Netty | 工作流程图分析 & 核心组件说明 & 代码案例实践

public class ChannelInboundHandlerAdapter extends ChannelHandlerAdapter implements ChannelInboundHandler {
  //注册事件
    public void channelRegistered(ChannelHandlerContext ctx) ;
  // 
    public void channelUnregistered(ChannelHandlerContext ctx);
  //通道已经就绪
    public void channelActive(ChannelHandlerContext ctx);
    public void channelInactive(ChannelHandlerContext ctx) ;
    //通道读取数据事件
    public void channelRead(ChannelHandlerContext ctx, Object msg) ;
  //通道读取数据事件完毕
    public void channelReadComplete(ChannelHandlerContext ctx) ;
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt);
  //通道可写性已更改
    public void channelWritabilityChanged(ChannelHandlerContext ctx);
  //异常处理
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
}

package com.crush.atguigu.group_chat;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.util.concurrent.GlobalEventExecutor;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
 * @author crush
 */
public class GroupChatServerHandler extends SimpleChannelInboundHandler<String> {
    /**
     * 定义一个channle 组，管理所有的channel
     * GlobalEventExecutor.INSTANCE) 是全局的事件执行器，是一个单例
     */
    private static ChannelGroup channelGroup = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    /**
     * handlerAdded 表示连接建立，一旦连接，第一个被执行
     *              将当前channel 加入到  channelGroup
     * @param ctx
     * @throws Exception
     */
    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        //将该客户加入聊天的信息推送给其它在线的客户端
        /*
        该方法会将 channelGroup 中所有的channel 遍历，并发送 消息，
        我们不需要自己遍历
         */
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 加入聊天" + sdf.format(new java.util.Date()) + " \n");
        channelGroup.add(channel);
    }
    /**
     * 断开连接, 将xx客户离开信息推送给当前在线的客户
     * @param ctx
     * @throws Exception
     */
    @Override
    public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
        Channel channel = ctx.channel();
        channelGroup.writeAndFlush("[客户端]" + channel.remoteAddress() + " 离开了\n");
        System.out.println("channelGroup size" + channelGroup.size());
    }
    /**
     * 表示channel 处于活动状态, 既刚出生 提示 xx上线
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 上线了~");
    }
    /**
     * 表示channel 处于不活动状态, 既死亡状态 提示 xx离线了
     * @param ctx
     * @throws Exception
     */
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        System.out.println(ctx.channel().remoteAddress() + " 离线了~");
    }
    //读取数据
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        //获取到当前channel
        Channel channel = ctx.channel();
        //这时我们遍历channelGroup, 根据不同的情况，回送不同的消息
        channelGroup.forEach(ch -> {
            if (channel != ch) { //不是当前的channel,转发消息
                ch.writeAndFlush("[客户]" + channel.remoteAddress() + " 发送了消息" + msg + "\n");
            } else {//回显自己发送的消息给自己
                ch.writeAndFlush("[自己]发送了消息" + msg + "\n");
            }
        });
    }
    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        //关闭通道
        ctx.close();
    }
}

package com.crush.atguigu.group_chat;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
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;
/**
 * @author crush
 */
public class GroupChatServer {
    /**
     * //监听端口
     */
    private int port;
    public GroupChatServer(int port) {
        this.port = port;
    }
    /**
     * 编写run方法 处理请求
     * @throws Exception
     */
    public void run() throws Exception {
        //创建两个线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup(1);
        //8个NioEventLoop
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            //获取到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //向pipeline加入解码器
                            pipeline.addLast("decoder", new StringDecoder());
                            //向pipeline加入编码器
                            pipeline.addLast("encoder", new StringEncoder());
                            //加入自己的业务处理handler
                            pipeline.addLast(new GroupChatServerHandler());
                        }
                    });
            System.out.println("netty 服务器启动");
            ChannelFuture channelFuture = b.bind(port).sync();
            //监听关闭
            channelFuture.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        new GroupChatServer(7000).run();
    }
}

package com.crush.atguigu.group_chat;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
/**
 * @author crush
 */
public class GroupChatClientHandler extends SimpleChannelInboundHandler<String> {
    //当前Channel 已从对方读取消息时调用。
    @Override
    protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
        System.out.println(msg.trim());
    }
}

package com.crush.atguigu.group_chat;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
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;
import java.util.Scanner;
/**
 * @author crush
 */
public class GroupChatClient {
    private final String host;
    private final int port;
    public GroupChatClient(String host, int port) {
        this.host = host;
        this.port = port;
    }
    public void run() throws Exception {
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap bootstrap = new Bootstrap()
                    .group(group)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            //得到pipeline
                            ChannelPipeline pipeline = ch.pipeline();
                            //加入相关handler
                            pipeline.addLast("decoder", new StringDecoder());
                            pipeline.addLast("encoder", new StringEncoder());
                            //加入自定义的handler
                            pipeline.addLast(new GroupChatClientHandler());
                        }
                    });
            ChannelFuture channelFuture = bootstrap.connect(host, port).sync();
            //得到channel
            Channel channel = channelFuture.channel();
            System.out.println("-------" + channel.localAddress() + "--------");
            //客户端需要输入信息
            Scanner scanner = new Scanner(System.in);
            while (scanner.hasNextLine()) {
                String msg = scanner.nextLine();
                //通过channel 发送到服务器端
                channel.writeAndFlush(msg + "\r\n");
            }
        } finally {
            group.shutdownGracefully();
        }
    }
    public static void main(String[] args) throws Exception {
        new GroupChatClient("127.0.0.1", 7000).run();
    }
}