How to interrupt or stop currently running quartz job?

You need to write a your job as an implementation of InterruptableJob. To interrupt this job, you need handle to Scheduler , and call interrupt(jobKey<<job name & job group>>)

Please have a look @ javadoc for above classes, also quartz distribution contains an example for this (example7).

In Quartz 2.1 with Spring you can:

@Autowired
private Scheduler schedulerFactoryBean; //injected by spring
...
...

List<JobExecutionContext> currentlyExecuting = schedulerFactoryBean.getCurrentlyExecutingJobs();

//verifying if job is running       
for (JobExecutionContext jobExecutionContext : currentlyExecuting) {
    if(jobExecutionContext.getJobDetail().getKey().getName().equals("JobKeyNameToInterrupt")){
        result = schedulerFactoryBean.interrupt(jobExecutionContext.getJobDetail().getKey());
    }
}

The best solution in my opinion is the one described in this thread: http://forums.terracotta.org/forums/posts/list/7700.page

I've just introduced a "sleep" after set stop flag to true to allow the job to finish cleanly.

    @Override
public void interrupt() throws UnableToInterruptJobException {
    stopFlag.set(true);
    try {
        Thread.sleep(30000);
    } catch (InterruptedException e) {
        //logger.error("interrupt()", e);
    }
    Thread thread = runningThread.getAndSet(null);
    if (thread != null)
        thread.interrupt();
}