【Netty】四、Netty服务端推送消息到客户端实现消息个性化推送

你的名字 2023-10-09 15:02 52阅读 0赞

#### Netty服务端推送消息到客户端 ####

*  一、 Netty服务端推送消息到客户端
 *   *  需求：
     *  应用场景
 *  二、服务端代码
 *   *  PushServer
     *  PushServerHandler
     *  PushAckHandler
 *  三、服务端代码
 *   *  PushClient
     *  PushClientHandler
 *  四、测试
 *   *  客户端发送消息
     *  服务端接受消息

## 一、 Netty服务端推送消息到客户端 ##

### 需求： ###

1、服务端从redis或数据库等存储层获取到要推送的消息；  
2、服务端把获取到的消息主动推送给客户端（只要查询到了数据就推送给客户端）；  
3、如果有多个客户端连接到了服务端，要区分客户端，不同客户端发送不同的消息；  
4、客户端接收到消息后给服务端一个应答；  
5、服务端接收到应答之后，对消息状态进行修改，表示该消息已经处理；

### 应用场景 ###

1、个性化推送，可以千人千面，女性用户可以推送化妆品优惠活动消息，男性用户可以推送电子科技类产品消息；  
2、每个客户端（比如手机App），他们首先会登录，登录后有用户的id等唯一业务参数值，用户登录成功后，可以建立一个与netty服务端的长连接并向服务端写出一条信息，信息里面带上用户id等唯一业务参数值；  
3、服务端收到客户端的用户id后，可以用一个全局的Map存放起来:  
Map<String, Map<Integer, Channel>  
Key: channelId, value: (key: userId, value: Channel)  
4、然后服务端启动netty的定时任务，每隔多久从redis或数据库等存储层查询出业务数据，并把数据推送给对应的客户端；  
5、如果连接channel断开了，把全局Map中的channel移除；

## 二、服务端代码 ##

### PushServer ###

import com.mytest.push.handler.PushAckHandler;
    import com.mytest.push.handler.PushServerHandler;
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelFutureListener;
    import io.netty.channel.ChannelInitializer;
    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.serialization.ClassResolvers;
    import io.netty.handler.codec.serialization.ObjectDecoder;
    import io.netty.handler.codec.serialization.ObjectEncoder;
    import io.netty.handler.timeout.IdleStateHandler;
    
    import java.util.concurrent.TimeUnit;
    
    
    /**
     * 服务端向客户端推送消息
     * 
     * 需求：
     * 1、服务端从redis或数据库等存储层获取到要推送的消息；
     * 2、服务端把获取到的消息主动推送给客户端（只要查询到了数据就推送给客户端）；
     * 3、如果有多个客户端连接到了服务端，要区分客户端，不同客户端发送不同的消息；
     * 4、客户端接收到消息后给服务端一个应答；
     * 5、服务端接收到应答之后，对消息状态进行修改，表示该消息已经处理；
     */
    public class PushServer {
        
    
        private static final int PORT = 6868;
    
        public static void main(String[] args) {
        
            PushServer pushServer = new PushServer();
            pushServer.start();
        }
    
        private void start() {
        
            ServerBootstrap serverBootstrap = new ServerBootstrap();
    
            NioEventLoopGroup boosGroup = new NioEventLoopGroup(1);
            NioEventLoopGroup workGroup = new NioEventLoopGroup();
    
            serverBootstrap.group(boosGroup, workGroup);
            serverBootstrap.channel(NioServerSocketChannel.class);
            serverBootstrap.childHandler(new ChannelInitializer<NioSocketChannel>() {
        
                protected void initChannel(NioSocketChannel ch) {
        
                    //ch.pipeline().addLast(new LoggingHandler(LogLevel.INFO));
                    ch.pipeline().addLast(new ObjectEncoder());
                    ch.pipeline().addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.cacheDisabled(null)));
    
                    ch.pipeline().addLast(new IdleStateHandler(30, 0, 0, TimeUnit.SECONDS));
                    ch.pipeline().addLast(PushServerHandler.INSTANCE);
                    ch.pipeline().addLast(PushAckHandler.INSTANCE);
                }
            });
    
            ChannelFuture channelFuture = serverBootstrap.bind(PORT).addListener((ChannelFutureListener) future -> {
        
                if (future.isSuccess()) {
        
                    System.out.println("Netty server start success!");
                } else {
        
                    System.out.println("Netty server start fail!");
                }
            });
            try {
        
                channelFuture.channel().closeFuture().sync();
            } catch (InterruptedException e) {
        
                e.printStackTrace();
            }
        }
    }

### PushServerHandler ###

import com.mytest.codec.LoginMessage;
    import com.mytest.codec.PushAckMessage;
    import com.mytest.codec.PushMessage;
    import io.netty.channel.Channel;
    import io.netty.channel.ChannelHandler;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.ChannelInboundHandlerAdapter;
    import io.netty.handler.timeout.IdleState;
    import io.netty.handler.timeout.IdleStateEvent;
    
    import java.util.Date;
    import java.util.Map;
    import java.util.UUID;
    import java.util.concurrent.ConcurrentHashMap;
    import java.util.concurrent.TimeUnit;
    
    @ChannelHandler.Sharable
    public class PushServerHandler extends ChannelInboundHandlerAdapter {
        
    
        public static final PushServerHandler INSTANCE = new PushServerHandler();
    
        //key = channelID， value =（key：uid， value：channel）
        private static final Map<String, Map<String, Channel>> channelMap = new ConcurrentHashMap<String, Map<String, Channel>>();
    
        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        
            Channel channel = ctx.channel();
            String channelId = channel.id().asLongText();
            Map<String, Channel> uidMap = new ConcurrentHashMap<String, Channel>();
    
            //如果是 LoginMessage
            if (msg instanceof LoginMessage) {
        
                LoginMessage loginMessage = (LoginMessage) msg;
                //当前客户端登录的 用户id --> 当前的channel
                uidMap.put(loginMessage.getUid(), channel);
                channelMap.put(channelId, uidMap);
    
                // 每一条新连接，都是5秒之后发消息
                ctx.executor().scheduleAtFixedRate(() -> {
        
                    String uid = loginMessage.getUid();
    
                    //这样就是每个客户端发送每个客户端的消息
                    Channel ch = channelMap.get(channelId).get(uid);
    
                    if (ch != null) {
        
                        //TODO 可以根据uid查询业务数据，然后把业务数据封装成消息推送给客户端 (业务查询省略)
                        PushMessage pushMessage = new PushMessage();
                        pushMessage.setMessageId(UUID.randomUUID().toString());
                        pushMessage.setContent("尊敬的"+channelId+"童鞋，鉴于你2020年第二季度的卓越表现，公司奖励你1万元，于下月发放，期望再接再厉");
                        pushMessage.setTimestamp(System.currentTimeMillis());
                        pushMessage.setExt(String.valueOf(uid));
    
                        ch.writeAndFlush(pushMessage);
                    }
                    System.out.println(new Date() + " 服务端推送消息ok,currentUid=" + uid + ", channelMap" + channelMap);
                }, 5, 5, TimeUnit.SECONDS);
            }
    
            //如果是 LoginMessage
            if (msg instanceof PushAckMessage) {
        
                PushAckMessage pushAck = (PushAckMessage) msg;
                System.out.println("服务端接收到客户端的确认消息：" + pushAck.getMessageId());
    
            }
        }
    
        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        
            //空闲状态的事件
            if (evt instanceof IdleStateEvent) {
        
                IdleStateEvent event = (IdleStateEvent) evt;
                if (event.state().equals(IdleState.READER_IDLE)) {
        
                    String channelId = ctx.channel().id().asLongText();
                    channelMap.remove(channelId);
    
                    // 心跳包丢失，10秒没有收到客户端心跳 (断开连接)
                    ctx.channel().close().sync();
                    System.out.println("已与 "+ctx.channel().remoteAddress()+" 断开连接");
                }
            }
        }
    
        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        
            String channelId = ctx.channel().id().asLongText();
            channelMap.remove(channelId);
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        
            System.err.println(cause.getMessage());
        }
    }

### PushAckHandler ###

import com.mytest.codec.PushAckMessage;
    import io.netty.channel.ChannelHandler;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.SimpleChannelInboundHandler;
    
    @ChannelHandler.Sharable
    public class PushAckHandler extends SimpleChannelInboundHandler<PushAckMessage> {
        
    
        public static final PushAckHandler INSTANCE = new PushAckHandler();
    
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, PushAckMessage pushAck) {
        
            System.out.println("服务端接收到客户端的确认消息：" + pushAck.getMessageId());
    
            //TODO 更新消息状态 (业务处理，暂时省略)
        }
    }

## 三、服务端代码 ##

### PushClient ###

import com.mytest.codec.LoginMessage;
    import com.mytest.push.handler.PushClientHandler;
    import io.netty.bootstrap.Bootstrap;
    import io.netty.channel.ChannelFuture;
    import io.netty.channel.ChannelInitializer;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioSocketChannel;
    import io.netty.handler.codec.serialization.ClassResolvers;
    import io.netty.handler.codec.serialization.ObjectDecoder;
    import io.netty.handler.codec.serialization.ObjectEncoder;
    import io.netty.handler.timeout.IdleStateHandler;
    import io.netty.util.internal.StringUtil;
    
    import java.util.Scanner;
    import java.util.concurrent.TimeUnit;
    
    
    /**
     * 客户端接收服务端推送的消息
     * 需求：
     * 1、服务端从redis或数据库等存储层获取到要推送的消息；
     * 2、服务端把获取到的消息主动推送给客户端（只要查询到了数据就推送给客户端）；
     * 3、如果有多个客户端连接到了服务端，要区分客户端，不同客户端发送不同的消息；
     * 4、客户端接收到消息后给服务端一个应答；
     * 5、服务端接收到应答之后，对消息状态进行修改，表示该消息已经处理；
     */
    public class PushClient {
        
    
        private static final String HOST = "127.0.0.1";
    
        private static final int PORT = 6868;
    
        public static void main(String[] args) throws Exception {
        
            //假设用户已经登录，登录消息
            LoginMessage loginMessage = new LoginMessage();
            loginMessage.setUid("1000");
    
            PushClient pushClient = new PushClient();
            pushClient.start(loginMessage);
        }
    
        private void start(LoginMessage loginMessage) throws Exception {
        
            Bootstrap bootstrap = new Bootstrap();
            NioEventLoopGroup group = new NioEventLoopGroup();
            bootstrap.group(group);
            bootstrap.channel(NioSocketChannel.class);
            bootstrap.handler(new ChannelInitializer<NioSocketChannel>() {
        
                @Override
                protected void initChannel(NioSocketChannel ch) {
        
                    //ch.pipeline().addLast(new LoggingHandler(LogLevel.INFO));
                    ch.pipeline().addLast(new ObjectEncoder());
                    ch.pipeline().addLast(new ObjectDecoder(Integer.MAX_VALUE, ClassResolvers.cacheDisabled(null)));
                    ch.pipeline().addLast(new IdleStateHandler(0, 10, 0, TimeUnit.SECONDS));
                    ch.pipeline().addLast(PushClientHandler.INSTANCE);
                }
            });
    
            //连netty服务端
            ChannelFuture channelFuture = bootstrap.connect(HOST, PORT).sync();
            if (channelFuture.isSuccess()) {
        
                System.out.println("Connect netty server 成功, 请输入用户ID：");
                //写出登录信息
                Scanner scanner = new Scanner(System.in);
                for (;;) {
        
                    String uid = scanner.nextLine();
                    if (!StringUtil.isNullOrEmpty(uid)) {
        
                        loginMessage.setUid(uid); //业务参数
                        //向服务端写出loginMessage（或者理解成向服务端注册当前app客户端）
                        channelFuture.channel().writeAndFlush(loginMessage);;
                        break;
                    }
                }
            }
            channelFuture.channel().closeFuture().sync();
        }
    }

### PushClientHandler ###

import com.mytest.codec.PushAckMessage;
    import com.mytest.codec.PushMessage;
    import io.netty.channel.ChannelHandler;
    import io.netty.channel.ChannelHandlerContext;
    import io.netty.channel.SimpleChannelInboundHandler;
    import io.netty.handler.timeout.IdleState;
    import io.netty.handler.timeout.IdleStateEvent;
    import io.netty.util.AttributeKey;
    
    import java.util.Date;
    
    @ChannelHandler.Sharable
    public class PushClientHandler extends SimpleChannelInboundHandler<PushMessage> {
        
    
        public static final PushClientHandler INSTANCE = new PushClientHandler();
    
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
        
            ctx.channel().attr(AttributeKey.newInstance("uid")).set(100);
    
            //TODO 重连
        }
    
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, PushMessage msg) {
        
            PushMessage message = (PushMessage) msg;
            System.out.println(new Date() + " 接收到的消息：" + message);
    
            //发送消息确认
            PushAckMessage pushAck = new PushAckMessage();
            pushAck.setMessageId(msg.getMessageId());
            pushAck.setTimestamp(System.currentTimeMillis());
    
            ctx.channel().writeAndFlush(pushAck);
        }
    
        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        
            if (evt instanceof IdleStateEvent) {
        
                if (((IdleStateEvent) evt).state() == IdleState.WRITER_IDLE) {
        
                    ctx.writeAndFlush("ping");
                }
            }
        }
    }

## 四、测试 ##

### 客户端发送消息 ###

![在这里插入图片描述][81f950282d524fe6997b667896d0144d.png]

### 服务端接受消息 ###

![在这里插入图片描述][a3a9f7d1f5aa4296a710896b2b9a888f.png]

[81f950282d524fe6997b667896d0144d.png]: https://img-blog.csdnimg.cn/81f950282d524fe6997b667896d0144d.png
[a3a9f7d1f5aa4296a710896b2b9a888f.png]: https://img-blog.csdnimg.cn/a3a9f7d1f5aa4296a710896b2b9a888f.png