Quartz初體驗 - Job and Job Details

參考下列片段：

 
// define the job and tie it to our HelloJob class
  JobDetail job = newJob(HelloJob.class)
      .withIdentity("myJob", "group1") // name "myJob", group "group1"
      .build();
        
  // Trigger the job to run now, and then every 40 seconds
  Trigger trigger = newTrigger()
      .withIdentity("myTrigger", "group1")
      .startNow()
      .withSchedule(simpleSchedule()
          .withIntervalInSeconds(40)
          .repeatForever())            
      .build();
        
  // Tell quartz to schedule the job using our trigger
  sched.scheduleJob(job, trigger);

line 1~3說明了最簡單建立Job的方式，提供簡單的extend Job的Class！Job的建立生命週期如下：

1. Shedule建立執行Job之前(call job's execute(..))，便為Job建立新的instance(如上述的HelloJob)
2. Shedule call job's execute(..)
3. job使用完畢，等待被GC回收

因此由上述可見，我們並無法使用任何有狀態、或需要保存資料的Job，或於Job執行前給予特定資料，因為Job永遠是使用default constuctor建立且於每次execute時重新建立、之後回收。

那麼，我們要怎麼樣在Job被execute之前指定特定資料呢？

使用JobDataMap

1.設定資料：

   
// define the job and tie it to our DumbJob class
  JobDetail job = newJob(DumbJob.class)
      .withIdentity("myJob", "group1") // name "myJob", group "group1"
      .usingJobData("jobSays", "Hello World!")
      .usingJobData("myFloatValue", 3.141f)
      .build();

2.取得資料：

 
public class DumbJob implements Job {

    public DumbJob() {
    }

    public void execute(JobExecutionContext context)
      throws JobExecutionException
    {
      JobKey key = context.getJobDetail().getKey();

      JobDataMap dataMap = context.getJobDetail().getJobDataMap();

      String jobSays = dataMap.getString("jobSays");
      float myFloatValue = dataMap.getFloat("myFloatValue");

      System.err.println("Instance " + key + " of DumbJob says: " + jobSays + ", and val is: " + myFloatValue);
    }
  }

如上述範例，可先於創立JobDetail時指定資料，後於Job execute()時使用getJobDetail().getJobDataMap();取得所需資料。
然而需注意的是，置放於DataMap()的資料皆需為serialized 

參考：Lesson 3: More About Jobs and Job Details