延遲隊列的使用場景還比較多，例如：

1、超時未收到支付回調(diào)，主動查詢支付狀態(tài)；

2、規(guī)定時間內(nèi)，訂單未支付，自動取消；

。。。

總之，但凡需要在未來的某個確定的時間點執(zhí)行檢查的場景中都可以用延遲隊列。

常見的手段主要有：定時任務(wù)掃描、RocketMQ延遲隊列、Java自動的延遲隊列、監(jiān)聽Redis Key過期等等

首先，定義一個延遲任務(wù)

package com.cjs.example;import lombok.Data;import java.util.concurrent.Delayed;import java.util.concurrent.TimeUnit;/** * @author ChengJianSheng * @since 2021/3/18 */@Datapublic class DelayTask implements Delayed { private Long orderId; private long expireTime; public DelayTask(Long orderId, long expireTime) { this.orderId = orderId; this.expireTime = expireTime; } @Override public long getDelay(TimeUnit unit) { return expireTime - System.currentTimeMillis(); } @Override public int compareTo(Delayed o) { return (int) (getDelay(TimeUnit.MILLISECONDS) - o.getDelay(TimeUnit.MILLISECONDS)); }}

然后，定義一個管理類

package com.cjs.example;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.CommandLineRunner;import org.springframework.stereotype.Component;import java.util.concurrent.DelayQueue;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * @author ChengJianSheng * @since 2021/3/19 */@Slf4j@Componentpublic class DelayQueueManager implements CommandLineRunner { private DelayQueue<DelayTask> queue = new DelayQueue<>(); @Autowired private ParkOrderQueryHandler handler; @Override public void run(String... strings) throws Exception { ExecutorService executorService = Executors.newSingleThreadExecutor(); executorService.execute(new Runnable() { @Override public void run() { while (true) { try { DelayTask task = queue.take(); handler.handle(task); } catch (InterruptedException e) { e.printStackTrace(); } } } }); } public void put(DelayTask task) { queue.put(task); }}

插入任務(wù)

@Slf4j@Servicepublic class PayServiceImpl implements PayService { @Autowired private DelayQueueManager delayQueueManager; @Override public void pay() { delayQueueManager.put(new DelayTask(1, 15)); delayQueueManager.put(new DelayTask(2, 30)); delayQueueManager.put(new DelayTask(3, 60)); }}2. Redis Key過期回調(diào)

修改redis.conf文件

# bind 127.0.0.1 -::1protected-mode nonotify-keyspace-events Ex

[root@localhost redis-6.2.1]$ src/redis-server redis.conf <?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.4.4</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.example</groupId> <artifactId>demo0401</artifactId> <version>0.0.1-SNAPSHOT</version> <name>demo0401</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build></project>

RedisConfig.java

package com.example.config;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.data.redis.connection.RedisConnectionFactory;import org.springframework.data.redis.listener.RedisMessageListenerContainer;/** * @author ChengJianSheng * @since 2021/4/2 */@Configurationpublic class RedisConfig { @Bean public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) { RedisMessageListenerContainer container = new RedisMessageListenerContainer(); container.setConnectionFactory(connectionFactory); return container; }}

創(chuàng)建一個監(jiān)聽類

package com.example.listener;import org.springframework.data.redis.connection.Message;import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;import org.springframework.data.redis.listener.RedisMessageListenerContainer;import org.springframework.stereotype.Component;/** * @author ChengJianSheng * @since 2021/4/2 */@Componentpublic class MyRedisKeyExpirationListener extends KeyExpirationEventMessageListener { public MyRedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer) { super(listenerContainer); } @Override public void onMessage(Message message, byte[] pattern) { String expiredKey = message.toString(); System.out.println('監(jiān)聽到Key: ' + expiredKey + ' 已過期'); }}3. RocketMQ

官方文檔：https://help.aliyun.com/document_detail/29549.htm

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