Netty学习一 HelloWorld

1、netty服务端开发套路

> 1、创建线程组，指定负责连接客户端的通道 > 2、初始化通道，该类继承ChannelInitializer类，并指定各种Handler > 3、添加自定义Handler，需要继承ChannelInboundHandlerAdapter

2、maven依赖

``` io.netty netty-all 4.1.6.Final ```

3、服务端

入口

public class HelloWorldServer {
	
	private int port;
	
	public HelloWorldServer(int port) {
		this.port = port;
	}
	
	public void start(){
		EventLoopGroup bossGroup = new NioEventLoopGroup();//创建父子线程组
		EventLoopGroup workGroup = new NioEventLoopGroup();
		
		ServerBootstrap server = new ServerBootstrap();
		server.group(bossGroup, workGroup)
			  .channel(NioServerSocketChannel.class)//指定处理客户端的通道
			  .childHandler(new ServerChannelInitializer());//通道初始化
		
		try {
			ChannelFuture future = server.bind(port).sync();
			future.channel().closeFuture().sync();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} finally{
			bossGroup.shutdownGracefully();
			workGroup.shutdownGracefully();
		}
	}

	public static void main(String[] args) {
		HelloWorldServer server = new HelloWorldServer(8888);
		server.start();
	}

}

通道初始化

public class ServerChannelInitializer extends ChannelInitializer<SocketChannel> {

	@Override
	protected void initChannel(SocketChannel socketChannel) throws Exception {
		ChannelPipeline pipeline = socketChannel.pipeline();
		pipeline.addLast("decoder", new StringDecoder());// 字符串解码和编码
		pipeline.addLast("encoder", new StringEncoder());
		pipeline.addLast("handler", new HelloWordServerHandler());//自定义handler
	}

}

自定义处理器

public class HelloWordServerHandler extends ChannelInboundHandlerAdapter {

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
		System.out.println("服务端收到消息:[" + msg + "]");
		ctx.writeAndFlush("欢迎你,客户端");
	}

}

4、客户端

### 入口 ``` public class HelloWorldClient {

private int port;
private String address;

public HelloWorldClient(int port, String address) {
	this.port = port;
	this.address = address;
}

public void start() {
	EventLoopGroup group = new NioEventLoopGroup();

	Bootstrap bootstrap = new Bootstrap();
	bootstrap.group(group).channel(NioSocketChannel.class)
			.handler(new ClientChannelInitializer());

	try {
		ChannelFuture future = bootstrap.connect(address,port).sync();
		Channel channel = future.channel();
		channel.writeAndFlush("我是客户端,地址:" + channel.remoteAddress());
		channel.closeFuture().sync();
	} catch (Exception e) {
		e.printStackTrace();
	} finally {
		group.shutdownGracefully();
	}
}

public static void main(String[] args) {
	HelloWorldClient client = new HelloWorldClient(8888, "127.0.0.1");
	client.start();
}

}

### 通道初始化

public class ClientChannelInitializer extends ChannelInitializer {

@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
	ChannelPipeline pipeline = socketChannel.pipeline();

	pipeline.addLast("decoder", new StringDecoder());//字符串解码和编码
	pipeline.addLast("encoder", new StringEncoder());
	pipeline.addLast("handler", new HelloWorldClientHandler());//自定义handler
}

}

### 自定义处理器

public class HelloWorldClientHandler extends ChannelInboundHandlerAdapter {

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
	System.out.println("客户端收到消息:[" + msg + "]");
}

}

<h1>5、运行</h1>
先启动服务端，再启动客户端，可以看到，服务端和客户端分别收到了对方发送的消息
### 服务端收到消息
![](https://img2018.cnblogs.com/blog/1373276/201906/1373276-20190603163957020-260958172.png)
### 客户端收到消息
![](https://img2018.cnblogs.com/blog/1373276/201906/1373276-20190603164006441-471814764.png)