大家好，欢迎来到IT知识分享网。
一、前言介绍
在日常开发中经常会用到定时任务，用来；库表扫描发送MQ、T+n账单结算、缓存数据更新、秒杀活动状态变更，等等。因为有了Spring的Schedule极大的方便了我们对这类场景的使用。那么，除了应用你还了解它多少呢；
- 默认初始化多少个任务线程
- JobStore有几种实现，你平时用的都是哪个
- 一个定时任务的执行流程简述下
蒙圈了吧，是不感觉平时只是使用了，根本没关注过这些。有种冲动赶紧搜索答案吧！但只是知道答案是没有多少意义的，扛不住问不说，也不了解原理。所以，如果你想真的提升自己技能，还是要从根本搞定。
二、案例工程
为了更好的做源码分析，我们将平时用的定时任务服务单独抽离出来。工程下载，关注公众号：bugstack虫洞栈，回复：源码分析
itstack-demo-code-schedule
└── src
├── main
│ ├── java
│ │ └── org.itstack.demo
│ │ ├── DemoTask.java
│ │ └── JobImpl.java
│ └── resources
│ ├── props
│ │ └── config.properties
│ ├── spring
│ │ └── spring-config-schedule-task.xml
│ ├── logback.xml
│ └── spring-config.xml
└── test
└── java
└── org.itstack.demo.test
├── ApiTest.java
├── MyQuartz.java
└── MyTask.java
三、环境配置
- JDK 1.8
- IDEA 2019.3.1
- Spring 4.3.24.RELEASE
- quartz 2.3.2 ｛不同版本略有代码差异｝
四、源码分析
<dependency>
<groupId>org.quartz-scheduler</groupId>
<artifactId>quartz</artifactId>
<version>2.3.2</version>
</dependency>依赖于Spring版本升级quartz选择2.3.2，同时如果你如本文案例中所示使用xml配置任务。那么会有如下更改；
Spring 3.x/org.springframework.scheduling.quart.CronTriggerBean
<bean id="taskTrigger" class="org.springframework.scheduling.quartz.CronTriggerBean">
<property name="jobDetail" ref="taskHandler"/>
<property name="cronExpression" value="0/5 * * * * ?"/>
</bean>
Spring 4.x/org.springframework.scheduling.quartz.CronTriggerFactoryBean
<bean id="taskTrigger" class="org.springframework.scheduling.quartz.CronTriggerFactoryBean">
<property name="jobDetail" ref="taskHandler"/>
<property name="cronExpression" value="0/5 * * * * ?"/>
</bean>在正式分析前，可以看下quartz的默认配置，很多初始化动作都要从这里取得参数，同样你可以配置自己的配置文件。例如，当你的任务很多时，默认初始化的10个线程组不满足你的业务需求，就可以按需调整。
quart.properties
# Default Properties file for use by StdSchedulerFactory
# to create a Quartz Scheduler Instance, if a different
# properties file is not explicitly specified.
#
org.quartz.scheduler.instanceName: DefaultQuartzScheduler
org.quartz.scheduler.rmi.export: false
org.quartz.scheduler.rmi.proxy: false
org.quartz.scheduler.wrapJobExecutionInUserTransaction: false
org.quartz.threadPool.class: org.quartz.simpl.SimpleThreadPool
org.quartz.threadPool.threadCount: 10
org.quartz.threadPool.threadPriority: 5
org.quartz.threadPool.threadsInheritContextClassLoaderOfInitializingThread: true
org.quartz.jobStore.misfireThreshold: 60000
org.quartz.jobStore.class: org.quartz.simpl.RAMJobStore
1. 从一个简单案例开始
平时我们使用Schedule基本都是注解或者xml配置文件，但是为了可以更简单的分析代码，我们从一个简单的Demo入手，放到main函数中。
DemoTask.java & 定义一个等待被执行的任务
public class DemoTask {
private Logger logger = LoggerFactory.getLogger(DemoTask.class);
public void execute() throws Exception{
logger.info("定时处理用户信息任务：0/5 * * * * ?");
}
}
MyTask.java & 测试类，将配置在xml中的代码抽离出来
public class MyTask {
public static void main(String[] args) throws Exception {
DemoTask demoTask = new DemoTask();
// 定义了；执行的内容
MethodInvokingJobDetailFactoryBean methodInvokingJobDetailFactoryBean = new MethodInvokingJobDetailFactoryBean();
methodInvokingJobDetailFactoryBean.setTargetObject(demoTask);
methodInvokingJobDetailFactoryBean.setTargetMethod("execute");
methodInvokingJobDetailFactoryBean.setConcurrent(true);
methodInvokingJobDetailFactoryBean.setName("demoTask");
methodInvokingJobDetailFactoryBean.afterPropertiesSet();
// 定义了；执行的计划
CronTriggerFactoryBean cronTriggerFactoryBean = new CronTriggerFactoryBean();
cronTriggerFactoryBean.setJobDetail(methodInvokingJobDetailFactoryBean.getObject());
cronTriggerFactoryBean.setCronExpression("0/5 * * * * ?");
cronTriggerFactoryBean.setName("demoTask");
cronTriggerFactoryBean.afterPropertiesSet();
// 实现了；执行的功能
SchedulerFactoryBean schedulerFactoryBean = new SchedulerFactoryBean();
schedulerFactoryBean.setTriggers(cronTriggerFactoryBean.getObject());
schedulerFactoryBean.setAutoStartup(true);
schedulerFactoryBean.afterPropertiesSet();
schedulerFactoryBean.start();
// 暂停住
System.in.read();
}
}
如果一切顺利，那么会有如下结果：
2021-09-21 10:47:16.369 [main] INFO org.quartz.impl.StdSchedulerFactory[1220] - Using default implementation for ThreadExecutor
2021-09-21 10:47:16.421 [main] INFO org.quartz.core.SchedulerSignalerImpl[61] - Initialized Scheduler Signaller of type: class org.quartz.core.SchedulerSignalerImpl
2021-09-21 10:47:16.422 [main] INFO org.quartz.core.QuartzScheduler[229] - Quartz Scheduler v.2.3.2 created.
2021-09-21 10:47:16.423 [main] INFO org.quartz.simpl.RAMJobStore[155] - RAMJobStore initialized.
2021-09-21 10:47:16.424 [main] INFO org.quartz.core.QuartzScheduler[294] - Scheduler meta-data: Quartz Scheduler (v2.3.2) 'QuartzScheduler' with instanceId 'NON_CLUSTERED'
Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.
NOT STARTED.
Currently in standby mode.
Number of jobs executed: 0
Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 10 threads.
Using job-store 'org.quartz.simpl.RAMJobStore' - which does not support persistence. and is not clustered.
2021-09-21 10:47:16.424 [main] INFO org.quartz.impl.StdSchedulerFactory[1374] - Quartz scheduler 'QuartzScheduler' initialized from an externally provided properties instance.
2021-09-21 10:47:16.424 [main] INFO org.quartz.impl.StdSchedulerFactory[1378] - Quartz scheduler version: 2.3.2
2021-09-21 10:47:16.426 [main] INFO org.quartz.core.QuartzScheduler[2293] - JobFactory set to: org.springframework.scheduling.quartz.AdaptableJobFactory@3e9b1010
2021-09-21 10:47:16.651 [main] INFO org.quartz.core.QuartzScheduler[547] - Scheduler QuartzScheduler_$_NON_CLUSTERED started.
九月 21, 2021 10:47:16 上午 org.springframework.scheduling.quartz.SchedulerFactoryBean startScheduler
信息: Starting Quartz Scheduler now
2021-09-21 10:47:20.321 [QuartzScheduler_Worker-1] INFO org.itstack.demo.DemoTask[11] - 定时处理用户信息任务：0/5 * * * * ?
2021-09-21 10:47:25.001 [QuartzScheduler_Worker-2] INFO org.itstack.demo.DemoTask[11] - 定时处理用户信息任务：0/5 * * * * ?
2021-09-21 10:47:30.000 [QuartzScheduler_Worker-3] INFO org.itstack.demo.DemoTask[11] - 定时处理用户信息任务：0/5 * * * * ?
2021-09-21 10:47:35.001 [QuartzScheduler_Worker-4] INFO org.itstack.demo.DemoTask[11] - 定时处理用户信息任务：0/5 * * * * ?
2021-09-21 10:47:40.000 [QuartzScheduler_Worker-5] INFO org.itstack.demo.DemoTask[11] - 定时处理用户信息任务：0/5 * * * * ?
Process finished with exit code -1
2. 定义执行内容(MethodInvokingJobDetailFactoryBean)
// 定义了；执行的内容
MethodInvokingJobDetailFactoryBean methodInvokingJobDetailFactoryBean = new MethodInvokingJobDetailFactoryBean();
methodInvokingJobDetailFactoryBean.setTargetObject(demoTask);
methodInvokingJobDetailFactoryBean.setTargetMethod("execute");
methodInvokingJobDetailFactoryBean.setConcurrent(true);
methodInvokingJobDetailFactoryBean.setName("demoTask");
methodInvokingJobDetailFactoryBean.afterPropertiesSet();
这块内容主要将我们的任务体(即待执行任务DemoTask)交给MethodInvokingJobDetailFactoryBean管理，首先设置必要信息；
- targetObject：目标对象bean，也就是demoTask
- targetMethod：目标方法name，也就是execute
- concurrent：是否并行执行，非并行执行任务，如果上一个任务没有执行完，下一刻不会执行
- name：xml配置非必传，源码中可以获取beanName
最后我们通过手动调用 afterPropertiesSet() 来模拟初始化。如果我们的类是交给 Spring 管理的，那么在实现了 InitializingBean 接口的类，在类配置信息加载后会自动执行 afterPropertiesSet() 。一般实现了 InitializingBean 接口的类，同时也会去实现 FactoryBean 接口，因为这个接口实现后就可以通过 T getObject() 获取自己自定义初始化的类。这也常常用在一些框架开发中。
MethodInvokingJobDetailFactoryBean.afterPropertiesSet()
public void afterPropertiesSet() throws ClassNotFoundException, NoSuchMethodException {
prepare();
// Use specific name if given, else fall back to bean name.
String name = (this.name != null ? this.name : this.beanName);
// Consider the concurrent flag to choose between stateful and stateless job.
Class<?> jobClass = (this.concurrent ? MethodInvokingJob.class : StatefulMethodInvokingJob.class);
// Build JobDetail instance.
JobDetailImpl jdi = new JobDetailImpl();
jdi.setName(name);
jdi.setGroup(this.group);
jdi.setJobClass((Class) jobClass);
jdi.setDurability(true);
jdi.getJobDataMap().put("methodInvoker", this);
this.jobDetail = jdi;
postProcessJobDetail(this.jobDetail);
}
- 源码168行： 根据是否并行执行选择任务类，这两个类都是MethodInvokingJobDetailFactoryBean的内部类，非并行执行的StatefulMethodInvokingJob只是继承MethodInvokingJob添加了标记注解。
- 源码171行： 创建JobDetailImpl，添加任务明细信息，注意这类的jdi.setJobClass((Class) jobClass)实际就是MethodInvokingJob。MethodInvokingJob也是我们最终要反射调用执行的内容。
- 源码177行： 初始化任务后赋值给this.jobDetail = jdi，也就是最终的类对象MethodInvokingJobDetailFactoryBean.getObject() @Override public JobDetail getObject() { return this.jobDetail; }
- 源码：220行： 获取对象时返回 this.jobDetail，这也就解释了为什么 MethodInvokingJobDetailFactoryBean 初始化后直接赋值给了一个 JobDetail ；
3. 定义执行计划(CronTriggerFactoryBeann)
// 定义了；执行的计划
CronTriggerFactoryBean cronTriggerFactoryBean = new CronTriggerFactoryBean();
cronTriggerFactoryBean.setJobDetail(methodInvokingJobDetailFactoryBean.getObject());
cronTriggerFactoryBean.setCronExpression("0/5 * * * * ?");
cronTriggerFactoryBean.setName("demoTask");
cronTriggerFactoryBean.afterPropertiesSet();
这一块主要定义任务的执行计划，并将任务执行内容交给 CronTriggerFactoryBean 管理，同时设置必要信息；
- jobDetail：设置任务体，xml 中可以直接将对象赋值，硬编码中设置执行的 JobDetail 对象信息。也就是我们上面设置的 JobDetailImpl ，通过 getObject() 获取出来。
- cronExpression：计划表达式；秒、分、时、日、月、周、年
CronTriggerFactoryBean.afterPropertiesSet()
@Override
public void afterPropertiesSet() throws ParseException {
// ... 校验属性信息
CronTriggerImpl cti = new CronTriggerImpl();
cti.setName(this.name);
cti.setGroup(this.group);
if (this.jobDetail != null) {
cti.setJobKey(this.jobDetail.getKey());
}
cti.setJobDataMap(this.jobDataMap);
cti.setStartTime(this.startTime);
cti.setCronExpression(this.cronExpression);
cti.setTimeZone(this.timeZone);
cti.setCalendarName(this.calendarName);
cti.setPriority(this.priority);
cti.setMisfireInstruction(this.misfireInstruction);
cti.setDescription(this.description);
this.cronTrigger = cti;
}
- 源码237行： 创建触发器 CronTriggerImpl 并设置相关属性信息
- 源码245行： 生成执行计划类 cti.setCronExpression(this.cronExpression);
public void setCronExpression(String cronExpression) throws ParseException {
TimeZone origTz = getTimeZone();
this.cronEx = new CronExpression(cronExpression);
this.cronEx.setTimeZone(origTz);
}CronExpression.java & 解析Cron表达式
protected void buildExpression(String expression) throws ParseException {
expressionParsed = true;
try {
// ... 初始化 TreeSet xxx = new TreeSet<Integer>();
int exprOn = SECOND;
StringTokenizer exprsTok = new StringTokenizer(expression, " \t",
false);
while (exprsTok.hasMoreTokens() && exprOn <= YEAR) {
String expr = exprsTok.nextToken().trim();
// ... 校验DAY_OF_MONTH和DAY_OF_WEEK字段的特殊字符
StringTokenizer vTok = new StringTokenizer(expr, ",");
while (vTok.hasMoreTokens()) {
String v = vTok.nextToken();
storeExpressionVals(0, v, exprOn);
}
exprOn++;
}
// ... 校验DAY_OF_MONTH和DAY_OF_WEEK字段的特殊字符
} catch (ParseException pe) {
throw pe;
} catch (Exception e) {
throw new ParseException("Illegal cron expression format ("
+ e.toString() + ")", 0);
}
}- Cron表达式有7个字段，CronExpression 把7个字段解析为7个 TreeSet 对象。填充TreeSet对象值的时候，表达式都会转换为起始值、结束值和增量的计算模式，然后计算出匹配的值放进TreeSet对象
CronTriggerFactoryBean.getObject()
@Override
public CronTrigger getObject() {
return this.cronTrigger;
}
- 源码257行： 获取对象时返回 this.cronTrigger ，也就是 CronTriggerImpl 对象
4. 调度执行计划(SchedulerFactoryBean)
// 调度了；执行的计划(scheduler)
SchedulerFactoryBean schedulerFactoryBean = new SchedulerFactoryBean();
schedulerFactoryBean.setTriggers(cronTriggerFactoryBean.getObject());
schedulerFactoryBean.setAutoStartup(true);
schedulerFactoryBean.afterPropertiesSet();
schedulerFactoryBean.start();
这一部分如名字一样调度工厂，相当于一个指挥官，可以从全局做调度，比如监听哪些trigger已经ready、分配线程等等，同样也需要设置必要的属性信息；
- triggers：按需可以设置多个触发器，本文设置了一个 cronTriggerFactoryBean.getObject() 也就是 CronTriggerImpl 对象
- autoStartup：默认是否自动启动任务，默认值为true
这个过程较长包括：调度工厂、线程池、注册任务等等，整体核心加载流程如下；
- 整个加载过程较长，抽取部分核心代码块进行分析，其中包括的类；
- StdScheduler
- StdSchedulerFactory
- SimpleThreadPool
- QuartzScheduler
- QuartzSchedulerThread
- RAMJobStore
- CronTriggerImpl
- CronExpression
SchedulerFactoryBean.afterPropertiesSet()
public void afterPropertiesSet() throws Exception {
if (this.dataSource == null && this.nonTransactionalDataSource != null) {
this.dataSource = this.nonTransactionalDataSource;
}
if (this.applicationContext != null && this.resourceLoader == null) {
this.resourceLoader = this.applicationContext;
}
// Initialize the Scheduler instance...
this.scheduler = prepareScheduler(prepareSchedulerFactory());
try {
registerListeners();
registerJobsAndTriggers();
}
catch (Exception ex) {
try {
this.scheduler.shutdown(true);
}
catch (Exception ex2) {
logger.debug("Scheduler shutdown exception after registration failure", ex2);
}
throw ex;
}
}
- 源码474行： 为调度器做准备工作 prepareScheduler(prepareSchedulerFactory()) ，
- SchedulerFactoryBean.prepareScheduler(SchedulerFactory schedulerFactory)
- SchedulerFactoryBean.createScheduler(schedulerFactory, this.schedulerName);
- SchedulerFactoryBean.createScheduler(SchedulerFactory schedulerFactory, String schedulerName)
- Scheduler newScheduler = schedulerFactory.getScheduler();
- StdSchedulerFactory.getScheduler();
- sched = instantiate(); 包括一系列核心操作；
1）初始化threadPool(线程池)：开发者可以通过org.quartz.threadPool.class配置指定使用哪个线程池类，比如SimpleThreadPool。
2）初始化jobStore(任务存储方式)：开发者可以通过org.quartz.jobStore.class配置指定使用哪个任务存储类，比如RAMJobStore。
3）初始化dataSource(数据源)：开发者可以通过org.quartz.dataSource配置指定数据源详情，比如哪个数据库、账号、密码等。
4）初始化其他配置：包括SchedulerPlugins、JobListeners、TriggerListeners等；
5）初始化threadExecutor(线程执行器)：默认为DefaultThreadExecutor；
6）创建工作线程：根据配置创建N个工作thread，执行start()启动thread，并将N个thread顺序add进threadPool实例的空闲线程列表availWorkers中；
7）创建调度器线程：创建QuartzSchedulerThread实例，并通过threadExecutor.execute(实例)启动调度器线程；
8）创建调度器：创建StdScheduler实例，将上面所有配置和引用组合进实例中，并将实例存入调度器池中- 源码477行： 调用父类 SchedulerAccessor.registerJobsAndTriggers() 注册任务和触发器 for (Trigger trigger : this.triggers) { addTriggerToScheduler(trigger); }
SchedulerAccessor.addTriggerToScheduler() & SchedulerAccessor 是SchedulerFactoryBean的父类
private boolean addTriggerToScheduler(Trigger trigger) throws SchedulerException {
boolean triggerExists = (getScheduler().getTrigger(trigger.getKey()) != null);
if (triggerExists && !this.overwriteExistingJobs) {
return false;
}
// Check if the Trigger is aware of an associated JobDetail.
JobDetail jobDetail = (JobDetail) trigger.getJobDataMap().remove("jobDetail");
if (triggerExists) {
if (jobDetail != null && !this.jobDetails.contains(jobDetail) && addJobToScheduler(jobDetail)) {
this.jobDetails.add(jobDetail);
}
try {
getScheduler().rescheduleJob(trigger.getKey(), trigger);
}
catch (ObjectAlreadyExistsException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Unexpectedly encountered existing trigger on rescheduling, assumably due to " +
"cluster race condition: " + ex.getMessage() + " - can safely be ignored");
}
}
}
else {
try {
if (jobDetail != null && !this.jobDetails.contains(jobDetail) &&
(this.overwriteExistingJobs || getScheduler().getJobDetail(jobDetail.getKey()) == null)) {
getScheduler().scheduleJob(jobDetail, trigger);
this.jobDetails.add(jobDetail);
}
else {
getScheduler().scheduleJob(trigger);
}
}
catch (ObjectAlreadyExistsException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Unexpectedly encountered existing trigger on job scheduling, assumably due to " +
"cluster race condition: " + ex.getMessage() + " - can safely be ignored");
}
if (this.overwriteExistingJobs) {
getScheduler().rescheduleJob(trigger.getKey(), trigger);
}
}
}
return true;
}
- 源码299行： addJobToScheduler(jobDetail) 一直会调用到 RAMJobStore 进行存放任务信息到 HashMap<JobKey, JobWrapper>(100)
public void storeJob(JobDetail newJob,
boolean replaceExisting) throws ObjectAlreadyExistsException {
JobWrapper jw = new JobWrapper((JobDetail)newJob.clone());
boolean repl = false;
synchronized (lock) {
if (jobsByKey.get(jw.key) != null) {
if (!replaceExisting) {
throw new ObjectAlreadyExistsException(newJob);
}
repl = true;
}
if (!repl) {
// get job group
HashMap<JobKey, JobWrapper> grpMap = jobsByGroup.get(newJob.getKey().getGroup());
if (grpMap == null) {
grpMap = new HashMap<JobKey, JobWrapper>(100);
jobsByGroup.put(newJob.getKey().getGroup(), grpMap);
}
// add to jobs by group
grpMap.put(newJob.getKey(), jw);
// add to jobs by FQN map
jobsByKey.put(jw.key, jw);
} else {
// update job detail
JobWrapper orig = jobsByKey.get(jw.key);
orig.jobDetail = jw.jobDetail; // already cloned
}
}
}- 初始化线程组；
- prepareScheduler
- createScheduler
- schedulerFactory
- StdSchedulerFactory.getScheduler()
- getScheduler()->instantiate()
- 源码1323行： tp.initialize();
SimpleThreadPool.initialize() & 这里的count是默认配置中的数量，可以更改
// create the worker threads and start them
Iterator<WorkerThread> workerThreads = createWorkerThreads(count).iterator();
while(workerThreads.hasNext()) {
WorkerThread wt = workerThreads.next();
wt.start();
availWorkers.add(wt);
}5. 启动定时任务
案例中使用硬编码方式调用 schedulerFactoryBean.start() 启动线程服务。线程的协作通过Object sigLock来实现，关于sigLock.wait()方法都在QuartzSchedulerThread的run方法里面，所以sigLock唤醒的是只有线程QuartzSchedulerThread。核心流程如下；
这个启动过程中，核心的代码类，如下；
- StdScheduler
- QuartzScheduler
- QuartzSchedulerThread
- ThreadPool
- RAMJobStore
- CronTriggerImpl
- JobRunShellFactory
QuartzScheduler.start() & 启动
public void start() throws SchedulerException {
if (shuttingDown|| closed) {
throw new SchedulerException(
"The Scheduler cannot be restarted after shutdown() has been called.");
}
// QTZ-212 : calling new schedulerStarting() method on the listeners
// right after entering start()
notifySchedulerListenersStarting();
if (initialStart == null) {
initialStart = new Date();
this.resources.getJobStore().schedulerStarted();
startPlugins();
} else {
resources.getJobStore().schedulerResumed();
}
// 唤醒线程
schedThread.togglePause(false);
getLog().info(
"Scheduler " + resources.getUniqueIdentifier() + " started.");
notifySchedulerListenersStarted();
}
QuartzSchedulerThread.run() & 执行过程
@Override
public void run() {
int acquiresFailed = 0;
// 只有调用了halt()方法，才会退出这个死循环
while (!halted.get()) {
try {
// 一、如果是暂停状态，则循环超时等待1000毫秒
// wait a bit, if reading from job store is consistently failing (e.g. DB is down or restarting)..
// 阻塞直到有空闲的线程可用并返回可用的数量
int availThreadCount = qsRsrcs.getThreadPool().blockForAvailableThreads();
if(availThreadCount > 0) {
List<OperableTrigger> triggers;
long now = System.currentTimeMillis();
clearSignaledSchedulingChange();
try {
// 二、获取acquire状态的Trigger列表，也就是即将执行的任务
triggers = qsRsrcs.getJobStore().acquireNextTriggers(
now + idleWaitTime, Math.min(availThreadCount, qsRsrcs.getMaxBat
acquiresFailed = 0;
if (log.isDebugEnabled())
log.debug("batch acquisition of " + (triggers == null ? 0 : triggers
} catch(){//...}
if (triggers != null && !triggers.isEmpty()) {
// 三：获取List第一个Trigger的下次触发时刻
long triggerTime = triggers.get(0).getNextFireTime().getTime();
// 四：获取任务触发集合
List<TriggerFiredResult> res = qsRsrcs.getJobStore().triggersFired(triggers);
// 五：设置Triggers为'executing'状态
qsRsrcs.getJobStore().releaseAcquiredTrigger(triggers.get(i));
// 六：创建JobRunShell
qsRsrcs.getJobRunShellFactory().createJobRunShell(bndle);
// 七：执行Job
qsRsrcs.getThreadPool().runInThread(shell)
continue; // while (!halted)
}
} else { // if(availThreadCount > 0)
// should never happen, if threadPool.blockForAvailableThreads() follows con
continue; // while (!halted)
}
} catch(RuntimeException re) {
getLog().error("Runtime error occurred in main trigger firing loop.", re);
}
}
qs = null;
qsRsrcs = null;
}
- 源码391行： 创建JobRunShell，JobRunShell实例在initialize()方法就会把包含业务逻辑类的JobDetailImpl设置为它的成员属性，为后面执行业务逻辑代码做准备。执行业务逻辑代码在runInThread(shell)方法里面。
- QuartzSchedulerThread.run() & 部分代码
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;
}- 源码398行： qsRsrcs.getThreadPool().runInThread(shell)
- SimpleThreadPool.runInThread
// 保存所有WorkerThread的集合
private List<WorkerThread> workers;
// 空闲的WorkerThread集合
private LinkedList<WorkerThread> availWorkers = new LinkedList<WorkerThread>();
// 任务的WorkerThread集合
private LinkedList<WorkerThread> busyWorkers = new LinkedList<WorkerThread>();
/**
* 维护workers、availWorkers和busyWorkers三个列表数据
* 有任务需要一个线程出来执行：availWorkers.removeFirst();busyWorkers.add()
* 然后调用WorkThread.run(runnable)方法
*/
public boolean runInThread(Runnable runnable) {
if (runnable == null) {
return false;
}
synchronized (nextRunnableLock) {
handoffPending = true;
// Wait until a worker thread is available
while ((availWorkers.size() < 1) && !isShutdown) {
try {
nextRunnableLock.wait(500);
} catch (InterruptedException ignore) {
}
}
if (!isShutdown) {
WorkerThread wt = (WorkerThread)availWorkers.removeFirst();
busyWorkers.add(wt);
wt.run(runnable);
} else {
// If the thread pool is going down, execute the Runnable
// within a new additional worker thread (no thread from the pool).
WorkerThread wt = new WorkerThread(this, threadGroup,
"WorkerThread-LastJob", prio, isMakeThreadsDaemons(), runnable);
busyWorkers.add(wt);
workers.add(wt);
wt.start();
}
nextRunnableLock.notifyAll();
handoffPending = false;
}
return true;
}- 源码428行： WorkerThread ，是一个内部类，主要是赋值并唤醒lock对象的等待线程队列
- WorkerThread.run(Runnable newRunnable)
public void run(Runnable newRunnable) {
synchronized(lock) {
if(runnable != null) {
throw new IllegalStateException("Already running a Runnable!");
}
runnable = newRunnable;
lock.notifyAll();
}
}- 源码561行： WorkerThread 的run方法，方法执行lock.notifyAll()后，对应的WorkerThread就会来到run()方法。到这！接近曙光了！终于来到了执行业务的execute()方法的倒数第二步，runnable对象是一个JobRunShell对象，下面在看JobRunShell.run()方法。
- WorkerThread.run()
@Override
public void run() {
boolean ran = false;
while (run.get()) {
try {
synchronized(lock) {
while (runnable == null && run.get()) {
lock.wait(500);
}
if (runnable != null) {
ran = true;
// 启动真正执行的内容，runnable就是JobRunShell
runnable.run();
}
}
} cache(){//...}
}
//if (log.isDebugEnabled())
try {
getLog().debug("WorkerThread is shut down.");
} catch(Exception e) {
// ignore to help with a tomcat glitch
}
}JobRunShell.run() & 从上面WorkerThread.run()，调用到这里执行
public void run() {
qs.addInternalSchedulerListener(this);
try {
OperableTrigger trigger = (OperableTrigger) jec.getTrigger();
JobDetail jobDetail = jec.getJobDetail();
do {
// ...
long startTime = System.currentTimeMillis();
long endTime = startTime;
// execute the job
try {
log.debug("Calling execute on job " + jobDetail.getKey());
// 执行业务代码，也就是我们的task
job.execute(jec);
endTime = System.currentTimeMillis();
} catch (JobExecutionException jee) {
endTime = System.currentTimeMillis();
jobExEx = jee;
getLog().info("Job " + jobDetail.getKey() +
" threw a JobExecutionException: ", jobExEx);
} catch (Throwable e) {
endTime = System.currentTimeMillis();
getLog().error("Job " + jobDetail.getKey() +
" threw an unhandled Exception: ", e);
SchedulerException se = new SchedulerException(
"Job threw an unhandled exception.", e);
qs.notifySchedulerListenersError("Job ("
+ jec.getJobDetail().getKey()
+ " threw an exception.", se);
jobExEx = new JobExecutionException(se, false);
}
jec.setJobRunTime(endTime - startTime);
// 其他代码
} while (true);
} finally {
qs.removeInternalSchedulerListener(this);
}
}
QuartzJobBean.execte() & 继续往下走
public final void execute(JobExecutionContext context) throws JobExecutionException {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
MutablePropertyValues pvs = new MutablePropertyValues();
pvs.addPropertyValues(context.getScheduler().getContext());
pvs.addPropertyValues(context.getMergedJobDataMap());
bw.setPropertyValues(pvs, true);
}
catch (SchedulerException ex) {
throw new JobExecutionException(ex);
}
executeInternal(context);
}
MethodInvokingJobDetailFactoryBean->MethodInvokingJob.executeInternal(JobExecutionContext context)
protected void executeInternal(JobExecutionContext context) throws JobExecutionException {
try {
// 反射执行业务代码
context.setResult(this.methodInvoker.invoke());
}
catch (InvocationTargetException ex) {
if (ex.getTargetException() instanceof JobExecutionException) {
// -> JobExecutionException, to be logged at info level by Quartz
throw (JobExecutionException) ex.getTargetException();
}
else {
// -> "unhandled exception", to be logged at error level by Quartz
throw new JobMethodInvocationFailedException(this.methodInvoker, ex.getTargetException());
}
}
catch (Exception ex) {
// -> "unhandled exception", to be logged at error level by Quartz
throw new JobMethodInvocationFailedException(this.methodInvoker, ex);
}
}
五、综上总结
- quartz，即石英的意思，隐喻如石英钟般对时间的准确把握。
- 源码分析是一个很快乐的过程，这个快乐是分析完才能获得的快乐。纵横交互的背后是面向对象的高度解耦，对线程精彩的使用，将任务执行做成计划单，简直是一个超级棒的作品。
- 对于quartz.properties，简单场景下，开发者不用自定义配置，使用quartz默认配置即可，但在要求较高的使用场景中还是要自定义配置，比如通过org.quartz.threadPool.threadCount设置足够的线程数可提高多job场景下的运行性能。
- quartz 对任务处理高度解耦，job与trigger解藕，将任务本身和任务执行策略解藕，这样可以方便实现N个任务和M个执行策略自由组合。
- scheduler单独分离出来，相当于一个指挥官，可以从全局做调度，比如监听哪些trigger已经ready、分配线程等等。
- 外部链接：
http://www.quartz-scheduler.org
quartz-2.1.x/configuration
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