在Spring Boot项目中，可以通过@EnableScheduling注解和@Scheduled注解实现定时任务（在DD的Spring Boot教程中就有介绍：使用@Scheduled实现定时任务
），也可以通过SchedulingConfigurer接口来实现定时任务。但是这两种方式不能动态添加、删除、启动、停止任务。
下面是DD在简书上看到的一篇非常不错的文章，作者jessehua，通过扩展Spring自带的定时任务，实现了定时任务的动态增删启停。如果你也有这样的需求，那么可以看看下面的内容，学习一下作者的思路。
要实现动态增删启停定时任务功能，比较广泛的做法是集成Quartz框架。但是本人的开发原则是：在满足项目需求的情况下，尽量少的依赖其它框架，避免项目过于臃肿和复杂。
查看spring-context这个jar包中org.springframework.scheduling.ScheduledTaskRegistrar这个类的源代码，发现可以通过改造这个类就能实现动态增删启停定时任务功能。
添加执行定时任务的线程池配置类:
@Configuration public class SchedulingConfig { @Bean public TaskScheduler taskScheduler() { ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler(); // 定时任务执行线程池核心线程数 taskScheduler.setPoolSize(4); taskScheduler.setRemoveOnCancelPolicy(true); taskScheduler.setThreadNamePrefix("TaskSchedulerThreadPool-"); return taskScheduler; } }
添加ScheduledFuture的包装类。ScheduledFuture是ScheduledExecutorService定时任务线程池的执行结果。
public final class ScheduledTask { volatile ScheduledFuture<?> future; /** * 取消定时任务 */ public void cancel() { ScheduledFuture<?> future = this.future; if (future != null) { future.cancel(true); } } }
添加Runnable接口实现类，被定时任务线程池调用，用来执行指定bean里面的方法。
public class SchedulingRunnable implements Runnable { private static final Logger logger = LoggerFactory.getLogger(SchedulingRunnable.class); private String beanName; private String methodName; private String params; public SchedulingRunnable(String beanName, String methodName) { this(beanName, methodName, null); } public SchedulingRunnable(String beanName, String methodName, String params) { this.beanName = beanName; this.methodName = methodName; this.params = params; } @Override public void run() { logger.info("定时任务开始执行 - bean：{}，方法：{}，参数：{}", beanName, methodName, params); long startTime = System.currentTimeMillis(); try { Object target = SpringContextUtils.getBean(beanName); Method method = null; if (StringUtils.isNotEmpty(params)) { method = target.getClass().getDeclaredMethod(methodName, String.class); } else { method = target.getClass().getDeclaredMethod(methodName); } ReflectionUtils.makeAccessible(method); if (StringUtils.isNotEmpty(params)) { method.invoke(target, params); } else { method.invoke(target); } } catch (Exception ex) { logger.error(String.format("定时任务执行异常 - bean：%s，方法：%s，参数：%s ", beanName, methodName, params), ex); } long times = System.currentTimeMillis() - startTime; logger.info("定时任务执行结束 - bean：{}，方法：{}，参数：{}，耗时：{} 毫秒", beanName, methodName, params, times); } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; SchedulingRunnable that = (SchedulingRunnable) o; if (params == null) { return beanName.equals(that.beanName) && methodName.equals(that.methodName) && that.params == null; } return beanName.equals(that.beanName) && methodName.equals(that.methodName) && params.equals(that.params); } @Override public int hashCode() { if (params == null) { return Objects.hash(beanName, methodName); } return Objects.hash(beanName, methodName, params); } }
添加定时任务注册类，用来增加、删除定时任务：
@Component public class CronTaskRegistrar implements DisposableBean { private final Map<Runnable, ScheduledTask> scheduledTasks = new ConcurrentHashMap<>(16); @Autowired private TaskScheduler taskScheduler; public TaskScheduler getScheduler() { return this.taskScheduler; } public void addCronTask(Runnable task, String cronExpression) { addCronTask(new CronTask(task, cronExpression)); } public void addCronTask(CronTask cronTask) { if (cronTask != null) { Runnable task = cronTask.getRunnable(); if (this.scheduledTasks.containsKey(task)) { removeCronTask(task); } this.scheduledTasks.put(task, scheduleCronTask(cronTask)); } } public void removeCronTask(Runnable task) { ScheduledTask scheduledTask = this.scheduledTasks.remove(task); if (scheduledTask != null) scheduledTask.cancel(); } public ScheduledTask scheduleCronTask(CronTask cronTask) { ScheduledTask scheduledTask = new ScheduledTask(); scheduledTask.future = this.taskScheduler.schedule(cronTask.getRunnable(), cronTask.getTrigger()); return scheduledTask; } @Override public void destroy() { for (ScheduledTask task : this.scheduledTasks.values()) { task.cancel(); } this.scheduledTasks.clear(); } }
添加定时任务示例类：
@Component("demoTask") public class DemoTask { public void taskWithParams(String params) { System.out.println("执行有参示例任务：" + params); } public void taskNoParams() { System.out.println("执行无参示例任务"); } }
定时任务数据库表设计：
添加定时任务实体类：
public class SysJobPO { /** * 任务ID */ private Integer jobId; /** * bean名称 */ private String beanName; /** * 方法名称 */ private String methodName; /** * 方法参数 */ private String methodParams; /** * cron表达式 */ private String cronExpression; /** * 状态（1正常 0暂停） */ private Integer jobStatus; /** * 备注 */ private String remark; /** * 创建时间 */ private Date createTime; /** * 更新时间 */ private Date updateTime; public Integer getJobId() { return jobId; } public void setJobId(Integer jobId) { this.jobId = jobId; } public String getBeanName() { return beanName; } public void setBeanName(String beanName) { this.beanName = beanName; } public String getMethodName() { return methodName; } public void setMethodName(String methodName) { this.methodName = methodName; } public String getMethodParams() { return methodParams; } public void setMethodParams(String methodParams) { this.methodParams = methodParams; } public String getCronExpression() { return cronExpression; } public void setCronExpression(String cronExpression) { this.cronExpression = cronExpression; } public Integer getJobStatus() { return jobStatus; } public void setJobStatus(Integer jobStatus) { this.jobStatus = jobStatus; } public String getRemark() { return remark; } public void setRemark(String remark) { this.remark = remark; } public Date getCreateTime() { return createTime; } public void setCreateTime(Date createTime) { this.createTime = createTime; } public Date getUpdateTime() { return updateTime; } public void setUpdateTime(Date updateTime) { this.updateTime = updateTime; } }
新增定时任务：
boolean success = sysJobRepository.addSysJob(sysJob); if (!success) return OperationResUtils.fail("新增失败"); else { if (sysJob.getJobStatus().equals(SysJobStatus.NORMAL.ordinal())) { SchedulingRunnable task = new SchedulingRunnable(sysJob.getBeanName(), sysJob.getMethodName(), sysJob.getMethodParams()); cronTaskRegistrar.addCronTask(task, sysJob.getCronExpression()); } } return OperationResUtils.success();
修改定时任务，先移除原来的任务，再启动新任务
boolean success = sysJobRepository.editSysJob(sysJob); if (!success) return OperationResUtils.fail("编辑失败"); else { //先移除再添加 if (existedSysJob.getJobStatus().equals(SysJobStatus.NORMAL.ordinal())) { SchedulingRunnable task = new SchedulingRunnable(existedSysJob.getBeanName(), existedSysJob.getMethodName(), existedSysJob.getMethodParams()); cronTaskRegistrar.removeCronTask(task); } if (sysJob.getJobStatus().equals(SysJobStatus.NORMAL.ordinal())) { SchedulingRunnable task = new SchedulingRunnable(sysJob.getBeanName(), sysJob.getMethodName(), sysJob.getMethodParams()); cronTaskRegistrar.addCronTask(task, sysJob.getCronExpression()); } } return OperationResUtils.success();
删除定时任务
boolean success = sysJobRepository.deleteSysJobById(req.getJobId()); if (!success) return OperationResUtils.fail("删除失败"); else{ if (existedSysJob.getJobStatus().equals(SysJobStatus.NORMAL.ordinal())) { SchedulingRunnable task = new SchedulingRunnable(existedSysJob.getBeanName(), existedSysJob.getMethodName(), existedSysJob.getMethodParams()); cronTaskRegistrar.removeCronTask(task); } } return OperationResUtils.success();
添加实现了CommandLineRunner接口的SysJobRunner类，当spring boot项目启动完成后，加载数据库里状态为正常的定时任务。
@Service public class SysJobRunner implements CommandLineRunner { private static final Logger logger = LoggerFactory.getLogger(SysJobRunner.class); @Autowired private ISysJobRepository sysJobRepository; @Autowired private CronTaskRegistrar cronTaskRegistrar; @Override public void run(String... args) { // 初始加载数据库里状态为正常的定时任务 List<SysJobPO> jobList = sysJobRepository.getSysJobListByStatus(SysJobStatus.NORMAL.ordinal()); if (CollectionUtils.isNotEmpty(jobList)) { for (SysJobPO job : jobList) { SchedulingRunnable task = new SchedulingRunnable(job.getBeanName(), job.getMethodName(), job.getMethodParams()); cronTaskRegistrar.addCronTask(task, job.getCronExpression()); } logger.info("定时任务已加载完毕..."); } } }
工具类SpringContextUtils，用来从spring容器里获取bean
@Component public class SpringContextUtils implements ApplicationContextAware { private static ApplicationContext applicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { SpringContextUtils.applicationContext = applicationContext; } public static Object getBean(String name) { return applicationContext.getBean(name); } public static <T> T getBean(Class<T> requiredType) { return applicationContext.getBean(requiredType); } public static <T> T getBean(String name, Class<T> requiredType) { return applicationContext.getBean(name, requiredType); } public static boolean containsBean(String name) { return applicationContext.containsBean(name); } public static boolean isSingleton(String name) { return applicationContext.isSingleton(name); } public static Class<? extends Object> getType(String name) { return applicationContext.getType(name); } }
好了，今天的学习就到这里！如果您学习过程中如遇困难？可以加入我们超高质量的Spring技术交流群，参与交流与讨论，更好的学习与进步！更多Spring Boot教程可以点击直达！，欢迎收藏与转发支持！
