RabbitMQ实践——搭建单人聊天服务

大纲

创建Core交换器
用户登录
发起聊天邀请
接受邀请
聊天
实验过程
总结
代码工程

经过之前的若干节的学习，我们基本掌握了Rabbitmq各个组件和功能。本文我们将使用之前的知识搭建一个简单的单人聊天服务。
基本结构如下。为了避免Server有太多连线导致杂乱，下图将Server画成两个模块，实则是一个服务。
在这里插入图片描述
该服务由两个核心交换器构成。
Core交换器是服务启动时创建的，它主要是为了向不同用户传递“系统通知型”消息。比如Jerry向Tom发起聊天邀请，则是通过上面黑色字体6-10的流程发给了Core交换器。然后Core交换器将该条消息告知Tom。
Fanout交换器是用来消息传递的。Jerry和Tom都向其发送消息，然后路由到两个队列。它们两各自订阅一个队列，就可以看到彼此的聊天内容了。

创建Core交换器

package com.rabbitmq.chat.service;

import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;

import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageListener;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import jakarta.annotation.PostConstruct;
import reactor.core.publisher.Flux;

@Service
public class Core {
    @Autowired
    private RabbitTemplate rabbitTemplate;
    private ConnectionFactory connectionFactory;

    final String exchangeName = "Core";

    @PostConstruct
    public void init() {
        connectionFactory = rabbitTemplate.getConnectionFactory();
        createExchange(exchangeName);
    }

    private void createExchange(String exchangeName) {
        rabbitTemplate.execute(channel -> {
            channel.exchangeDeclare(exchangeName, "direct", false, true, null);
            return null;
        });
    }

用户登录

用户登录后，我们会创建一个“系统通知”队列。然后用户就会通过长连接形式，持续等待系统发出通知。

    private final ReentrantLock lock = new ReentrantLock();
    final private Map<String, SimpleMessageListenerContainer> listeners = new java.util.HashMap<>();
    
    public Flux<String> Login(String username) {
        createExclusiveQueue(username);
        createBanding(exchangeName, username, username);
        return Flux.create(emitter -> {
           SimpleMessageListenerContainer container = getListener(username, (Message message) -> {
               String msg = new String(message.getBody());
               System.out.println("Received message: " + msg);
               emitter.next(msg);
           });
           container.start();
       });
    }
 
     private void createExchange(String exchangeName) {
        rabbitTemplate.execute(channel -> {
            channel.exchangeDeclare(exchangeName, "direct", false, true, null);
            return null;
        });
    }

    private void createBanding(String exchangeName, String queueName, String routingKey) {
        rabbitTemplate.execute(channel -> {
            channel.queueBind(queueName, exchangeName, routingKey);
            return null;
        });
    }
    
    private SimpleMessageListenerContainer getListener(String queueName, MessageListener messageListener) {
        lock.lock();
        try {
            SimpleMessageListenerContainer listener = listeners.get(queueName);
            if (listener == null && messageListener != null) {
                listener = new SimpleMessageListenerContainer();
                listener.setConnectionFactory(connectionFactory);
                listener.setQueueNames(queueName);
                listener.setMessageListener(messageListener);
                listeners.put(queueName, listener);
            }
            return listener;
        } finally {
            lock.unlock();
        }
    }

Controller如下

package com.rabbitmq.chat.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.rabbitmq.chat.service.Core;

import reactor.core.publisher.Flux;

@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private Core core;

    @PostMapping(value = "/login", produces = "text/event-stream")
    public Flux<String> login(@RequestParam String username) {
        return core.Login(username);
    }
}

发起聊天邀请

发起聊天邀请时，系统会预先创建一个聊天室（ChatRoomInfo ）。它包含上图中Fanout交换器、以及聊天双方需要订阅的消息队列。
这些创建完后，发起方就会等待对方发送的消息，也可以自己和自己聊天。因为消息队列已经创建好了，只是对方还没使用。

package com.rabbitmq.chat.service;

import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;

import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import jakarta.annotation.PostConstruct;
import lombok.Data;
import reactor.core.publisher.Flux;

@Service
public class ChatRoom {
    @Autowired
    private RabbitTemplate rabbitTemplate;
    private ConnectionFactory connectionFactory;

    @Data
    private class ChatRoomInfo {
        private String exchange;
        private Map<String, String> usernameToQueuename;
    }

    private final Map<String, ChatRoomInfo> chatRooms = new java.util.HashMap<>();
    private final ReentrantLock lock = new ReentrantLock();   
    
    @PostConstruct
    public void init() {
        connectionFactory = rabbitTemplate.getConnectionFactory();
    }

    public Flux<String> invite(String fromUsername, String toUsername) {
        String chatRoomName = getChatRoomName(fromUsername, toUsername);
        ChatRoomInfo chatRoomInfo = chatRooms.get(chatRoomName);
        if (chatRoomInfo == null) {
            createChatRoom(fromUsername, toUsername);
        }
        return talk(chatRoomName, fromUsername);
    }
    
    private void createChatRoom(String fromUsername, String toUsername) {
        String chatRoomName = getChatRoomName(fromUsername, toUsername);
        String exchangeName = chatRoomName;
        String fromQueueName = "queue-" + fromUsername + "-" + toUsername;
        String toQueueName = "queue-" + toUsername + "-" + fromUsername;
        
        rabbitTemplate.execute(action -> {
            action.exchangeDeclare(exchangeName, "fanout", false, true, null);
            action.queueDeclare(fromQueueName, false, true, false, null);
            action.queueDeclare(toQueueName, false, true, false, null);
            action.queueBind(fromQueueName, exchangeName, "");
            action.queueBind(toQueueName, exchangeName, "");
            return null;
        });

        lock.lock();
        try {
            ChatRoomInfo chatRoomInfo = new ChatRoomInfo();
            chatRoomInfo.setExchange(exchangeName);
            chatRoomInfo.setUsernameToQueuename(Map.of(fromUsername, fromQueueName, toUsername, toQueueName));
            chatRooms.put(chatRoomName, chatRoomInfo);
        } finally {
            lock.unlock();
        }
    }

接受邀请

被邀请方通过Core交换器得知有人要和它聊天。
然后接受邀请的请求会寻找聊天室信息，然后订阅聊天记录队列。

    public Flux<String> accept(String fromUsername, String toUsername) {
        String chatRoomName = getChatRoomName(fromUsername, toUsername);
        return talk(chatRoomName, toUsername);
    }

    private Flux<String> talk(String chatRoomName, String username) {
        ChatRoomInfo chatRoomInfo = chatRooms.get(chatRoomName);
        if (chatRoomInfo == null) {
            throw new IllegalArgumentException("Chat room not found");
        }
        String queueName = chatRoomInfo.getUsernameToQueuename().get(username);
        return Flux.create(emitter -> {
            SimpleMessageListenerContainer listener = new SimpleMessageListenerContainer();
            listener.setConnectionFactory(connectionFactory);
            listener.setQueueNames(queueName);
            listener.setMessageListener((Message message) -> {
                String msg = new String(message.getBody());
                System.out.println(username + " received message: " + msg);
                emitter.next(msg);
            });
            listener.start();
        });
    }

聊天

聊天的逻辑就是找到聊天室信息，然后向交换器发送消息。

    public void chat(String fromUsername, String toUsername, String message) {
        String chatRoomName = getChatRoomName(fromUsername, toUsername);
        ChatRoomInfo chatRoomInfo = chatRooms.get(chatRoomName);
        if (chatRoomInfo == null) {
            chatRoomName = getChatRoomName(toUsername, fromUsername);
            chatRoomInfo = chatRooms.get(chatRoomName);
        }
        if (chatRoomInfo == null) {
            throw new IllegalArgumentException("Chat room not found");
        }
        rabbitTemplate.convertAndSend(chatRoomInfo.getExchange(), "", fromUsername + ": " + message);
    }
    
    private String getChatRoomName(String fromUsername, String toUsername) {
        return fromUsername + "-" + toUsername + "-chat-room";
    }

Controller侧代码

package com.rabbitmq.chat.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.rabbitmq.chat.service.ChatRoom;
import com.rabbitmq.chat.service.Core;

import reactor.core.publisher.Flux;

@RestController
@RequestMapping("/chat")
public class ChatController {
    @Autowired
    private Core core;

    @Autowired
    private ChatRoom chatRoom;

    @PutMapping(value = "/invite", produces = "text/event-stream")
    public Flux<String> invite(@RequestParam String fromUsername, @RequestParam String toUsername) {
        core.invite(fromUsername, toUsername);
        return chatRoom.invite(fromUsername, toUsername);
    }

    @PutMapping(value = "/accept", produces = "text/event-stream")
    public Flux<String> accept(@RequestParam String fromUsername, @RequestParam String toUsername) {
        core.accept(fromUsername, toUsername);
        return chatRoom.accept(fromUsername, toUsername);
    }

    @PostMapping("/send")
    public void send(@RequestParam String fromUsername, @RequestParam String toUsername, @RequestParam String message) {
        chatRoom.chat(fromUsername, toUsername, message);
    }
}

实验过程

在Postman中，我们先让tom登录，然后jerry登录。
在这里插入图片描述

在后台，我们看到创建两个队列

以及Core交换器的绑定关系也被更新

Jerry向Tom发起聊天邀请

可以看到Tom收到了邀请

同时新增了两个队列

以及一个交换器

Tom通过下面请求接受邀请

Jerry收到Tom接受了邀请的通知
在这里插入图片描述
后面它们就可以聊天了

它们的聊天窗口都收到了消息