我們在平常項目開發(fā)中，經(jīng)常會用到周期性定時任務，這個時候使用定時任務就能很方便的實現(xiàn)。在SpringBoot中用得最多的就是Schedule。

一、SpringBoot集成Schedule

1、依賴配置

由于Schedule就包含在spring-boot-starter中，所以無需引入其他依賴。

2、啟用定時任務

在啟動類或者配置類上增加@EnableScheduling注解。

import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.scheduling.annotation.EnableScheduling;@EnableScheduling@SpringBootApplicationpublic class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); }}

3、添加定時任務

Schdule支持cron表達式、固定間隔時間、固定頻率三種調度方式。

1）cron表達式定時任務

與Linux下定時任務用到的Cron表達式一樣。

字段 允許值 允許的特殊字符 秒（Seconds） 0~59的整數(shù) , - * / 四個字符 分（Minutes） 0~59的整數(shù) , - * / 四個字符 小時（Hours） 0~23的整數(shù) , - * / 四個字符 日期（DayofMonth） 1~31的整數(shù)（但是你需要考慮該月的天數(shù)） ,- * ? / L W C 八個字符 月份（Month） 1~12的整數(shù)或者 JAN-DEC , - * / 四個字符 星期（DayofWeek） 1~7的整數(shù)或者 SUN-SAT （1=SUN） , - * ? / L C # 八個字符 年(可選，留空)（Year） 1970~2099 , - * / 四個字符

@Component@EnableSchedulingpublic class MyCronTask { private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class); @Scheduled(cron = '0/1 * * * * *') void cronSchedule(){ logger.info('cron schedule execute'); }}

PS：Cron表達式方式配置的定時任務如果其執(zhí)行時間超過調度頻率時，調度器會在下個執(zhí)行周期執(zhí)行。如第一次執(zhí)行從第0秒開始，執(zhí)行時長3秒，則下次執(zhí)行為第4秒。

2）固定間隔定時任務

下一次的任務執(zhí)行時間是從上一次定時任務結束時間開始計算。

@Scheduled(fixedDelay = 2)void fixedDelaySchedule() throws Exception{ Thread.sleep(2000); logger.info('fixed delay schedule execute');}

輸出：

2020-04-23 23:11:54.362 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute2020-04-23 23:11:58.365 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute2020-04-23 23:12:02.372 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute2020-04-23 23:12:06.381 INFO 85325 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed delay schedule execute

3）固定頻率定時任務

按照指定頻率執(zhí)行任務

@Scheduled(fixedRate = 2000)void fixedRateSchedule() throws Exception{ Thread.sleep(3000); logger.info('fixed rate schedule execute');}

輸出：

2020-04-23 23:16:14.750 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute2020-04-23 23:16:17.754 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute2020-04-23 23:16:20.760 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute2020-04-23 23:16:23.760 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute2020-04-23 23:16:26.764 INFO 85328 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : fixed rate schedule execute

PS：當方法的執(zhí)行時間超過任務調度頻率時，調度器會在當前方法執(zhí)行完成后立即執(zhí)行下次任務。

二、配置多個定時任務并發(fā)執(zhí)行

1、并行or串行？

缺省狀態(tài)下，當我們沒有給定時任務配置線程池時，Schedule是串行執(zhí)行，如下：

@Component@EnableSchedulingpublic class MyCronTask { private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class); @Scheduled(fixedDelay = 2000) void task1Schedule() throws Exception{ Thread.sleep(2000); logger.info('task1 execute'); } @Scheduled(fixedDelay = 2000) void task2Schedule() throws Exception{ Thread.sleep(2000); logger.info('task2 execute'); } @Scheduled(fixedDelay = 2000) void task3Schedule() throws Exception{ Thread.sleep(2000); logger.info('task3 execute'); }}

輸出：

2020-04-23 23:19:46.970 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:19:48.973 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:19:50.974 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:19:52.978 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:19:54.984 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:19:56.984 INFO 85332 --- [ scheduling-1] com.springboot.study.tasks.MyCronTask : task3 execute

可以看出來只有一個線程穿行執(zhí)行所有定時任務。

2、Schedule并行執(zhí)行配置

定時調度的并行化，有兩種配置方式：

1）修改任務調度器默認使用的線程池：添加一個configuration，實現(xiàn)SchedulingConfigurer接口就可以了。

@Configurationpublic class ScheduleConfig implements SchedulingConfigurer{ @Override public void configureTasks(ScheduledTaskRegistrar taskRegistrar) { taskRegistrar.setTaskScheduler(getTaskScheduler()); } @Bean public TaskScheduler getTaskScheduler() { ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler(); taskScheduler.setPoolSize(3); taskScheduler.setThreadNamePrefix('myworker-'); taskScheduler.setWaitForTasksToCompleteOnShutdown(true); return taskScheduler; }}

再次執(zhí)行后，輸出：

2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:33:14.197 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:33:18.203 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:33:18.203 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:33:18.204 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-1] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:33:22.208 INFO 85461 --- [ myworker-3] com.springboot.study.tasks.MyCronTask : task1 execute

2）直接將任務交給一步線程池處理：啟用@EnableAsync注解，并在每一個定時任務方法上使用@Async注解。

@Component@EnableScheduling@EnableAsync@Asyncpublic class MyCronTask { private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class); @Scheduled(fixedDelay = 2000) void task1Schedule() throws Exception{ Thread.sleep(2000); logger.info('task1 execute'); } @Scheduled(fixedDelay = 2000) void task2Schedule() throws Exception{ Thread.sleep(2000); logger.info('task2 execute'); } @Scheduled(fixedDelay = 2000) void task3Schedule() throws Exception{ Thread.sleep(2000); logger.info('task3 execute'); }}

輸出如下：

2020-04-23 23:38:00.614 INFO 85468 --- [ task-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:38:00.614 INFO 85468 --- [ task-3] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:38:00.614 INFO 85468 --- [ task-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:38:02.620 INFO 85468 --- [ task-4] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:38:02.620 INFO 85468 --- [ task-5] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:38:02.620 INFO 85468 --- [ task-6] com.springboot.study.tasks.MyCronTask : task3 execute

有上面輸出可以看出來這種方式對于每一次定時任務的執(zhí)行都會創(chuàng)建新的線程，這樣對內存資源是一種浪費，嚴重情況下還會導致服務掛掉，因此為了更好控制線程的使用，我們可以自定義線程池。

首先配置線程池：

@Configurationpublic class MyTaskExecutor { @Bean(name = 'myExecutor') public TaskExecutor getMyExecutor() { ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor(); taskExecutor.setCorePoolSize(3); taskExecutor.setMaxPoolSize(10); taskExecutor.setQueueCapacity(20); taskExecutor.setThreadNamePrefix('myExecutor-'); taskExecutor.initialize(); return taskExecutor; }}

使用我們自己的線程池：

@Component@EnableScheduling@EnableAsync@Async('myExecutor')public class MyCronTask { private static final Logger logger = LoggerFactory.getLogger(MyCronTask.class); @Scheduled(fixedDelay = 2000) void task1Schedule() throws Exception{ Thread.sleep(2000); logger.info('task1 execute'); } @Scheduled(fixedDelay = 2000) void task2Schedule() throws Exception{ Thread.sleep(2000); logger.info('task2 execute'); } @Scheduled(fixedDelay = 2000) void task3Schedule() throws Exception{ Thread.sleep(2000); logger.info('task3 execute'); }}

輸出：

2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:46:47.404 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task3 execute2020-04-23 23:46:49.404 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-2] com.springboot.study.tasks.MyCronTask : task2 execute2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-3] com.springboot.study.tasks.MyCronTask : task1 execute2020-04-23 23:46:51.405 INFO 85488 --- [ myExecutor-1] com.springboot.study.tasks.MyCronTask : task3 execute

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持好吧啦網(wǎng)。