【org.quartz.core相关类图】
可以看到核心类为QuartzScheduler
【QuartzScheduler构造函数】
public QuartzScheduler(QuartzSchedulerResources resources, long idleWaitTime, @Deprecated long dbRetryInterval)
throws SchedulerException {
this.resources = resources;
if (resources.getJobStore() instanceof JobListener) {
addInternalJobListener((JobListener)resources.getJobStore());
} this.schedThread = new QuartzSchedulerThread(this, resources);
ThreadExecutor schedThreadExecutor = resources.getThreadExecutor();
schedThreadExecutor.execute(this.schedThread);
if (idleWaitTime > 0) {
this.schedThread.setIdleWaitTime(idleWaitTime);
} jobMgr = new ExecutingJobsManager();
addInternalJobListener(jobMgr);
errLogger = new ErrorLogger();
addInternalSchedulerListener(errLogger); signaler = new SchedulerSignalerImpl(this, this.schedThread); if(shouldRunUpdateCheck())
updateTimer = scheduleUpdateCheck();
else
updateTimer = null; getLog().info("Quartz Scheduler v." + getVersion() + " created.");
}
这里创建了一个QuartzSchedulerThread并在ThreadExecutor（默认DefaultThreadExecutor ）中运行。这里的ThreadExecutor并非我们关心的，继续看QuartzSchedulerThread的run方法。
【QuartzSchedulerThread#run()】
run方法比较长，大意就是根据Trigger找出要运行的job然后在线程池中执行。下面是run方法的代码片段：
JobRunShell shell = null;
try {
shell = qsRsrcs.getJobRunShellFactory().createJobRunShell(bndle);
shell.initialize(qs);
} catch (SchedulerException se) {
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
continue;
} if (qsRsrcs.getThreadPool().runInThread(shell) == false) {
// this case should never happen, as it is indicative of the
// scheduler being shutdown or a bug in the thread pool or
// a thread pool being used concurrently - which the docs
// say not to do...
getLog().error("ThreadPool.runInThread() return false!");
qsRsrcs.getJobStore().triggeredJobComplete(triggers.get(i), bndle.getJobDetail(), CompletedExecutionInstruction.SET_ALL_JOB_TRIGGERS_ERROR);
}
这里的ThreadPool必须实现org.quartz.spi.ThreadPool接口。
【ThreadPool实现类】
ThreadPool的默认实现类是org.quartz.simpl.SimpleThreadPool。
String tpClass = cfg.getStringProperty(PROP_THREAD_POOL_CLASS, SimpleThreadPool.class.getName());
（from org.quartz.impl.StdSchedulerFactory#instantiate()）
这个线程池非常简单，都没有BlockingQueue：
private LinkedList<WorkerThread> availWorkers = new LinkedList<WorkerThread>(); // SimpleThreadPool成员
private LinkedList<WorkerThread> busyWorkers = new LinkedList<WorkerThread>(); // SimpleThreadPool成员
如果与Spring集成，使用org.springframework.scheduling.quartz.SchedulerFactoryBean且配置了taskExecutor（java.util.concurrent.Executor的实现类），则会使用org.springframework.scheduling.quartz.LocalTaskExecutorThreadPool。
if (this.taskExecutor != null) {
mergedProps.setProperty(StdSchedulerFactory.PROP_THREAD_POOL_CLASS,
LocalTaskExecutorThreadPool.class.getName());
}
（from org.springframework.scheduling.quartz.SchedulerFactoryBean#initSchedulerFactory）
也可以自定义实现类，并为quartzProperties配置org.quartz.threadPool.class参数。