Two implementation methods of Spring timer in JAVA

There are currently two popular Spring timer configurations: Java's Timer class and OpenSymphony's Quartz.

1.Java Timer timing

First inherit the java.util.TimerTask class to implement the run method

import java.util.TimerTask; 
public class EmailReportTask extends TimerTask{ 
  @Override 
  public void run() { 
    ... 
  }  
}

defined in Spring

...

Configure the Spring timer

<bean id="scheduleReportTask" class="org.springframework.scheduling.timer.ScheduledTimerTask"> 
<property name="timerTask" ref="reportTimerTask" /> 
<property name="period"> 
<value>86400000value> 
property> 
bean>

timerTask attribute tells Scheduled TimerTask Which one to run. 86400000 represents 24 hours

Start the Spring timer

Spring's TimerFactoryBean is responsible for starting scheduled tasks

<bean class="org.springframework.scheduling.timer.TimerFactoryBean"> 
<property name="scheduledTimerTasks"> 
  <list><ref bean="scheduleReportTask"/>list> 
property> 
bean>

scheduledTimerTasks displays a list of timer tasks that need to be started.

You can delay the start by setting the delay attribute

<bean id="scheduleReportTask" class="org.springframework.scheduling.timer.ScheduledTimerTask"> 
<property name="timerTask" ref="reportTimerTask" /> 
<property name="period"> 
<value>86400000value> 
property> 
<property name="delay"> 
<value>3600000value> 
property> 
bean>

We can only stipulate that this task should be run every 24 hours, and it cannot be started at a certain time

2.Quartz timer

First inherit the QuartzJobBean class to implement executeInternal Method

import org.quartz.JobExecutionContext; 
import org.quartz.JobExecutionException; 
import org.springframework.scheduling.quartz.QuartzJobBean; 
public class EmailReportJob extends QuartzJobBean{ 
protected void executeInternal(JobExecutionContext arg0) 
throws JobExecutionException { 
... 
} 
}

is defined in Spring

<bean id="reportJob" class="org.springframework.scheduling.quartz.JobDetailBean"> 
<property name="jobClass"> 
<value>EmailReportJobvalue> 
property> 
<property name="jobDataAsMap"> 
  <map> 
    <entry key="courseService"> 
      <ref bean="courseService"/> 
      entry> 
  map> 
property> 
bean>

Here we do not directly declare an EmailReportJob Bean, but declare a JobDetailBean. This is a characteristic of Quartz. JobDetailBean is a subclass of Quartz's org.quartz.JobDetail, which requires setting a Job object through the jobClass attribute.

Another special thing about using Quartz's JobDetail is that the courseService attribute of EmailReportJob is set indirectly. The jobDataAsMap property of JobDetail accepts a Map, including various attributes set to jobClass. When JobDetailBean is instantiated, it injects the courseService Bean into the courseService property of EmailReportJob.

Start timer

Quartz’s org.quartz.Trigger class describes when and how often to run a Quartz job. Spring provides two triggers SimpleTriggerBean and CronTriggerBean.

SimpleTriggerBean is similar to scheduledTimerTasks. Specify the execution frequency of the job, imitating the scheduledTimerTasks configuration.

<bean id="simpleReportTrigger" class="org.springframework.scheduling.quartz.SimpleTriggerBean"> 
<property name="jobDetail" ref="reprotJob" /> 
<property name="startDelay"> 
<value>360000value> 
property> 
<property name="repeatInterval"> 
  <value>86400000value> 
property> 
bean>

startDelay is also delayed for 1 hour to start

CronTriggerBean specifies the exact running time of the job

<bean id="cronReportTrigger" class="org.springframework.scheduling.quartz.CronTriggerBean"> 
<property name="jobDetail" ref="reprotJob" /> 
<property name="cronExpression"> 
<value>0 0 6 * * ?value> 
property> 
bean>

The attribute cronExpression tells when to trigger. The most mysterious thing is the cron expression:

Cron is usually responsible for scheduled tasks in Linux systems. A cron expression has at least 6 (possibly 7) space-separated time elements. From left to right:

1. Second 2. Minute 3. Hour 4. Day of the month (1-31) 5. Month (1-12 or JAN-DEC) 6. Day of the week (1-7 or SUN-SAT) 7. Year (1970-2099)
Each element displays a value (such as 6), an interval (9-12), a list (9, 11, 13) or a wildcard (*) . Because the two elements 4 and 6 are mutually exclusive, you should set a question mark (?) to indicate the field you do not want to set, and "/" if the value combination indicates the number of repetitions (10/6 means repeating 6 every 10 seconds Second-rate).

Start timer

<bean class="org.springframework.scheduling.quartz.SchedulerFactoryBean"> 
  <property name="triggers"> 
    <list><ref bean="cronReportTrigger"/>list> 
  property> 
bean>

triggers property accepts a set of triggers.

Okay, that’s the end of this article. It’s pretty good, but there are some deficiencies. You are welcome to give me your valuable opinions.

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