netty快速入门基本用法

1、netty的基本工作流程

在netty中存在以下的核心组件：

ServerBootstrap：服务器端启动辅助对象；
Bootstrap：客户端启动辅助对象；
Channel：通道，代表一个连接，每个Client请对会对应到具体的一个–Channel；
ChannelPipeline：责任链，每个Channel都有且仅有一个ChannelPipeline与之对应，里面是各种各样的Handler；
handler：用于处理出入站消息及相应的事件，实现我们自己要的业务逻辑；
EventLoopGroup：I/O线程池，负责处理Channel对应的I/O事件；
ChannelInitializer：Channel初始化器；
ChannelFuture：代表I/O操作的执行结果，通过事件机制，获取执行结果，通过添加监听器，执行我们想要的操作；
ByteBuf：字节序列，通过ByteBuf操作基础的字节数组和缓冲区。
我们结合其核心组件通过下图，可以清晰的看明白netty的基本工作原理：

2、代码示例

客户端配置：

package com.xsd.netty;import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;import java.io.Serializable;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;public class AppClient implements Serializable {public void run() {//定义线程池 EventLoopGroupNioEventLoopGroup group = new NioEventLoopGroup();//启动一个客户端需要辅助类bootstrapBootstrap bootstrap = new Bootstrap();try {bootstrap = bootstrap.group(group).remoteAddress(new InetSocketAddress(8080))//初始化一个channel.channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel socketChannel) throws Exception {//为这个Channel通道添加一个Handler处理器socketChannel.pipeline().addLast(new MyChannelHandler2());}});//尝试连接服务器ChannelFuture channelFuture = null;channelFuture = bootstrap.connect().sync();//获取channel，并写出数据channelFuture.channel().writeAndFlush(Unpooled.copiedBuffer("hello netty".getBytes(StandardCharsets.UTF_8)));//阻塞程序，等待接收消息channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {e.printStackTrace();} finally {try {group.shutdownGracefully().sync();} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) {new AppClient().run();}
}

服务端配置:

package com.xsd.netty;import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;public class AppServer {private int port;public AppServer(int port) {this.port = port;}public void start() {// 1.创建eventloop,老板只负责处理请求，之后会将请求分发至workerNioEventLoopGroup boss = new NioEventLoopGroup(2);NioEventLoopGroup worker = new NioEventLoopGroup(10);try {//2.需要一个服务器引导程序ServerBootstrap serverBootstrap = new ServerBootstrap();//3.配置服务器serverBootstrap = serverBootstrap.group(boss, worker).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel socketChannel) throws Exception {//为这个Channel通道添加一个Handler处理器socketChannel.pipeline().addLast(new MyChannelHandler());}});//4.绑定端口ChannelFuture channelFuture = serverBootstrap.bind(port).sync();channelFuture.channel().closeFuture().sync();} catch (InterruptedException e) {e.printStackTrace();}finally {try {boss.shutdownGracefully().sync();worker.shutdownGracefully().sync();} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) {new AppServer(8080).start();}
}

服务端的处理器：

package com.xsd.netty;import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;public class MyChannelHandler extends ChannelInboundHandlerAdapter  {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {ByteBuf byteBuf = (ByteBuf)msg;System.out.println("服务端已经接收到了消息，-->" + byteBuf.toString(StandardCharsets.UTF_8));//可以通过ctx获取channelctx.channel().writeAndFlush(Unpooled.copiedBuffer("hello client".getBytes(StandardCharsets.UTF_8)));}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {//出现异常的时候执行的动作（打印并关闭通道）cause.printStackTrace();ctx.close();}
}

客户端的处理器：

package com.xsd.netty;import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;import java.nio.charset.StandardCharsets;@ChannelHandler.Sharable
public class MyChannelHandler2 extends ChannelInboundHandlerAdapter  {@Overridepublic void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {ByteBuf byteBuf = (ByteBuf)msg;System.out.println("客户端已经接收到了消息，-->" + byteBuf.toString(StandardCharsets.UTF_8));//可以通过ctx获取channel//ctx.channel().writeAndFlush("hello client");}@Overridepublic void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {//出现异常的时候执行的动作（打印并关闭通道）cause.printStackTrace();ctx.close();}
}