netty入门启动

maven

		<dependency>
			<groupId>io.netty</groupId>
			<artifactId>netty-all</artifactId>
			<version>${netty.version}</version>
		</dependency>

netty启动类

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

public class NioServer {
    
    
	public static void main(String[] args) {
    
    
		new NioServer().start();
	}
	private void start() {
    
    
		EventLoopGroup group = new NioEventLoopGroup();
		try {
    
    
			ServerBootstrap bootstrap = new ServerBootstrap();
			bootstrap.group(group)
			.channel(NioServerSocketChannel.class)
			.localAddress(8888)
			.childHandler(new ChannelInitializer<Channel>() {
    
    
				@Override
				protected void initChannel(Channel ch) throws Exception {
    
    
					ch.pipeline()
					//这里添加处理器
					.addLast(new MyNioServerHandler());
						
				}
			});
			ChannelFuture future = bootstrap.bind().sync();
			
			System.out.println("=======netty启动");
			future.channel().closeFuture().sync();
		} catch (Exception e) {
    
    
			e.printStackTrace();
		} finally {
    
    
			group.shutdownGracefully();
		}

	}
}

所有的启动类基本上都一致,复制即可.
需要注意的是,本类启动了8888端口作为netty的接收端口.
其次,在addLast(new MyNioServerHandler());这里,添加了一个处理器叫做MyNioServerHandler,其实pipeline这里是处理器链,仍然可以添加其他处理器.
MyNioServerHandler是自定义的处理器,我们看一个简单的例子

简单处理器

import java.nio.charset.Charset;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class MyNioServerHandler extends ChannelInboundHandlerAdapter {
    
    

	@Override
	public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
    

		ByteBuf bb = (ByteBuf) msg;
		String msgStr = bb.toString(Charset.forName("UTF-8")); 这个相当于转成字符串
		System.out.println("read " + msgStr);//打印发来的东西
		ctx.writeAndFlush(msg);//把发来的消息再返回去
	}

	@Override
	public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
    
    
		System.out.println("========异常");
		super.exceptionCaught(ctx, cause);
	}

}

网络传输发来的都是字节数组,但是netty做了封装,默认发来的都是ByteBuf
接下来运行netty启动类的main方法,就启动了一个服务器.
然后用二进制发送接收工具发送即可,就会接到和发送相同的消息.