好，非常适合作为基础通信框架被用户集成和使用

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原始发表：2019年04月11日，如有侵权请联系 cloudcommunity@tencent.com 删除

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