Netty学习1(入门demo)

朱雀 2020-11-17 10:31 665阅读 0赞

## 1.定义： ##

> Netty是一个NIO客户端服务器网络框架，用于快速开发可维护性、高性能的网络应用。

## 2. HelloWorld ##

*  一个简单的Netty程序，包含服务器端server和客户端client,下面直接上代码…
 *  1.pom

<dependency>
    			<groupId>io.netty</groupId>
    			<artifactId>netty-all</artifactId>
    			<version>4.1.19.Final</version>
    		</dependency>

*  2.NettyServer
````
    package Netty;
    
    import io.netty.bootstrap.ServerBootstrap;
    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.NioServerSocketChannel;
    import io.netty.handler.codec.string.StringDecoder;
    import io.netty.handler.codec.string.StringEncoder;
    
    import java.net.InetSocketAddress;
    
    public class NettyServer {
    
        public void start(int port){
            EventLoopGroup bossGroup = new NioEventLoopGroup(1);  //boss线程组,接收传入的连接，并将连接分配给worker线程组
            EventLoopGroup workerGroup = new NioEventLoopGroup();
            try {
                ServerBootstrap bootstrap = new ServerBootstrap();
                bootstrap.group(bossGroup,workerGroup)
                         .channel(NioServerSocketChannel.class)      //在这里，我们指定使用NioServerSocketChannel类来实例化一个新的Channel(通道)来接受传入的连接。
                         .childHandler(new ChannelInitializer<SocketChannel>() {  //设置服务器处理程序
                            protected void initChannel(SocketChannel ch) throws Exception {
                                ch.pipeline().addLast("decoder", new StringDecoder());
                                ch.pipeline().addLast("encoder", new StringEncoder());
                                ch.pipeline().addLast(new  NettyServerHandler()); //自定义handler
                            };
                         })
                         .option(ChannelOption.SO_BACKLOG, 128)
                         .childOption(ChannelOption.SO_KEEPALIVE, true);
                ChannelFuture future = bootstrap.bind(port).sync();    //启动服务器
                System.out.println("netty Server port : " + port );
                future.channel().closeFuture().sync();
            } catch (Exception e) {
                bossGroup.shutdownGracefully();
                workerGroup.shutdownGracefully();
            }
        }
    
        public static void main(String[] args) throws Exception {
    
            new NettyServer().start(8081);
        }
    }
````
 *  3.NettyServerHandler:
````
    package Netty;
    
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.ChannelInboundHandlerAdapter;
    
    public class NettyServerHandler extends ChannelInboundHandlerAdapter{
    
       @Override
       public void channelActive(ChannelHandlerContext ctx) throws Exception {
           System.out.println("Netty server 激活...");
        }
    
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
    
            System.out.println("Netty server 接收消息："+ msg);
            ctx.write("hello too");
            ctx.flush();
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    
    }
````
 *  4.NettyClient
````
    package Netty;
    
    import io.netty.bootstrap.Bootstrap;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.ChannelOption;
    import io.netty.channel.ChannelPipeline;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.SocketChannel;
    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 void run(String host,int port) {
            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
                            public void initChannel(SocketChannel ch) throws Exception {
                                ChannelPipeline p = ch.pipeline();
                                p.addLast("decoder", new StringDecoder());
                                p.addLast("encoder", new StringEncoder());
                                p.addLast(new NettyClientHandler());
                            }
                        });
    
                ChannelFuture future = null;
                try {
                    future = b.connect(host, port).sync();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                try {
                    future.channel().closeFuture().sync();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            } finally {
                group.shutdownGracefully();
            }
        }
    
        public static void main(String[] args) throws Exception {
            new NettyClient().run("127.0.0.1",8081);
    
        }
    
    }
````
\-5. NettyClientHandler
````
    package Netty;
    
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.ChannelInboundHandlerAdapter;
    
    public class NettyClientHandler extends ChannelInboundHandlerAdapter{
    
    
        @Override
        public void channelActive(ChannelHandlerContext ctx) {
            System.out.println("netty client 启动...");
            ctx.channel().writeAndFlush("hello lin");
        }
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) {
            System.out.println("netty 服务器响应信息:"+msg);
        }
    
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            cause.printStackTrace();
            ctx.close();
        }
    
    }
````
## 6.Netty 一些主要技术点： ##

bootstrap : netty 客户端程序的引入类  
serverBootstrap：netty 服务端程序的引入类  
channel ： 连接主体  
channelHandler：netty 的处理程序，包括数据的出站、入站、解码、编码、具体业务处理 …功能都在这里完成。  
channelPipeline：存放channelHandler的容器  
EvenLoop：线程，每个channel都会注册到EvenLoop上面执行  
channelFuture：异步执行状态  
解码器：将字节流转换成java对象  
编码器：将java对象转换成字节流