Java 延迟队列的常用的实现方式_Java教程

延迟队列的使用场景还比较多，例如：

1、超时未收到支付回调，主动查询支付状态；

2、规定时间内，订单未支付，自动取消；

。。。

总之，但凡需要在未来的某个确定的时间点执行检查的场景中都可以用延迟队列。

常见的手段主要有：定时任务扫描、RocketMQ延迟队列、Java自动的延迟队列、监听Redis Key过期等等

1. DelayQueue

首先，定义一个延迟任务

package com.cjs.example;
import lombok.Data;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
/**
* @author ChengJianSheng
* @since 2021/3/18
*/
@Data
public 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，定义一个管理类

插入任务

修改redis.conf文件

# bind 127.0.0.1 -::1
protected-mode no
notify-keyspace-events Ex

Java 延迟队列的常用的实现方式

[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/>
</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
*/
@Configuration
public class RedisConfig {
@Bean
public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {
RedisMessageListenerContainer container = new RedisMessageListenerContainer();
container.setConnectionFactory(connectionFactory);
return container;
}
}

创建一个监听类

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
*/
@Component
public 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("监听到Key: " + expiredKey + " 已过期");
}
}