上一篇分析了elastic-job与quartz怎么结合，启动作业。那么作业是怎么执行的呢？我猜想是quartz启动作业后，会起个线程，根据cron表达式的规则去执行作业，翻了一下源码验证一下，quartz使用JobRunShell运行作业：

public void run() {
    ```省略```
    OperableTrigger trigger = (OperableTrigger) jec.getTrigger();
    JobDetail jobDetail = jec.getJobDetail();
    ```省略```
    job.execute(jec);// execute the job
    ````省略```
}

上面的代码，执行实现Job接口的类的execute方法：

public interface Job {
    void execute(JobExecutionContext context) throws JobExecutionException;
}

那么elastic-job实现Job接口实现liteJob,也就是说quartz执行的liteJob这个类：

/**
 * Lite调度作业.
 *
 * @author zhangliang
 */
public final class LiteJob implements Job {

    @Setter
    private ElasticJob elasticJob;

    @Setter
    private JobFacade jobFacade;

    @Override
    public void execute(final JobExecutionContext context) throws JobExecutionException {
        JobExecutorFactory.getJobExecutor(elasticJob, jobFacade).execute();
    }
}

到此为止，就把quartz的JOB执行过程与elastic-job的作业联系到一起了。
那么，litejob的elasticJob，jobFacade二个属性值是什么时候塞进去的呢?
还是找源码，这里比较隐秘，回到quartz中JobRunShell的initialize（）方法：

public void initialize(QuartzScheduler sched)throws SchedulerException {
    this.qs = sched;

    Job job = null;
    JobDetail jobDetail = firedTriggerBundle.getJobDetail();

    try {
        job = sched.getJobFactory().newJob(firedTriggerBundle, scheduler);//初始化JOB
    } catch (SchedulerException se) {
        ···
    }
    this.jec = new JobExecutionContextImpl(scheduler, firedTriggerBundle, job);//初始化JOB的一些上下文参数
}

job = sched.getJobFactory().newJob(firedTriggerBundle, scheduler)这个方法获取jobFactory,这里使用的是PropertySettingJobFactory extend SimpleJobFacotry，再通过反射实例化了实现JOB接口的liteJob，看下是怎么实现的：

public class PropertySettingJobFactory extends SimpleJobFactory {
  ...
    @Override
public Job newJob(TriggerFiredBundle bundle, Scheduler scheduler) throws SchedulerException {

    Job job = super.newJob(bundle, scheduler);//反射实例化Job

    JobDataMap jobDataMap = new JobDataMap();
    jobDataMap.putAll(scheduler.getContext());
    jobDataMap.putAll(bundle.getJobDetail().getJobDataMap());
    jobDataMap.putAll(bundle.getTrigger().getJobDataMap());
    /**
     * 上面的LiteJob.class,其中有两个成员变量,
     * elasticJob和jobFacade就是这里来初始化的。
     * 通过反射
     */
    setBeanProps(job, jobDataMap);

    return job;
}

public class SimpleJobFactory implements JobFactory {
...
/**
 * 根据JobDetail中的JobClass类来生成一个实例。
 */
public Job newJob(TriggerFiredBundle bundle, Scheduler Scheduler) throws SchedulerException {
    JobDetail jobDetail = bundle.getJobDetail();
    Class<? extends Job> jobClass = jobDetail.getJobClass();
    try {
        if(log.isDebugEnabled()) {
            log.debug(
                "Producing instance of Job '" + jobDetail.getKey() + 
                "', class=" + jobClass.getName());
        }

        return jobClass.newInstance();
    } catch (Exception e) {
        SchedulerException se = new SchedulerException(
                "Problem instantiating class '"
                        + jobDetail.getJobClass().getName() + "'", e);
        throw se;
    }
  }
}

liteJob.class是从jobDetail里面get的，上一节中，提到了作业启动过程中，JobScheduler中init（）调用了createJobDetail（）这个方法：

 private JobDetail createJobDetail(final String jobClass) {
    JobDetail result = JobBuilder.newJob(LiteJob.class).withIdentity(liteJobConfig.getJobName()).build();//告诉quartz的JOB类型是liteJob
    result.getJobDataMap().put(JOB_FACADE_DATA_MAP_KEY, jobFacade);//liteJob的属性值jobFacade初始化，put到jobDetail的jobdataMap
    Optional<ElasticJob> elasticJobInstance = createElasticJobInstance();
    if (elasticJobInstance.isPresent()) {
        result.getJobDataMap().put(ELASTIC_JOB_DATA_MAP_KEY, elasticJobInstance.get());//liteJob的属性值elasticJob初始化，put到jobDetail的jobdataMap
    } else if (!jobClass.equals(ScriptJob.class.getCanonicalName())) {
        try {
            result.getJobDataMap().put(ELASTIC_JOB_DATA_MAP_KEY, Class.forName(jobClass).newInstance());
        } catch (final ReflectiveOperationException ex) {
            throw new JobConfigurationException("Elastic-Job: Job class '%s' can not initialize.", jobClass);
        }
    }
    return result;
}

至此，liteJob 什么时候初始化，以及他的属性jobFacade，elasticJob是什么地方set进去的，就清楚了。