Netty之入门案例

比眉伴天荒 2022-02-19 22:49 234阅读 0赞

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/][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();
    	}
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcGItYm9ib2thb3lhLXNtLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]

## 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

[https_netty.io]: https://netty.io/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9kcGItYm9ib2thb3lhLXNtLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]: /images/20220220/b257fdeb625f49e2a706aefcb051ad98.png