Java job scheduler- Quartz Scheduler

We know about cron job in unix. If we want to schedule any job in a particular day and time ,use corn scheduler in unix.

Being a java developer we always think if we can do the same  in java. If we want to schedule a job in java we can use “Quartz Scheduler”. java job scheduler is easy to configure.

To trigger a job we should use “cron expressions”, it tells when a job should be trigger. Below are the few examples of “cron expressions”

 

**Expression**	**Meaning**
0 0 12 * * ?	Fire at 12pm (noon) every day
0 15 10 ? * *	Fire at 10:15am every day
0 15 10 * * ?	Fire at 10:15am every day
0 15 10 * * ? *	Fire at 10:15am every day
0 15 10 * * ? 2005	Fire at 10:15am every day during the year 2005
0 * 14 * * ?	Fire every minute starting at 2pm and ending at 2:59pm, every day
0 0/5 14 * * ?	Fire every 5 minutes starting at 2pm and ending at 2:55pm, every day
0 0/5 14,18 * * ?	Fire every 5 minutes starting at 2pm and ending at 2:55pm, AND fire every 5 minutes starting at 6pm and ending at 6:55pm, every day
0 0-5 14 * * ?	Fire every minute starting at 2pm and ending at 2:05pm, every day
0 10,44 14 ? 3 WED	Fire at 2:10pm and at 2:44pm every Wednesday in the month of March.
0 15 10 ? * MON-FRI	Fire at 10:15am every Monday, Tuesday, Wednesday, Thursday and Friday
0 15 10 15 * ?	Fire at 10:15am on the 15th day of every month
0 15 10 L * ?	Fire at 10:15am on the last day of every month
0 15 10 L-2 * ?	Fire at 10:15am on the 2nd-to-last last day of every month
0 15 10 ? * 6L	Fire at 10:15am on the last Friday of every month
0 15 10 ? * 6L	Fire at 10:15am on the last Friday of every month
0 15 10 ? * 6L 2002-2005	Fire at 10:15am on every last friday of every month during the years 2002, 2003, 2004 and 2005
0 15 10 ? * 6#3	Fire at 10:15am on the third Friday of every month
0 0 12 1/5 * ?	Fire at 12pm (noon) every 5 days every month, starting on the first day of the month.
0 11 11 11 11 ?	Fire every November 11th at 11:11am.

For more detail please check http://quartz-scheduler.org/documentation/quartz-2.1.x/tutorials/crontrigger

 

Project structure

 

Please follow the below steps to schedule a job in java based project.

1. CronScheduler.java

package com.codewale.example;
import java.util.Map;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import org.quartz.CronScheduleBuilder;
import org.quartz.JobBuilder;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.Trigger;
import org.quartz.TriggerBuilder;
import org.quartz.impl.StdSchedulerFactory;
public class CronScheduler extends HttpServlet{
public void scheduleJob1() {
String jobname = "This is job1";
String triggername = "Trigger 1";
String scheduletime = "0 0/2 * * * ?";
if(jobname!=null)
{
System.out.println("JOBNAME1="+jobname+" TRIGGERNAME1="+triggername+" JOBCRONEXPR1="+scheduletime);
JobDetail job;
job = JobBuilder.newJob(Job1.class).withIdentity(jobname).build();
Trigger trigger = TriggerBuilder.newTrigger().withIdentity(triggername).withSchedule(CronScheduleBuilder.cronSchedule(scheduletime)).build();
Scheduler scheduler=null;
try {
scheduler = new StdSchedulerFactory().getScheduler();
scheduler.start();
scheduler.scheduleJob(job, trigger);
} catch(SchedulerException e){
try {
scheduler.shutdown(true);
} catch (SchedulerException f) {
f.printStackTrace();
}
}
}
}
public void scheduleJob2() {
String jobname = "This is job2";
String triggername = "Trigger 2";
String scheduletime = "0 0/2 * * * ?";
if(jobname!=null)
{
System.out.println("JOBNAME2="+jobname+" TRIGGERNAME2="+triggername+" JOBCRONEXPR2="+scheduletime);
JobDetail job;
job = JobBuilder.newJob(Job2.class).withIdentity(jobname).build();
Trigger trigger = TriggerBuilder.newTrigger().withIdentity(triggername).withSchedule(CronScheduleBuilder.cronSchedule(scheduletime)).build();
Scheduler scheduler=null;
try {
scheduler = new StdSchedulerFactory().getScheduler();
scheduler.start();
scheduler.scheduleJob(job, trigger);
} catch(SchedulerException e){
try {
scheduler.shutdown(true);
} catch (SchedulerException f) {
f.printStackTrace();
}
}
}
}
public void init(ServletConfig config) throws ServletException
{
super.init(config);
System.out.println(" Initializing scheduled tasks from Job1.............");
scheduleJob1();
System.out.println(" Initializing scheduled tasks from Job2.............");
scheduleJob2();
}
}

2.Job1.java

package com.codewale.example;
import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
public class Job1 implements Job{
@Override
public void execute(JobExecutionContext arg0) throws JobExecutionException {
// TODO Auto-generated method stub
System.out.println("Job1 started ..........................");
}
}

3.Job2.java

package com.codewale.example;
import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
public class Job2 implements Job{
@Override
public void execute(JobExecutionContext arg0) throws JobExecutionException {
// you can execute you job here

System.out.println("Job2 started ..........................");
}
}

4.Index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1">







Please check the log /console, if jobs started.

5.Web.xml

 CronSchedulerInjava
 
 
  index.html
  index.htm
  index.jsp
  default.html
  default.htm
  default.jsp
 
 
 
 
  CronScheduler
  com.codewale.example.CronScheduler
  5
 

When server will start, web.xml will be loaded, it will load the CronScheduler class. CronScheduler will decide which job it will execute.

Don’t forget to  configure the web.xml 
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