Exploring Scheduler interface

A scheduler maintains job details and trigger details. Scheduler is responsible to fire the job, when their scheduled time arrives.

How to create a scheduler?

‘SchedulerFactory´interface is used to create a scheduler. Once scheduler is created, it is in stand-by mode. You need to call the start() method explicitly to activate the scheduler.

How to register a job to the scheduler?

Use the scheduleJob method to register a job to the scheduler.

Example

// Initiate a Schedule Factory

SchedulerFactory schedulerFactory = new StdSchedulerFactory();

// Retrieve a scheduler from schedule factory

Scheduler scheduler = schedulerFactory.getScheduler();

// Start scheduler

scheduler.start();

How to identify a job and triggers in a scheduler?

Every job, trigger has a name and group associated with them. These are used to uniquely identify them within a single scheduler.

HelloJob.java

package com.sample.jobs;

import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;

public class HelloJob implements Job {
 public void execute(JobExecutionContext jec) throws JobExecutionException {
  System.out.println("Hello!!!");
 }
}

QuartzSchedulerEx.java

package com.sample.app;

import java.util.Date;

import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.SchedulerFactory;
import org.quartz.impl.JobDetailImpl;
import org.quartz.impl.StdSchedulerFactory;
import org.quartz.impl.triggers.SimpleTriggerImpl;

import com.sample.jobs.HelloJob;

public class QuartzSchedulerEx {
 public static void main(String args[]) throws SchedulerException, InterruptedException {

  // Initiate a Schedule Factory
  SchedulerFactory schedulerFactory = new StdSchedulerFactory();

  // Retrieve a scheduler from schedule factory
  Scheduler scheduler = schedulerFactory.getScheduler();

  // Start scheduler
  scheduler.start();

  JobDetailImpl helloJobDetails = new JobDetailImpl();
  helloJobDetails.setName("Hello Job");
  helloJobDetails.setJobClass(HelloJob.class);

  // Creating schedule time with trigger
  SimpleTriggerImpl trigger1 = new SimpleTriggerImpl();
  trigger1.setStartTime(new Date(System.currentTimeMillis() + 500));
  trigger1.setRepeatCount(-1);
  trigger1.setRepeatInterval(1000);
  trigger1.setName("First Trigger");
  trigger1.setPriority(10); // Setting trigger 1 priority to 10

  scheduler.scheduleJob(helloJobDetails, trigger1);
 }
}

Output

Hello!!!

Hello!!!

Hello!!!

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