How to run a Java program under cron and import the jars

Question

My source file is .../MyDir/proj/myProj.java. The jar files are under .../MyDir/proj/library. The jar files are from HTMLUnit 2.10.

This is the source for my cron file:

0 0 * * * java -classpath .../MyDir/proj/ myProj

But it gave me the error:

Exception in thread "main" java.lang.NoClassDefFoundError: com/gargoylesoftware/htmlunit/WebClient

How do I modify the cron file to import the jar files?

Answer 1

Something like this:

0 0 * * * java -classpath .../MyDir/proj/:.../MyDir/proj/library/jar1.jar:.../MyDir/proj/library/jar2.jar myProj

or if you are using a recent JVM you can use a wildcard to match all of the JAR files.

0 0 * * * java -classpath .../MyDir/proj/:.../MyDir/proj/library/\* myProj

(The backslash is probably unnecessary because 'globbing' is unlikely to match anything in that context ...)

---

Better still, put the command (and any others that need to be run to prepare for the launch) into a shell script, and run the script from your crontab entry instead.

Answer 2

It is very simple to implement the CRON Job in java

Required Library: quartz-2.0.0.jar

Scheduler Initiator:

import static org.quartz.JobBuilder.newJob;
import static org.quartz.TriggerBuilder.newTrigger;

import java.text.ParseException;

import org.quartz.CronScheduleBuilder;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.Trigger;
import org.quartz.impl.StdSchedulerFactory;

public class SchedulerListener{

    static Scheduler scheduler = null;
    public static void main(String[] args) {
        // Setup the Job class and the Job group
        JobDetail job = newJob(FileUploadToAzure.class).withIdentity(
                        "CronQuartzJob", "Group").build();

        // Create a Trigger that fires every hour.
        Trigger trigger;
        try {
            trigger = newTrigger()
            .withIdentity("TriggerName", "Group")
            .withSchedule(CronScheduleBuilder.cronSchedule("0 0 * * * ?"))
            .build();

            // Setup the Job and Trigger with Scheduler & schedule jobs
            scheduler = new StdSchedulerFactory().getScheduler();
            scheduler.start();
            scheduler.scheduleJob(job, trigger);

        } catch (ParseException | SchedulerException e) {
            e.printStackTrace();
        }


    }
} 

Scheduler Class:

import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;

public class SchedulerJob implements Job {
  @SuppressWarnings("unchecked")
    public void execute(JobExecutionContext context) throws JobExecutionException {
    System.out.println("Print at specific time");
}
}

CronTrigger Expression Meaning 0 0 12 * * ? Fire at 12pm (noon) every day 0 15 10 ? * * Fire at 10:15am every day 0 15 10 * * ? Fire at 10:15am every day 0 15 10 * * ? * Fire at 10:15am every day 0 15 10 * * ? 2005 Fire at 10:15am every day during the year 2005 0 * 14 * * ? Fire every minute starting at 2pm and ending at 2:59pm, every day 0 0/5 14 * * ? Fire every 5 minutes starting at 2pm and ending at 2:55pm, every day

More details about CRON Trigger, then please refer below link

http://www.askmani.net/question/crontrigger/

Answer 3

There is simple and better way that: you can copy all java statements used to run the Java application in to a linux script (runJavaApp.sh), then verify if it runs properly in any directory in Linux. If everything is OK. You can bind it to cron.

Answer 4

For Spring Boot Java users, you can use @scheduled annotation. For more details and a great example, visit this