原文地址:http://smurfs.iteye.com/blog/1155965
任何个人、任何企业、任何行业都会有作业调度的需求。举几个简单的例子:
1、每个月都会发工资,每个月都要报销等;
2、每个人每天都要吃饭和睡觉;
3、每个公司都有会计帐期,都需要向公司领导汇报月报、季报、年报等。
4、银行和金融行业每天都需要日切等等。
对于个人,对作业调度的感知不是非常明确,但对于一个企业,一个好的作业调度可以为企业节省很多时间和金钱。俗话说,时间就是金钱,过高的资源投入到枯燥的任务中无疑是金钱和资源的浪费,随着业务流程复杂性的提高,自动化流程和自动化作业调度更能凸显出益处来。之所以自动化的出现,因为在做重复性工作时,人的效率和正确率远低于电脑。把一系列任务自动安排到一个作业中,然后再为这个作业创建一个调度器,到时候这个作业就会自动执行了。
Quartz是经典的作业调度框架,在深入研究之初,先仿照quartz的原理,设计一个简单的作业调度器,类图如下:
![](https://img.laitimes.com/img/_0nNw4CM6IyYiwiM6ICdiwiIyVGduV2QvwVe0lmdhJ3ZvwFM38CXlZHbvN3cpR2Lc1TPB10QGtWUCpEMJ9CXsxWam9CXwADNvwVZ6l2c052bm9CXUJDT1wkNhVzLcRnbvZ2LcZXUYpVd1kmYr50MZV3YyI2cKJDT29GRjBjUIF2LcRHelR3LcJzLctmch1mclRXY39zM4QjMzATM3EDNxgDM1EDMy8CX0Vmbu4GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.jpg)
1、 先看job类,这个类,非常简单,只有一个execute方法,该方法是job具体执行的内容:
public void execute(Map<String, String> jobData) {
System.out.println("####################");
System.out.println(jobData.get("type") + ":Test Job Run at :" + System.currentTimeMillis());
System.out.println("####################");
}
2、 jobdetail类,该类是对具体job类的封装,包括jobName(id),job执行需要的运行时参数,在名为jobdata的hashMap中
private Class<? extends Job> clazz;
private String jobName;
private HashMap<String, String> jobData;
public JobDetail() {
jobData = new HashMap<String, String>();
}
public JobDetail(String name, Class<? extends Job> clazz) {
this();
this.jobName = name;
this.clazz = clazz;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((jobName == null) ? 0 : jobName.hashCode());
return result;
}
/*
* (non-Javadoc)
*
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
JobDetail other = (JobDetail) obj;
if (jobName == null) {
if (other.jobName != null)
return false;
} else if (!jobName.equals(other.jobName))
return false;
return true;
}
3、 trigger类,记录下次运行作业的时间和运行job的key:
private String jobKey;
private long nextFireTime;
@Override
public int compareTo(Trigger o) {// 在treemap中可以根据下次运行时间排序
return (int) (this.nextFireTime - o.getNextFireTime());
}
public void resert() {
setNextFireTime(-1);// 测试是只想运行一次,使用-1来退出
}
4、 scheduler类,最重要的类,用来启动和停止框架
private List<JobDetail> jobList = new ArrayList<JobDetail>();
private TreeSet<Trigger> triggerList = new TreeSet<Trigger>();
private Object lockObj = new Object();
SchedulerThread thread = new SchedulerThread();// 任务调度在本此线程执行
public void schedulerJob(JobDetail detail, Trigger trigger) {
synchronized (lockObj) {
jobList.add(detail);
trigger.setJobKey(detail.getJobName());
triggerList.add(trigger);
}
}
public void start() {
System.out.println("########## run scheduler at :" + new Date() + "##########");
thread.start();
}
public void halt() {
thread.halt();
}
5、 scheduler的执行是在scheduler的schedulerThread中执行;线程中最重要的是run方法体,另外还有一个halt方法用来停止线程。先看halt方法
private boolean shutDown = false;
public void halt() {// 停止线程
synchronized (lockObj) {
shutDown = true;
lockObj.notifyAll();
}
}
Run方法体为:
public void run() {// 运行
<span style="white-space:pre"> </span>while (!shutDown)
synchronized (lockObj) {
<span style="white-space:pre"> </span> try {
final Trigger trigger = triggerList.pollFirst();// 获取最近执行的作业
<span style="white-space:pre"> </span> if (trigger == null) {
lockObj.wait(100);
continue;
}
long curr = System.currentTimeMillis();
long nextTime = trigger.getNextFireTime();
while (nextTime > curr && !shutDown) {
curr = System.currentTimeMillis();
if (nextTime > curr + 1) {
lockObj.wait(nextTime - curr);
}
if (!shutDown) {
int index = jobList.indexOf(new JobDetail(trigger.getJobKey(), null));
JobDetail jobDetail = jobList.get(index);
Job job = jobDetail.getClazz().newInstance();
job.execute(jobDetail.getJobData());
trigger.resert();
nextTime = trigger.getNextFireTime();
if (nextTime != -1) {
triggerList.add(trigger);
} else {
break;
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
至此所有的框架代码都已经完成。注:没有考虑NullPointException和多线程问题。
再看下测试代码:
public static void main(String[] args) throws Exception {
final JobDetail detail1 = new JobDetail("job1", Job.class) {
{
getJobData().put("type", "job1");
}
};
final JobDetail detail2 = new JobDetail("job2", Job.class) {
{
getJobData().put("type", "job2");
}
};
final Trigger trigger1 = new Trigger() {
{
setNextFireTime(System.currentTimeMillis() + 3000l);
}
};
final Trigger trigger2 = new Trigger() {
{
setNextFireTime(System.currentTimeMillis() + 1000l);
}
};
Scheduler scheduler = new Scheduler();
scheduler.schedulerJob(detail1, trigger1);
scheduler.schedulerJob(detail2, trigger2);
scheduler.start();
Thread.sleep(10000l);
scheduler.halt();
}
结果
########## run scheduler at :Fri Aug 14 17:09:42 CST 2015##########
####################
job2:Test Job Run at :1439543383133
####################
####################
job1:Test Job Run at :1439543385133
####################
系统按照下次运行时间来执行,并成功显示结果。
本章只是在抽取quartz的核心处理逻辑的基础智商,去除安全验证和多线程同步问题编写的基本调度任务。仅为抛砖引玉,为quartz源码的解析打个基础。
源码地址:https://github.com/luyanliang/quartz_demo.git