How to schedule a periodic task in Java?

Question

I need to schedule a task to run in at fixed interval of time. How can I do this with support of long intervals (for example on each 8 hours)?

I'm currently using java.util.Timer.scheduleAtFixedRate . Does java.util.Timer.scheduleAtFixedRate support long time intervals?

Answer 1

Use a ScheduledExecutorService :

 private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
 scheduler.scheduleAtFixedRate(yourRunnable, 8, 8, TimeUnit.HOURS);

Answer 2

您应该看看Quartz，它是一个 Java 框架，可与 EE 和 SE 版本一起使用，并允许定义作业以执行特定时间

Answer 3

Try this way ->

Firstly create a class TimeTask that run your task, it looks like:

public class CustomTask extends TimerTask  {

   public CustomTask(){

     //Constructor

   }

   public void run() {
       try {

         // Your task process

       } catch (Exception ex) {
           System.out.println("error running thread " + ex.getMessage());
       }
    }
}

then in main class you instantiate the task and run it periodically started by a specified date:

 public void runTask() {

        Calendar calendar = Calendar.getInstance();
        calendar.set(
           Calendar.DAY_OF_WEEK,
           Calendar.MONDAY
        );
        calendar.set(Calendar.HOUR_OF_DAY, 15);
        calendar.set(Calendar.MINUTE, 40);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);



        Timer time = new Timer(); // Instantiate Timer Object

        // Start running the task on Monday at 15:40:00, period is set to 8 hours
        // if you want to run the task immediately, set the 2nd parameter to 0
        time.schedule(new CustomTask(), calendar.getTime(), TimeUnit.HOURS.toMillis(8));
}

Answer 4

Use Google Guava AbstractScheduledService as given below:

public class ScheduledExecutor extends AbstractScheduledService {

   @Override
   protected void runOneIteration() throws Exception {
      System.out.println("Executing....");
   }

   @Override
   protected Scheduler scheduler() {
        return Scheduler.newFixedRateSchedule(0, 3, TimeUnit.SECONDS);
   }

   @Override
   protected void startUp() {
       System.out.println("StartUp Activity....");
   }


   @Override
   protected void shutDown() {
       System.out.println("Shutdown Activity...");
   }

   public static void main(String[] args) throws InterruptedException {
       ScheduledExecutor se = new ScheduledExecutor();
       se.startAsync();
       Thread.sleep(15000);
       se.stopAsync();
   }
}

If you have more services like this, then registering all services in ServiceManager will be good as all services can be started and stopped together. Read here for more on ServiceManager.

Answer 5

If you want to stick with java.util.Timer , you can use it to schedule at large time intervals. You simply pass in the period you are shooting for. Check the documentation here .

Answer 6

如果您的应用程序已经在使用 Spring 框架，那么您已经内置了调度

Answer 7

I use Spring Framework's feature. ( spring-context jar or maven dependency).

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;


@Component
public class ScheduledTaskRunner {

    @Autowired
    @Qualifier("TempFilesCleanerExecution")
    private ScheduledTask tempDataCleanerExecution;

    @Scheduled(fixedDelay = TempFilesCleanerExecution.INTERVAL_TO_RUN_TMP_CLEAN_MS /* 1000 */)
    public void performCleanTempData() {
        tempDataCleanerExecution.execute();
    }

}

ScheduledTask is my own interface with my custom method execute , which I call as my scheduled task.

Answer 8

Do something every one second

Timer timer = new Timer();
timer.schedule(new TimerTask() {
    @Override
    public void run() {
        //code
    }
}, 0, 1000);

Answer 9

These two classes can work together to schedule a periodic task:

Scheduled Task

import java.util.TimerTask;
import java.util.Date;

// Create a class extending TimerTask
public class ScheduledTask extends TimerTask {
    Date now; 
    public void run() {
        // Write code here that you want to execute periodically.
        now = new Date();                      // initialize date
        System.out.println("Time is :" + now); // Display current time
    }
}

Run Scheduled Task

import java.util.Timer;

public class SchedulerMain {
    public static void main(String args[]) throws InterruptedException {
        Timer time = new Timer();               // Instantiate Timer Object
        ScheduledTask st = new ScheduledTask(); // Instantiate SheduledTask class
        time.schedule(st, 0, 1000);             // Create task repeating every 1 sec
        //for demo only.
        for (int i = 0; i <= 5; i++) {
            System.out.println("Execution in Main Thread...." + i);
            Thread.sleep(2000);
            if (i == 5) {
                System.out.println("Application Terminates");
                System.exit(0);
            }
        }
    }
}

Reference https://www.mkyong.com/java/how-to-run-a-task-periodically-in-java/

Answer 10

Have you tried Spring Scheduler using annotations ?

@Scheduled(cron = "0 0 0/8 ? * * *")
public void scheduledMethodNoReturnValue(){
    //body can be another method call which returns some value.
}

you can do this with xml as well.

 <task:scheduled-tasks>
   <task:scheduled ref = "reference" method = "methodName" cron = "<cron expression here> -or- ${<cron expression from property files>}"
 <task:scheduled-tasks>

Answer 11

my servlet contains this as a code how to keep this in scheduler if a user presses accept

if(bt.equals("accept")) {
    ScheduledExecutorService scheduler=Executors.newScheduledThreadPool(1);
    String lat=request.getParameter("latlocation");
    String lng=request.getParameter("lnglocation");
    requestingclass.updatelocation(lat,lng);
}

Answer 12

java.util.concurrent 中有一个ScheduledFuture类，它可能对您有所帮助。