Example 4 - Job Parameters and Job State

This example is designed to demonstrate how you can pass run-time parameters into quartz jobs and how you can maintain state in a job.

The program will perform the following actions:

• Start up the Quartz Scheduler
• Schedule two jobs, each job will execute the every ten seconds for a total of times
• The scheduler will pass a run-time job parameter of “Green” to the first job instance
• The scheduler will pass a run-time job parameter of “Red” to the second job instance
• The program will wait 60 seconds so that the two jobs have plenty of time to run
• Shut down the Scheduler

Running the Example

This example can be executed from the examples/example4 directory. There are two out-of-the-box methods for running this example

• example4.sh - A UNIX/Linux shell script
• example4.bat - A Windows Batch file

The Code

The code for this example resides in the package org.quartz.examples.example4.

The code in this example is made up of the following classes:

ColorJob

ColorJob is a simple class that implement the Job interface, and is annotated as such:

@PersistJobDataAfterExecution
@DisallowConcurrentExecution
public class ColorJob implements Job {

The annotations cause behavior just as their names describe - multiple instances of the job will not be allowed to run concurrently (consider a case where a job has code in its execute() method that takes 34 seconds to run, but it is scheduled with a trigger that repeats every 30 seconds), and will have its JobDataMap contents re-persisted in the scheduler’s JobStore after each execution. For the purposes of this example, only @PersistJobDataAfterExecution annotation is truly relevant, but it’s always wise to use the @DisallowConcurrentExecution annotation with it, to prevent race-conditions on saved data.

ColorJob logs the following information when the job is executed:

• The job’s identification key (name and group) and time/date of execution
• The job’s favorite color (which is passed in as a run-time parameter)
• The job’s execution count calculated from a member variable
• The job’s execution count maintained as a job map parameter

_log.info("ColorJob: " + jobKey + " executing at " + new Date() + "\n" +
    "  favorite color is " + favoriteColor + "\n" +
    "  execution count (from job map) is " + count + "\n" +
    "  execution count (from job member variable) is " + _counter);

The variable favoriteColor is passed in as a job parameter. It is retrieved as follows from the JobDataMap:

JobDataMap data = context.getJobDetail().getJobDataMap();
String favoriteColor = data.getString(FAVORITE_COLOR);

The variable count is stored in the job data map as well:

JobDataMap data = context.getJobDetail().getJobDataMap();
int count = data.getInt(EXECUTION_COUNT);

The variable is later incremented and stored back into the job data map so that job state can be preserved:

count++;
data.put(EXECUTION_COUNT, count);

There is also a member variable named counter. This variable is defined as a member variable to the class:

private int _counter = 1;

This variable is also incremented and displayed. However, its count will always be displayed as “1” because Quartz will always instantiate a new instance of the class during each execution - which prevents member variables from being used to maintain state.

JobStateExample

The program starts by getting an instance of the Scheduler. This is done by creating a StdSchedulerFactory and then using it to create a scheduler. This will create a simple, RAM-based scheduler.

SchedulerFactory sf = new StdSchedulerFactory();
Scheduler sched = sf.getScheduler();

Job #1 is scheduled to run every 10 seconds, for a total of five times:

JobDetail job1 = newJob(ColorJob.class)
    .withIdentity("job1", "group1")
    .build();

SimpleTrigger trigger1 = newTrigger()
    .withIdentity("trigger1", "group1")
    .startAt(startTime)
    .withSchedule(simpleSchedule()
            .withIntervalInSeconds(10)
            .withRepeatCount(4))
    .build();

Job #1 is passed in two job parameters. One is a favorite color, with a value of “Green”. The other is an execution count, which is initialized with a value of 1.

job1.getJobDataMap().put(ColorJob.FAVORITE_COLOR, "Green");
job1.getJobDataMap().put(ColorJob.EXECUTION_COUNT, 1);

Job #2 is also scheduled to run every 10 seconds, for a total of five times:

JobDetail job2 = newJob(ColorJob.class)
    .withIdentity("job2", "group1")
    .build();

SimpleTrigger trigger2 = newTrigger()
    .withIdentity("trigger2", "group1")
    .startAt(startTime)
    .withSchedule(simpleSchedule()
            .withIntervalInSeconds(10)
            .withRepeatCount(4))
    .build();

Job #2 is also passed in two job parameters. One is a favorite color, with a value of “Red”. The other is an execution count, which is initialized with a value of 1.

job2.getJobDataMap().put(ColorJob.FAVORITE_COLOR, "Red");
job2.getJobDataMap().put(ColorJob.EXECUTION_COUNT, 1);

The scheduler is then started.

sched.start();

To let the program have an opportunity to run the job, we then sleep for one minute (60 seconds)

Thread.sleep(60L * 1000L);

Finally, we will gracefully shutdown the scheduler:

sched.shutdown(true);

Note: passing true into the shutdown message tells the Quartz Scheduler to wait until all jobs have completed running before returning from the method call.