please tell me the meaning of "0 * * * * ?" at cronExpression.
<bean id="batchJobTrigger" class="org.springframework.scheduling.quartz.CronTriggerFactoryBean">
<property name="jobDetail" ref="batchJobDetail"/>
<property name="cronExpression">
<value>0 * * * * ?</value>
</property>
</bean>
Second Minute Hour Day-of-month Month Day-of-week Year (optional)
0 * * * * First second of every minute of every hour of every day of every month
? Specifies no particular value. This is useful when you need to specify a value for one of the two fields Day-of-month or Day-of-week, but not the other.