Springboot2 整合 Spring Data Redis 实现消息队列——发布/订阅模式
一般来说，消息队列有两种场景，一种是发布者订阅者模式，一种是生产者消费者模式。
生产者消费者模式：
就像我们用微信和好友（群聊除外）聊天一样，微信就是这个队列，我们可以和很多个好友聊天，但是每条消息只能发给一个好友。
发布者订阅者模式：
发布/订阅模型如图所示，和订阅公众号是一样的。多个消费者可以消费消息。发布者需要建立一个topic 然后消费者去订阅。
接下来用springboot2 + spring data redis 来实现来简单实现订阅者模式:
spring data redis实现发布与订阅需要配置以下信息：
- - Topic
- - MessageListener
- - RedisMessageListenerContainer
1》依赖
<groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.2</version><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.10.0</version></dependency>
Spring Boot支持与三种JSON mapping库集成：Gson、Jackson和JSON-B。Jackson是首选和默认的。
Jackson是spring-boot-starter-json的一部分，spring-boot-starter-web中包含spring-boot-starter-json。也就是说，当项目中引入spring-boot-starter-web后会自动引入spring-boot-starter-json。
但因为我这个项目不是web项目 所以还得引入jackson。如果是web项目就不用引入了。
2》配置 spring data redis:
package com.example.messagingredis;import com.fasterxml.jackson.annotation.JsonAutoDetect;import com.fasterxml.jackson.annotation.PropertyAccessor;import com.fasterxml.jackson.databind.ObjectMapper;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.data.redis.connection.RedisConnectionFactory;import org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory;import org.springframework.data.redis.core.RedisTemplate;import org.springframework.data.redis.listener.ChannelTopic;import org.springframework.data.redis.listener.RedisMessageListenerContainer;import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;import org.springframework.data.redis.serializer.StringRedisSerializer;@Configurationpublic class RedisConfig {@Autowiredprivate LettuceConnectionFactory connectionFactory;@Beanpublic ConsumerRedisListener consumeRedis() {return new ConsumerRedisListener();}@Beanpublic ChannelTopic topic() {return new ChannelTopic("topic");}@Beanpublic RedisMessageListenerContainer redisMessageListenerContainer() {RedisMessageListenerContainer container = new RedisMessageListenerContainer();container.setConnectionFactory(connectionFactory);container.addMessageListener(consumeRedis(), topic());return container;}@Beanpublic RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {RedisTemplate<String, Object> template = new RedisTemplate<String, Object>();template.setConnectionFactory(factory);Jackson2JsonRedisSerializer<Object> jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer<Object>(Object.class);ObjectMapper om = new ObjectMapper();om.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);om.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);jackson2JsonRedisSerializer.setObjectMapper(om);template.setValueSerializer(jackson2JsonRedisSerializer);template.setKeySerializer(new StringRedisSerializer());template.setHashKeySerializer(new StringRedisSerializer());template.afterPropertiesSet();return template;}}
3》实现一个pojo 类型的 topic MessageListener ：
package com.example.messagingredis;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.data.redis.connection.Message;import org.springframework.data.redis.connection.MessageListener;import org.springframework.data.redis.core.RedisTemplate;public class ConsumerRedisListener implements MessageListener {@Autowiredprivate RedisTemplate<String, Object> redisTemplate;@Overridepublic void onMessage(Message message, byte[] pattern) {doBusiness(message);}/*** 打印 message body 内容* @param message*/public void doBusiness(Message message) {Object value = redisTemplate.getValueSerializer().deserialize(message.getBody());System.out.println("consumer message: " + value.toString());}}
实体类：
package com.example.messagingredis;import java.io.Serializable;public class MessageEntity implements Serializable {private static final long serialVersionUID = 8632296967087444509L;private String id;private String content;public MessageEntity() {super();}public MessageEntity(String id, String content) {super();this.id = id;this.content = content;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}@Overridepublic String toString() {return "MessageEntity [id=" + id + ", content=" + content + "]";}}
4》其它：
记得配置上 redis 相关的配置，最简单的application.properties配置如下：
spring.redis.host=127.0.0.1
spring.redis.port=6379
5》添加测试类：
package com.example.messagingredis;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.context.ApplicationContext;import org.springframework.data.redis.connection.RedisConnectionFactory;import org.springframework.data.redis.core.RedisTemplate;import java.util.Date;@SpringBootApplicationpublic class MessagingRedisApplication {public static void main(String[] args) {ApplicationContext ctx = SpringApplication.run(MessagingRedisApplication.class, args);RedisConfig template = ctx.getBean(RedisConfig.class);RedisConnectionFactory factory = null;RedisTemplate<String,Object> redisTemplate = template.redisTemplate(factory);String channel = "topic";redisTemplate.convertAndSend(channel, "hello world");redisTemplate.convertAndSend(channel, new Date(System.currentTimeMillis()));redisTemplate.convertAndSend(channel, new MessageEntity("1", "object"));}}
执行可以看到控制台有订阅者消费消息打印出来
最后总结下：
用 spring data redis 来实现 redis 订阅者，本质上还是Listener模式，只需要配置Topic, MessageListener 和 RedisMessageListenerContainer就可以了。（就是redisconfig里面的配置）同时，发布时，只需要使用 redisTemplate 的 convertAndSend方法即可topic来发布message。
参考：https://my.oschina.net/simonton/blog/1833775
https://blog.csdn.net/johnf_nash/article/details/87891293
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