Spring调度程序如何动态更改cron表达式

Question

我可以在applicationContext.xml中创建一个taskScheduler，根据属性定期触发我的作业。

我想在调度程序启动后更改这个表达式（触发周期），也就是说，在JavaEE应用程序运行时更改它。

使用Spring 3.XX

- Ahmet Karakaya

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请展示您的 taskScheduler bean 定义。 - Sotirios Delimanolis

无法提供URL的翻译。请提供需要翻译的文本。 - Praba

Answer 1

实际上，我面临了同样的问题。

我假设您需要从用户那里获取日期（1-31）、时间、星期几和调度程序类型（每日、每月、每周）。

首先，您需要从用户给出的日期时间创建cron表达式。以下代码将创建cron表达式，它接受一个映射并返回cron表达式字符串。

public String  getCronExp(final Map<String, Object> configMap) {

    LOGGER.debug(">>  getCronExp");

    String exp = "";

    final String type = (String) configMap.get(SCHEDULER_TYPE);
    final String time = (String) configMap.get(TIME);
    final String[] split = time.split(this.COLON);
    String hour = split[0];
    String min = split[1];

    if ("00".equalsIgnoreCase(min)) {
        min = ZERO;
    }
    if ("00".equalsIgnoreCase(hour)) {
        hour = "0";
    }
    if ("daily".equalsIgnoreCase(type)) {

        exp = this.ZERO + this.WHITE_SPACE + min + this.WHITE_SPACE + hour + this.WHITE_SPACE + this.ASTERISK + this.WHITE_SPACE + this.ASTERISK
                + this.WHITE_SPACE + "?";

    } else if ("monthly".equalsIgnoreCase(type)) {
        final String date = (String) configMap.get(START_DATE);
        exp = this.ZERO + this.WHITE_SPACE + min + this.WHITE_SPACE + hour + this.WHITE_SPACE + date + this.WHITE_SPACE + this.ASTERISK + this.WHITE_SPACE
                + "?";

    } else if ("weekly".equalsIgnoreCase(type)) {

        final String dayOfWeek = (String) configMap.get(DAY_OF_WEEK);

        exp = this.ZERO + this.WHITE_SPACE + min + this.WHITE_SPACE + hour + this.WHITE_SPACE + "?" + this.WHITE_SPACE + this.ASTERISK + this.WHITE_SPACE
                + dayOfWeek;
    }

    LOGGER.info("Latest cron  expression scheduler " + exp);
    LOGGER.debug("<<  getCronExp");
    return exp;
}

得到cron表达式后，我们需要解决触发调度器的问题。

创建一个继承Runnable的类：

public  class Scheduler implements Runnable {

@SuppressWarnings("rawtypes")
ScheduledFuture scheduledFuture;

TaskScheduler taskScheduler ;

//this method will kill previous scheduler if exists and will create a new scheduler with given cron expression
public  void reSchedule(String cronExpressionStr){
 if(taskScheduler== null){
        this.taskScheduler = new ConcurrentTaskScheduler();
    }
     if (this.scheduledFuture() != null) {
        this.scheduledFuture().cancel(true);
    }
 this.scheduledFuture = this.taskScheduler.schedule(this, new CronTrigger(cronExpressionStr));
}

@Override
public  void run(){
// task to be performed 
}

//if you want on application to read data on startup from db and schedule the schduler use following method
 @PostConstruct
  public void initializeScheduler() {
    //@postcontruct method will be called after creating all beans in application context
    // read user config map from db 
    // get cron expression created 
    this.reSchedule(cronExp);
  }

}

- Prafful Nagpal