3.1、基于 Pub/Sub 的队列

• 消息可以重复消费，多个消费者订阅同一频道即可

• 一个消费者根据匹配规则订阅多个频道

• 消费者只能消费订阅之后发布的消息，这意味着，消费者下线再上线这期间发布的消息将会丢失

• 数据不具有持久化。同样Redis宕机也会数据丢失

• 消息发布后，是推送到一个缓冲区(内存)，消费者从缓冲区拉取消息，当消息堆积，缓冲区溢出，消费者就会被迫下线，同时释放对应的缓冲区；

RedisConfig 中添加监听器

    /**
     * redis消息监听器容器
     */
    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);

        //订阅频道，通配符*表示任意多个占位符
        container.addMessageListener(new MySubscribe(), new PatternTopic("channel*"));

        return container;
    }

订阅者

import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.connection.MessageListener;

public class MySubscribe implements MessageListener {

    @Override
    public void onMessage(Message message, byte[] bytes) {
        System.out.println("订阅频道:" + new String(message.getChannel()));
        System.out.println("接收数据:" + new String(message.getBody()));
    }
}

消息发布

@GetMapping("/publish")
public void publish() {
    redisTemplate.convertAndSend("channel_first", "hello world");
}

另一种发布方式

    /**
     * redis消息监听器容器
     */
    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);

        //订阅频道，通配符*表示任意多个占位符
        container.addMessageListener(new MySubscribe(), new PatternTopic("channel*"));
        // 通配符?：表示一个占位符
        MessageListenerAdapter listenerAdapter = new MessageListenerAdapter(new MySubscribe2(), "getMessage");
        listenerAdapter.afterPropertiesSet();
        container.addMessageListener(listenerAdapter, new PatternTopic("channel?"));

        return container;
    }

public class MySubscribe2 {

    public void getMessage(Object message, String channel) {
        System.out.println("订阅频道2:" + channel);
        System.out.println("接收数据2:" + message);
    }
}

    @GetMapping("/publish2")
    public void publish2() {
        redisTemplate.convertAndSend("channel2", "hello world");
    }

消息是实体对象，进行转换

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class User implements Serializable {
    private static final long serialVersionUID = 5250232737975907491L;
    private Integer id;
    private String username;
}

public class MySubscribe3 implements MessageListener {

    @Override
    public void onMessage(Message message, byte[] bytes) {
        Jackson2JsonRedisSerializer<User> jacksonSerializer = new Jackson2JsonRedisSerializer<>(User.class);
        jacksonSerializer.setObjectMapper(ObjectMapperConfig.objectMapper);
        User user = jacksonSerializer.deserialize(message.getBody());

        System.out.println("订阅频道3:" + new String(message.getChannel()));
        System.out.println("接收数据3:" + user);
    }
}

    /**
     * redis消息监听器容器
     */
    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);

        //订阅频道，通配符*：表示任意多个占位符
        container.addMessageListener(new MySubscribe(), new PatternTopic("channel*"));
        // 通配符?：表示一个占位符
        MessageListenerAdapter listenerAdapter = new MessageListenerAdapter(new MySubscribe2(), "getMessage");
        listenerAdapter.afterPropertiesSet();
        container.addMessageListener(listenerAdapter, new PatternTopic("channel?"));

        container.addMessageListener(new MySubscribe3(), new PatternTopic("user"));

        return container;
    }

    /**
     * redis消息监听器容器
     */
    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);

        //订阅频道，通配符*：表示任意多个占位符
        container.addMessageListener(new MySubscribe(), new PatternTopic("channel*"));
        // 通配符?：表示一个占位符
        MessageListenerAdapter listenerAdapter = new MessageListenerAdapter(new MySubscribe2(), "getMessage");
        listenerAdapter.afterPropertiesSet();
        container.addMessageListener(listenerAdapter, new PatternTopic("channel?"));

        container.addMessageListener(new MySubscribe3(), new PatternTopic("user"));

        return container;
    }

   @GetMapping("/publish3")
    public void publish3() {
        User user = User.builder().id(1).username("yzm").build();
        redisTemplate.convertAndSend("user", user);
    }