Quartz是一款定时任务调度的开源框架，使用起来比较方便。并且Spring的support包对Quartz有集成。但是笔者在web应用使用的过程中却遇到了内存泄漏的问题。
问题的产生
笔者在使用Spring+Quartz的用法如下（熟悉Spring+Quartz的可以跳过直接看问题）：
1.配置Scheduler工厂
<bean>
</bean>
2.编写Job的实现类QuartzJob，用来执行任务
//这里须继承spring的QuartzJobBean
public class QuartzJob extends QuartzJobBean {/**
* 任务执行内容。
*/
@Override
protected void executeInternal(JobExecutionContext context) throws JobExecutionException {
// 执行任务的代码
}
}
3.将Scheduler工厂生产的scheduler注入到业务逻辑类中。这里注意，注入的其实是由schedulerFactory生产出来的scheduler实例（对Spring不熟悉的人会自然而然的认为注入的是schedulerFactory的实例，这是因为Spring的SchedulerFactoryBean实现了FactoryBean接口，所以注入的结果会是FactoryBean.getObject()获得的实例，题外话）。
<bean init-method="init" scope="singleton">
<property>
<ref bean="schedulerFactory"/>
</property>
</bean>
public class TaskServiceImpl {
private Scheduler scheduler;/**
* 由spring通过工厂注入，此实例为单例。
* @param scheduler
*/
public void setScheduler(Scheduler scheduler) {
this.scheduler = scheduler;
}
4.在业务逻辑类TaskServiceImpl中，使用scheduler执行任务。这里可以动态对任务执行增加、删除、重启等等操作。还有一个重要的特性是可以动态的改变Cron表达式，对任务的定时规则进行更改。
1 /**
2 * 新增任务。
3 * @param jobName
4 * @param jobGroup
5 * @param cron
6 */
7 public void addJob(String jobName, String jobGroup, String cron, String kindId) {
8 try {
9 if (StringUtil.isEmpty(jobName) || StringUtil.isEmpty(jobGroup) || StringUtil.isEmpty(cron)) {
10 throw new BusinessException("定时任务创建失败，参数为空");
11 }
12 JobDetail jobDetail = JobBuilder.newJob(QuartzJob.class).withIdentity(jobName, jobGroup).build();
13 jobDetail.getJobDataMap().put("JobKind", kindId);
14 //表达式调度构建器
15 CronScheduleBuilder scheduleBuilder = CronScheduleBuilder.cronSchedule(cron);
16 //按新的cronExpression表达式构建一个新的trigger
17 CronTrigger trigger = TriggerBuilder.newTrigger().withIdentity(jobName, jobGroup).withSchedule(scheduleBuilder).build();
18 scheduler.scheduleJob(jobDetail, trigger);
19 log.info("新增定时任务，name:" + jobName + ",group:" + jobGroup + ",cron:" + cron);
20 } catch (SchedulerException e) {
21 // 对异常的处理
22 }
23 }
注意18行的scheduler是由Spring注入的。
这种用法在使用过程中没有问题，但在web应用在Tomcat6中热部署时出险了以下严重警告，如果忽略这种警告，在频繁的reload后会造成Tomcat 的 Permgen space OOM。
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-1] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-2] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-3] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-4] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-5] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/feeder##1.5.0] appears to have started a thread named [scheduler_Worker-6] but has failed to stop it. This is very likely to create a memory leak.
Jun 24, 2014 5:14:38 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
问题的原因
究其原因是开启的scheduler_Worker线程没有关闭。但Spring的SchedulerFactoryBean实现了DisposableBean接口，表示web容器关闭时会执行destroy()，执行内容如下：