十.Netty入门到超神系列-基于Netty群聊系统

素颜马尾好姑娘i 2022-09-05 00:13 127阅读 0赞

# 前言 #

本章节基于Netty做一个聊天室案例加强Netty的熟练度，案例的效果是服务端可以广播某客户端的消息给所有客户端。每个客户端监听键盘输入来获取消息，然后发送给服务端。

# 服务端 #

服务端一样的需要创建BossGroup 和 WorkGroup , 然后使用ServerBootStrap 来配置Netty和启动Netty。

public class NettyGroupChatServer { 
    
        public static void main(String[] args) { 
            new NettyGroupChatServer().start();
        }
    
        //监听
       public void start(){ 
            //循环组
           NioEventLoopGroup bossGroup = new NioEventLoopGroup();
           NioEventLoopGroup workGroup = new NioEventLoopGroup();
           //启动引导
           ServerBootstrap bootstrap = new ServerBootstrap();
           //Netty配置
           bootstrap.group(bossGroup,workGroup)
                   .option(ChannelOption.SO_BACKLOG,32)
                   .childOption(ChannelOption.SO_KEEPALIVE,true)
                   .channel(NioServerSocketChannel.class)
                   .childHandler(new ChannelInitializer<SocketChannel>() { 
                       @Override
                       protected void initChannel(SocketChannel channel) throws Exception { 
                           //解码器
                           channel.pipeline().addLast("decoder", new StringDecoder());
                           //编码器
                           channel.pipeline().addLast("encoder",new StringEncoder());
                           //处理器
                           channel.pipeline().addLast("nettyGroupChatHandler",new NettyGroupChatServerHandler());
                       }
                   });
    
           try { 
               //启动服务
               ChannelFuture future = bootstrap.bind(new InetSocketAddress("127.0.0.1", 8888)).sync();
               future.channel().closeFuture().sync();
           } catch (InterruptedException e) { 
               e.printStackTrace();
           }finally { 
               //关闭资源
               bossGroup.shutdownGracefully();
               workGroup.shutdownGracefully();
           }
       }
    
    }

服务端处理器我们通过继承 SimpleChannelInboundHandler 入站Handler来处理消息。其中提供了几个方法

*  channelRead0 ：读取消息
 *  handlerRemoved ：客户端断开
 *  handlerAdded ：客户端建立连接
 *  exceptionCaught ：出现异常

具体代码如下

public class NettyGroupChatServerHandler extends SimpleChannelInboundHandler<String> { 
    
        //把所有客户端的channel保存起来
        private static ChannelGroup channels = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);
        private static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception { 
            String message = dateFormat.format(new Date())+":%s:"+msg;
            //消息转发给所有的客户端
            channels.forEach(channel -> { 
                if(channel == ctx.channel()){ 
                    String sendMsg = String.format(message, "我");
                    channel.writeAndFlush(sendMsg);
                    System.out.println(sendMsg);
    
                }else{ 
                    String sendMsg = String.format(message, ctx.channel().remoteAddress());
                    channel.writeAndFlush(sendMsg);
                    System.out.println(sendMsg);
                }
            });
        }
    
        //断开连接 , 把消息广播给其他客户端
        @Override
        public void handlerRemoved(ChannelHandlerContext ctx) throws Exception { 
            String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":断开连接";
            channels.writeAndFlush(message);
            System.out.println(message);
        }
    
        //建立连接
        @Override
        public void handlerAdded(ChannelHandlerContext ctx) throws Exception { 
            String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":加入聊天室";
            //自动把消息广播给其客户端
            channels.writeAndFlush(message);
            //客户端加入组
            channels.add(ctx.channel());
            System.out.println(message);
        }
    
        //出现异常
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { 
            ctx.channel().close();
        }
    
        //客户端退出
        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception { 
            String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":退出聊天室";
            System.out.println(message);
        }
    
        //客户端出于活动
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception { 
            String message = dateFormat.format(new Date())+":"+ctx.channel().remoteAddress()+":上线啦";
            System.out.println(message);
        }
    }

# 客户端 #

客户端需要创建一个循环事件组，然后通过BootStrap去启动,然后扫描键盘输入作为数据源来把信息发送给服务端

public class NettyGroupChatClient { 
    
        public static void main(String[] args) { 
            new NettyGroupChatClient().start();
        }
        public void start(){ 
            NioEventLoopGroup eventLoopGroup = new NioEventLoopGroup();
            Bootstrap bootstrap = new Bootstrap();
    
            bootstrap.group(eventLoopGroup)
                    .channel(NioSocketChannel.class)
                    .handler(new ChannelInitializer<SocketChannel>() { 
    
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception { 
                            //解码器
                            channel.pipeline().addLast("decoder", new StringDecoder());
                            //编码器
                            channel.pipeline().addLast("encoder",new StringEncoder());
                            //处理器
                            channel.pipeline().addLast("nettyGroupChatClientHandler",new NettyGroupChatClientHandler());
                        }
                    });
            try { 
                ChannelFuture future = bootstrap.connect(new InetSocketAddress("127.0.0.1", 8888)).sync();
                //通道
                Channel channel = future.channel();
                //扫描键盘输入
                Scanner scanner = new Scanner(System.in);
                while(scanner.hasNextLine()){ 
                    String message = scanner.nextLine();
                    //发送数据
                    channel.writeAndFlush(message);
                }
            } catch (InterruptedException e) { 
            }finally { 
                eventLoopGroup.shutdownGracefully();
            }
        }
    }

对于处理器只需要接收服务端转发过来的消息即可

public class NettyGroupChatClientHandler extends SimpleChannelInboundHandler<String> { 
    
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception { 
            System.out.println(msg);
        }
    }

启动服务端和多个客户端，效果如下  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0OTQxNDg_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0OTQxNDg_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][ce9ca4de23ac4a5bb7d420dd6758dfcd.png]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0OTQxNDg_size_16_color_FFFFFF_t_70 1]: /images/20220829/c9e7ba7617fd480d999f1ba544ea483f.png
[ce9ca4de23ac4a5bb7d420dd6758dfcd.png]: /images/20220829/efead5c2ef724a20820dd86d4782a666.png