What is Redis publish and subscribe?

I thought of using the Redis subscription publishing model to solve the push problem~.

For the conceptual description, I still need to mention it more or less:

什么是Redis发布订阅？Redis发布订阅是一种消息通信模式，发送者通过通道A发送消息message,订阅过通道A的客户端就可以接收到消息message。嗯度娘上面的解释要比我所说的好多了，而我所理解的就是：所谓的订阅发布模式，其实和我们看电视，听广播差不多，在我们没有调台（换频道）的时候，那个频道也是在传递消息的（发布）。我们换到那个频道上（订阅）就能接收到消息了。是的，虽然可能有些不恰当～

Explanation

本文中示例采用了三个客户端，以“品”字形排列，由上至下，由左至右分别为客户端1(c1)，客户端2(c2)，客户端3(c3).特此说明。

Redis subscription and publishing commands

First of all, declare, Regarding the construction of the Redis server, please check the relevant information by yourself to build the environment

I heard that there are only 6 simple commands for publishing and subscribing in Redis. That is:

• PSUBSCRIBE pattern [pattern ...]

• Subscribe to one or more channels that match the pattern format

• PUBLISH channel message

• Publish message to chanel

• PUBSUB subcommand [argument [argument ...]]

• View subscription and publishing system status

• PUNSUBSCRIBE [pattern [pattern ...]]

• Unsubscribe from all channels that match the format

• SUBSCRIBE channel [channel ...]

• Subscribe to one or more channels

• UNSUBSCRIBE [channel [channel ...]]

• Unsubscribe channel

---

##Example 1 - SUBSCRIBE

After connecting to redis, type the command

SUBSCRIBE study

to subscribe to a channel named study.

The study channel will send a message next. ~~

---

Example 2 - PUBLISH

Open another client. I use the top one in the glyph layout as the publisher, type

PUBLISH study "message1-go go go"

It can be seen that when client 1 publishes a message in the study channel, client 2 (subscribed to the study channel) can receive the message published by c1, while client 3 cannot receive the message sent by c1 because it has not subscribed to the study channel. information.

---

Example 3 - PSUBSCRIBE

Now, follow the blogger’s left hand and right hand in slow motion. Type

PSUBSCRIBE study*

OK in c3, now type

PUBLISH study "message2"

in c1. The above result picture:

c3 adopts the form of wildcard, and the study channel is also successfully subscribed. .

Next, continue typing the command in c1:

PUBLISH study:java "I hate java forever"

You can see that using psubscribe not only subscribes to the study channel, but also subscribes to the channel headed by study.

---

Example 4 - PUBSUB

Type pubsub channel in c1, you can get:

127.0.0.1:6379> PUBSUB channels

1) "study"

means the currently active channel.

---

Jedis implements the subscription publisher mode

好了，上面通过命令行熟悉了一下Redis中有关订阅发布者模式的相关命令。下面我们要将redis的订阅与发布者嵌入到项目中。

首先，我们使用jedis先订阅一个名为：study的频道

Then we first publish the message from the command line:

After that, we use jedis to publish the message in the project ：

We can have normal communication~Oh yeah~

---

Core code:

PublishMessage.java is used to start a thread to publish messages

private Logger logger = LoggerFactory.getLogger(PublishMessage.class);

@Resource
private JedisCluster jedisCluster;

/**
 * 发布消息
 *
 * @param channel 频道
 * @param message 信息
 */
public void sendMessage(final String channel, final String message) {
    Thread thread = new Thread(() -> {
        Long publish = jedisCluster.publish(channel, message);
        logger.info("服务器在: {} 频道发布消息{} - {}", channel, message, publish);
    });
    logger.info("发布线程启动:");
    thread.setName("publishThread");
    thread.start();
}

ChatSubscribe.java is used to handle subscription-related events, inherited from JedisPubSub

private Logger logger = LoggerFactory.getLogger(ChatSubscribe.class);

// 取得订阅的消息后的处理
@Override
public void onMessage(String channel, String message) {
    logger.info("订阅成功,接收到的消息为:频道-{},消息-{}", channel, message);
    RedisString.message = message;
}

// 取得按表达式的方式订阅的消息后的处理
@Override
public void onPMessage(String pattern, String channel, String message) {
    System.out.println("-----取得按表达式的方式订阅的消息后的处理-----");
    System.out.println(pattern + "=" + channel + "=" + message);
}

// 初始化按表达式的方式订阅时候的处理
@Override
public void onPSubscribe(String pattern, int subscribedChannels) {
    System.out.println("-----初始化按表达式的方式订阅时候的处理-----");
    System.out.println(pattern + "=" + subscribedChannels);
}

// 取消按表达式的方式订阅时候的处理
@Override
public void onPUnsubscribe(String pattern, int subscribedChannels) {
    System.out.println("-----取消按表达式的方式订阅时候的处理-----");
    System.out.println(pattern + "=" + subscribedChannels);
}

@Override
public void onPong(String pattern) {
    super.onPong(pattern);
}

// 初始化订阅时候的处理
@Override
public void onSubscribe(String channel, int subscribedChannels) {
    logger.info("初始化订阅信息:频道-{},订阅频道-{}", channel, subscribedChannels);
}

// 取消订阅时候的处理
@Override
public void onUnsubscribe(String channel, int subscribedChannels) {
    logger.info("已取消订阅频道{}", channel);
}

SubScribeMessage.java subscribing to channels, canceling channels and other action classes

private Logger logger = LoggerFactory.getLogger(SubScribeMessage.class);

private ExecutorService cachedThreadPool = Executors.newCachedThreadPool();

@Resource
private JedisCluster jedisCluster;
/**
     * 订阅频道
     *
     * @param channel          频道
     * @param roomSubListerner
     */
    public void subscribeChannel(final String channel, final ChatSubscribe roomSubListerner) {

        cachedThreadPool.execute(new Runnable() {
            @Override
            public void run() {
                jedisCluster.subscribe(roomSubListerner, channel);
            }
        });
    }

jedisCluster是否封装工具类，取自各位看官，核心代码已给出，请各位看官根据自身业务与逻辑，自行更改与优化代码。

本次示例程序采用tomcat 9.0 + spring + springmvc

使用了诸如：@RestController,@GetMapping等相关注解，便于开发，有兴趣可自行查阅spring相关资料。

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