Schedule at 24hrs interval

问题

I want to know the best method to schedule a code. I have a code that generates reports and sends mail to a set of people at interval of 24hrs. Its a console based java application. I want to know the best method to schedule that. Sometimes I may need to change that to 12hrs interval. However the application doesn't perform any other task in between the interval.

回答1:

Here are few approach, from simplest to most comprehensive:

sleep():
```
TimeUnit.HOURS.sleep(24)
```
This approach is very simple, do the work and sleep for 24 hours. Actually it is a bit more complex because the report generation takes some time, so you have to sleep slightly shorter. All solutions below handle this transparently.
java.util.Timer#scheduleAtFixedRate() - simple, built-in Java solution.
@Scheduled annotation in spring or @Schedule in ejb - more complex but also more powerful, e.g. accepts cron expressions:
```
@Scheduled(fixedRate=DateUtils.MILLIS_PER_DAY)
public void generateReport() {
  //...
}
```

quartz-scheduler - full blown Java scheduler with clustering and fail-over, misfire handling, full cron support, etc. Very comprehensive:

newTrigger().
  withSchedule(
    simpleSchedule().
      withIntervalInHours(24).
      repeatForever()
    ).build();

newTrigger().
  withSchedule(
    cronSchedule().
      dailyAtHourAndMinute(17, 30).  //17:30
    ).build();

回答2:

I am using two ways:

First for non managed code like client code: Chron4J

Second is implmented in the JavaEE framewoks. You can use it via annotating methods when you use an container like Glassfish/JBoss. Would be something like this:

@Schedule(second="*/1", minute="*",hour="*", persistent=false)
public void doWork(){
    System.out.println("timer: " + helloService.sayHello());
}

回答3:

I would take a look at the quartz scheduler if I were you. I used in a number of applications and it's really easy to use. You can find more information here: http://quartz-scheduler.org/

If you use the spring stack I would surely recommend it, since it is super easy to configure in xml and let spring inject all the stuff for you.

回答4:

Well, if the program can be idle try something like this

try
{
for (;;) {
    //code
    Thread.sleep(1000 * 60 * 60 * 24);
    //code
    }
}
catch(Exception e)
{
     System.out.println(e);
}

来源：https://stackoverflow.com/questions/9618027/schedule-at-24hrs-interval

标签

java

multithreading