netty框架

netty框架

-NIO的类库和API繁杂，使用麻烦，你需要熟练掌握Selector、ServerSocketChannel、SocketChannel、ByteBuffer等；
- 需要具备其它的额外技能做铺垫，例如熟悉Java多线程编程，因为NIO编程涉及到Reactor模式，你必须对多线程和网路编程非常熟悉，才能编写出高质量的NIO程序；
- 可靠性能力补齐，工作量和难度都非常大。例如客户端面临断连重连、网络闪断、半包读写、失败缓存、网络拥塞和异常码流的处理等等，NIO编程的特点是功能开发相对容易，但是可靠性能力补齐工作量和难度都非常大
- JDK NIO的BUG，例如臭名昭著的epoll bug，它会导致Selector空轮询(在某些场景下select方法会直接返回，即使没有超时并且也没有IO事件到达，这就是著名的epoll bug，这是一个比较严重的bug，它会导致线程陷入死循环，会让CPU飙到100%，极大地影响系统的可靠性，到目前为止，JDK都没有完全解决这个问题)

1. 服务器端代码

package com.car.bigdata.nettyTwo;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class NettyServer {
    public static void main(String[]args) throws InterruptedException {
        NioEventLoopGroup work = new NioEventLoopGroup();
        NioEventLoopGroup boss = new NioEventLoopGroup();
        ServerBootstrap serverBootstrap = new ServerBootstrap();
        serverBootstrap.group(work,boss);
        serverBootstrap.channel(NioServerSocketChannel.class);
        serverBootstrap.childHandler(new ChannelInitializer() {
            @Override
            protected void initChannel(NioSocketChannel ch) throws Exception {
                ChannelPipeline pipeline = ch.pipeline();
                pipeline.addLast(new StringEncoder());
                pipeline.addLast(new StringDecoder());
                pipeline.addLast(new ChannelInboundHandlerAdapter(){
                    @Override
                    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                        //ctx.fireChannelRead(msg);
                        System.out.println("我接收到一条数据");
                        ctx.writeAndFlush(msg);
                    }
                });
            }
        });
        ChannelFuture sync = serverBootstrap.bind(8899).sync();
        ChannelFuture sync1 = sync.channel().closeFuture().sync();
    }
}

3. 客户端代码

package com.car.bigdata.nettyTwo;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.codec.string.StringEncoder;

public class NettyClient {
    public static void main(String[]args) throws InterruptedException {
        NioEventLoopGroup boss = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(boss);
        bootstrap.channel(NioSocketChannel.class);
        bootstrap.handler(new ChannelInitializer() {
            @Override
            protected void initChannel(NioSocketChannel ch) throws Exception {
                ChannelPipeline pipeline = ch.pipeline();
                pipeline.addLast(new StringEncoder());
                pipeline.addLast(new StringDecoder());
                pipeline.addLast(new ChannelInboundHandlerAdapter(){
                    @Override
                    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
                        System.out.println("我接受到服务器的一条消息"+msg);
                    }
                });
            }
        });
        ChannelFuture channelFuture = bootstrap.connect("127.0.0.1",8899).sync();
        channelFuture.channel().writeAndFlush("hello,world!");
        channelFuture.channel().closeFuture().sync();

    }
}