利用Spring的ThreadPoolTaskScheduler实现轻量级任务调度

　　在JAVA单体应用中需要一个使用简单性能可靠的调度功能，要求可以通过Cron表达式配置触发时间并且任务执行时间可以修改并且立即生效，可以在运行时动态增加、停止、重启job等。
　　经过研究 org.springframework.scheduling.annotation.SchedulingConfigurer  满足通过Cron表达式配置触发时间、任务执行时间可以修改但不满足修改cron表达式后立即生效，也不支持运行时动态增加、停止、重启job。
　　进一步研究发现可以使用 org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler  满足全部需要。示例代码如下：
　　初始化 ThreadPoolTaskScheduler  :  @Configuration  public class AppConfig {      @Bean      @ConditionalOnBean      public ThreadPoolTaskScheduler getThreadPoolTaskScheduler(){          ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();          taskScheduler.setPoolSize(10);          taskScheduler.setThreadNamePrefix(＂job-schedule-＂);          //   *Set whether to wait for scheduled tasks to complete on shutdown,          //    not interrupting running tasks and executing all tasks in the queue.          taskScheduler.setWaitForTasksToCompleteOnShutdown(true);          /**           *  Set the maximum number of seconds that this executor is supposed to block           *  on shutdown in order to wait for remaining tasks to complete their execution           *  before the rest of the container continues to shut down. This is particularly           *  useful if your remaining tasks are likely to need access to other resources           *  that are also managed by the container.           */          taskScheduler.setAwaitTerminationSeconds(60);          return taskScheduler;      }  }
　　业务对象 SysJobSchedule  :  public class SysJobSchedule {      private String name;      private String code;      private String comment;      private String cron;      private String className;      private Boolean deleteFlag = false;      private Boolean stopFlag = false;      .....   }
　　核心 SmartScheduleJob   @Service  @Slf4j  @EnableScheduling  public class SmartScheduleJob {      private ConcurrentHashMap futureConcurrentHashMap = new ConcurrentHashMap<>();      @Autowired      private ThreadPoolTaskScheduler threadPoolTaskScheduler;              /**       * 启动调度       * @param jobSchedule       */      public void startSchedule(SysJobSchedule jobSchedule) {          if (jobSchedule != null) {              log.info(＂启动Job {}＂,jobSchedule.getClassName());              stopSchedule(jobSchedule.getClassName());              initSchedule(jobSchedule);          }      }        /**       * 关闭调度       * @param className       */      public void stopSchedule((SysJobSchedule jobSchedule) {          String className = jobSchedule.getgClassName();          ScheduledFuture scheduledFuture = this.futureConcurrentHashMap.get(className);          if (scheduledFuture != null) {              log.info(＂==关闭Job：{}＂, className);              futureConcurrentHashMap.remove(className);              if (!scheduledFuture.isCancelled())                  scheduledFuture.cancel(true);          }      }          private void initSchedule(SysJobSchedule jobSchedule) {          if(jobSchedule.getStopFlag())              return;          ScheduledFuture future = this.threadPoolTaskScheduler.schedule(                  //1.添加任务内容(Runnable)                  () -> {                      this.doTask(jobSchedule);                  },                  //2.设置执行周期(Trigger)                  triggerContext -> {                                                    String cron = jobSchedule.getCron();                                       return new CronTrigger(cron).nextExecutionTime(triggerContext);                  }          );          //将ScheduledFuture添加到ConcurrentHashMap中          futureConcurrentHashMap.put(jobSchedule.getClassName(), future);      }        private void doTask(SysJobSchedule jobSchedule) {        doSomething…      }    }
　　ThreadPoolTaskScheduler  为轻量级任务调度器适用于单体应用，不适合分布式集群部署，由于节点之间没有共享信息，因而会出现多次调度的情况.