用石英更新JSP内容

Question

I'm currently working in Java EE (Eclipse Mars IDE)

The project is a dynamic website that uses an automatically triggering Job via Quartz to update its content on a daily basis. (I'm using a CronTrigger for this in Quartz)

There is no user posted content on the website, all I have is a list of Strings from which the scheduled Job chooses one String randomly. It should then set this chosen String as the content for the website's JSP.

What does work:

• The Quartz Job starts when the WAR file is deployed through a ServletContextListener, the Job also correctly chooses a new String to be the current content for the website

What does not work:

• When the Job triggers, the content on the website's .JSP should be updated to the most recently chosen String. I cannot get this to work.

What I am currently trying:

• I have a normal Servlet that gets the latest chosen String inside of the doPost method and sets this content as the attribute in the POST's request. I tried to return this request to the website and that works fine through a button with POST method. But I can't figure out how to do this programatically, aka from the scheduled Quartz Job.

Any suggestions for doing this better are very welcome and appreciated. I'm not a very experienced programmer (perhaps you could tell already) and the way I'm doing it now feels very... disorganized.

package model;

import java.util.Date;

import org.quartz.Job;
import org.quartz.JobExecutionContext;
import org.quartz.JobExecutionException;
import org.quartz.JobKey;
import org.quartz.SchedulerContext;
import org.quartz.SchedulerException;

public class RefreshQuoteJob implements Job {

    public void execute(JobExecutionContext context) throws JobExecutionException {
        System.out.println("[INFO] Executing refreshJob");
        JobKey jobKey = context.getJobDetail().getKey();
        SchedulerContext schedulerContext = null;
        System.out.println("[INFO] RefreshQuote says: " + jobKey + " executing at " + new Date());
        try {
            schedulerContext = context.getScheduler().getContext();
           } catch (SchedulerException e1) {
           e1.printStackTrace();
        }
        MediaHandler handler = (MediaHandler)schedulerContext.get("handler");
        //This selects the new String from the list, that string should be displayed on the JSP
        handler.refreshDB();
        //Update the content of the JSP here
        System.out.println("[INFO] refreshJob Executed");
    }
}

package model;

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

import java.util.Random;

import org.quartz.CronScheduleBuilder;
import org.quartz.CronTrigger;
import org.quartz.JobDetail;
import org.quartz.Scheduler;
import org.quartz.SchedulerException;
import org.quartz.SchedulerFactory;
import org.quartz.impl.StdSchedulerFactory;

public class RefreshQuoteTrigger {

    public SchedulerFactory sf;
    public Scheduler refreshSchedule;

    public void run(MediaHandler handler) throws SchedulerException {
        System.out.println("[INFO] Running RefreshTrigger");
        sf = new StdSchedulerFactory();
        Random randomPostingTime = new Random();
        refreshSchedule = sf.getScheduler();
        //sf.getScheduler().getContext().put("quoteDB", quoteDB);

        //I give the MediaHandler object to the job via this
        sf.getScheduler().getContext().put("handler", handler);

        JobDetail refreshJob = newJob(RefreshQuoteJob.class)
                .withIdentity("refreshJob", "group1")
                .build();

        //Handy?
        //.withSchedule(dailyAtHourAndMinute(07, (15+randomPostingTime.nextInt(59)))
        CronTrigger refreshTriggerDaily = newTrigger()
                .withIdentity("quoteRefreshSchedule", "group1")
                .withSchedule(CronScheduleBuilder.cronSchedule("0/"+randomPostingTime.nextInt(59)+" "+randomPostingTime.nextInt(7)+" 08 ? * *"))//This should mean it posts every day at 08:random minutes(between 0 and 7):random seconds(between 0 and 59)//0 15 10 ? * * //Every day at 10.15am
                .build();

        CronTrigger refreshTrigger = newTrigger()
                .withIdentity("quoteRefreshSchedule", "group1")
                .withSchedule(CronScheduleBuilder.cronSchedule("0/"+randomPostingTime.nextInt(59)+" * * * * ?"))//0 15 10 ? * * //Every day at 10.15am
                .build();


        refreshSchedule.scheduleJob(refreshJob, refreshTrigger);

        refreshSchedule.start();

        //This gives quartz 5 seconds to run its jobs and then sleeps the thread
        //In the final program I should give it enough time to run
        //Around Thread.sleep(300L * 1000L)
        try {
            Thread.sleep(30L * 1000L);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }


    public void forceShutdown() {
        try {
            refreshSchedule.shutdown(true);
        } catch (SchedulerException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

Answer 1

How are you trying to get the strings in your JSP? Are you able to access the Quartz context somehow? Even if you have, that would seem a bit contrived.

Normally for something like this you would use a Singleton that can be accessed from the Quartz job and from the JSP. How you access your Singleton depends on what technology you are using. You can use Spring, CDI, etc. You can also just have a static variable somewhere for a quick job:

public class MediaHandler {
    private static MediaHandler  instance = new MediaHandler ();
    public static MediaHandler getInstance() {return instance;}
}

Then from your Quartz job and Servlet you can access it:

MediaHandler handler=MediaHandler.getInstance();

Note: probably using a framework like Spring of CDI is a better idea in the long term.