使用场景
1、下单成功,30分钟未支付。支付超时,自动取消订单
2、订单签收,签收后7天未进行评价。订单超时未评价,系统默认好评
3、下单成功,商家5分钟未接单,订单取消
4、配送超时,推送短信提醒
......
对于延时比较长的场景、实时性不高的场景,我们可以采用任务调度的方式定时轮询处理。如:xxl-job
今天我们采用一种比较简单、轻量级的方式,使用 Redis 
的延迟队列来进行处理。当然有更好的解决方案,可根据公司的技术选型和业务体系选择最优方案。如:使用消息中间件Kafka、RabbitMQ 的延迟队列
先不讨论其实现原理,直接实战上代码先实现基于 Redis 的延迟队列
1、引入 Redisson 依赖
<dependency> <groupId>org.redisson</groupId> 
<artifactId>redisson-spring-boot-starter</artifactId> <version>3.10.5</version> 
</dependency> 
2、Nacos 配置 Redis 连接
spring: redis: host: 127.0.0.1 port: 6379 password: 123456 database: 12 
timeout: 3000 
3、创建 RedissonConfig 配置
/** * Created by LPB on 2020/04/20. */ @Configuration public class 
RedissonConfig { @Value("${spring.redis.host}") private String host; 
@Value("${spring.redis.port}") private int port; 
@Value("${spring.redis.database}") private int database; 
@Value("${spring.redis.password}") private String password; @Bean public 
RedissonClient redissonClient() { Config config = new Config(); 
config.useSingleServer() .setAddress("redis://" + host + ":" + port) 
.setDatabase(database) .setPassword(password); return Redisson.create(config); 
} } 
4、封装 Redis 延迟队列工具类
/** * redis延迟队列工具 * Created by LPB on 2021/04/20. */ @Slf4j @Component public 
class RedisDelayQueueUtil { @Autowired private RedissonClient redissonClient; 
/** * 添加延迟队列 * @param value 队列值 * @param delay 延迟时间 * @param timeUnit 时间单位 * 
@param queueCode 队列键 * @param <T> */ public <T> void addDelayQueue(T value, 
long delay, TimeUnit timeUnit, String queueCode){ try { RBlockingDeque<Object> 
blockingDeque = redissonClient.getBlockingDeque(queueCode); 
RDelayedQueue<Object> delayedQueue = 
redissonClient.getDelayedQueue(blockingDeque); delayedQueue.offer(value, delay, 
timeUnit); log.info("(添加延时队列成功) 队列键:{},队列值:{},延迟时间:{}", queueCode, value, 
timeUnit.toSeconds(delay) + "秒"); } catch (Exception e) { log.error("(添加延时队列失败) 
{}", e.getMessage()); throw new RuntimeException("(添加延时队列失败)"); } } /** * 
获取延迟队列 * @param queueCode * @param <T> * @return * @throws InterruptedException 
*/ public <T> T getDelayQueue(String queueCode) throws InterruptedException { 
RBlockingDeque<Map> blockingDeque = redissonClient.getBlockingDeque(queueCode); 
T value = (T) blockingDeque.take(); return value; } } 
5、创建延迟队列业务枚举
/** * 延迟队列业务枚举 * Created by LPB on 2021/04/20. */ @Getter @NoArgsConstructor 
@AllArgsConstructor public enum RedisDelayQueueEnum { 
ORDER_PAYMENT_TIMEOUT("ORDER_PAYMENT_TIMEOUT","订单支付超时,自动取消订单", 
"orderPaymentTimeout"), 
ORDER_TIMEOUT_NOT_EVALUATED("ORDER_TIMEOUT_NOT_EVALUATED", "订单超时未评价,系统默认好评", 
"orderTimeoutNotEvaluated"); /** * 延迟队列 Redis Key */ private String code; /** * 
中文描述 */ private String name; /** * 延迟队列具体业务实现的 Bean * 可通过 Spring 的上下文获取 */ 
private String beanId; } 
6、定义延迟队列执行器
/** * 延迟队列执行器 * Created by LPB on 2021/04/20. */ public interface 
RedisDelayQueueHandle<T> { void execute(T t); } 
7、创建枚举中定义的Bean,并实现延迟队列执行器
 * OrderPaymentTimeout:订单支付超时延迟队列处理类 /** * 订单支付超时处理类 * Created by LPB on 
2021/04/20. */ @Component @Slf4j public class OrderPaymentTimeout implements 
RedisDelayQueueHandle<Map> { @Override public void execute(Map map) { 
log.info("(收到订单支付超时延迟消息) {}", map); // TODO 订单支付超时,自动取消订单处理业务... } } 
 * OrderTimeoutNotEvaluated:订单超时未评价延迟队列处理类 /** * 订单超时未评价处理类 * Created by LPB 
on 2021/04/20. */ @Component @Slf4j public class OrderTimeoutNotEvaluated 
implements RedisDelayQueueHandle<Map> { @Override public void execute(Map map) 
{ log.info("(收到订单超时未评价延迟消息) {}", map); // TODO 订单超时未评价,系统默认好评处理业务... } } 
8、创建延迟队列消费线程,项目启动完成后开启
/** * 启动延迟队列 * Created by LPB on 2021/04/20. */ @Slf4j @Component public class 
RedisDelayQueueRunner implements CommandLineRunner { @Autowired private 
RedisDelayQueueUtil redisDelayQueueUtil; @Override public void run(String... 
args) { new Thread(() -> { while (true){ try { RedisDelayQueueEnum[] queueEnums 
= RedisDelayQueueEnum.values(); for (RedisDelayQueueEnum queueEnum : 
queueEnums) { Object value = 
redisDelayQueueUtil.getDelayQueue(queueEnum.getCode()); if (value != null) { 
RedisDelayQueueHandle redisDelayQueueHandle = 
SpringUtil.getBean(queueEnum.getBeanId()); 
redisDelayQueueHandle.execute(value); } } } catch (InterruptedException e) { 
log.error("(Redis延迟队列异常中断) {}", e.getMessage()); } } }).start(); 
log.info("(Redis延迟队列启动成功)"); } } 
以上步骤,Redis 延迟队列核心代码已经完成,下面我们写一个测试接口,用 PostMan 模拟测试一下
 
9、创建一个测试接口,模拟添加延迟队列
/** * 延迟队列测试 * Created by LPB on 2020/04/20. */ @RestController public class 
RedisDelayQueueController { @Autowired private RedisDelayQueueUtil 
redisDelayQueueUtil; @PostMapping("/addQueue") public void addQueue() { 
Map<String, String> map1 = new HashMap<>(); map1.put("orderId", "100"); 
map1.put("remark", "订单支付超时,自动取消订单"); Map<String, String> map2 = new 
HashMap<>(); map2.put("orderId", "200"); map2.put("remark", "订单超时未评价,系统默认好评"); 
// 添加订单支付超时,自动取消订单延迟队列。为了测试效果,延迟10秒钟 redisDelayQueueUtil.addDelayQueue(map1, 
10, TimeUnit.SECONDS, RedisDelayQueueEnum.ORDER_PAYMENT_TIMEOUT.getCode()); // 
订单超时未评价,系统默认好评。为了测试效果,延迟20秒钟 redisDelayQueueUtil.addDelayQueue(map2, 20, 
TimeUnit.SECONDS, RedisDelayQueueEnum.ORDER_TIMEOUT_NOT_EVALUATED.getCode()); } 
} 
10、启动 SpringBoot 项目,用 PostMan 调用接口添加延迟队列
 * 通过 Redis 客户端可看到两个延迟队列已添加成功 
 * 查看 IDEA 控制台日志可看到延迟队列已消费成功