Interrupt spring scheduler task before next invocation

Question

I have a Spring-Boot application which is going to be an orchestration service for several other processes we want to trigger. I have it currently set up using Spring Scheduling pulling crons dynamically from a database. I threw in a rest method to trigger the process to pull new cron information from the database. This logic all works correctly. The only "issue" is that it doesn't use the new cron information until the next scheduled run which gets to the real question. Is there a way to interrupt the current Trigger and schedule one again using the updated cron information. Here is the application for reference:

package com.bts.poc;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.TriggerContext;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.util.Date;

@SpringBootApplication
@EnableScheduling
@RestController
@RequestMapping("/APSCommon/Scheduling")
public class Application implements SchedulingConfigurer {

    @Autowired
    private DynamicCron dynamicCron;
    @Autowired
    PropertyManager propertyManager;

    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class);
    }

    private String cronConfig() {
        String cronTabExpression = propertyManager.getProperty("COMPANY", "JOB_NAME","CRON_EXPRESSION");
        return cronTabExpression;
    }

    @Override
    public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
        taskRegistrar.addTriggerTask(new Runnable() {
            @Override
            public void run() {
                dynamicCron.runJob();
            }
        }, new Trigger() {
            @Override
            public Date nextExecutionTime(TriggerContext triggerContext) {
                String cron = cronConfig();
                CronTrigger trigger = new CronTrigger(cron);
                Date nextExec = trigger.nextExecutionTime(triggerContext);
                DynamicCron.cronExpression = cron;
                return nextExec;
            }
        });
    }

    @RequestMapping(value = "/reloadScheduling", method = RequestMethod.GET)
    public String reloadScheduling() {
        PropertyManager.setResetProperties(true);
        return "schedules will be altered next run";
    }
}

Answer 1

So using SchedulingConfigurer->configureTasks you can't get access to the ScheduledFuture(s) in the Spring version I am using (4.2.7.RELEASE). From several posts I have read it has been mentioned as possible functionality for the future. I got around this by doing the following:

package com.bts.poc;

import com.bts.poc.service.DynamicCron;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.MessageSourceAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.web.bind.annotation.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.ArrayList;
import java.util.List;
import java.util.TimeZone;
import java.util.concurrent.ScheduledFuture;

@SpringBootApplication(exclude = MessageSourceAutoConfiguration.class)
@EnableScheduling
@RestController
public class Application extends SpringBootServletInitializer {

    @Autowired
    private DynamicCron dynamicCron;
    @Autowired
    private PropertyManager propertyManager;
    private static List<ScheduledFuture> scheduledFutures = new ArrayList<>();
    private static final Logger LOGGER = LoggerFactory.getLogger(Application.class);
    private static TaskScheduler scheduler;

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    private String cronConfig() {
        return propertyManager.getProperty("COMPANY", "JOB_NAME", "CRON_EXPRESSION");
    }

    @RequestMapping(value = {"scheduling/start"}, method = RequestMethod.GET)
    public @ResponseBody String startScheduling() {
        scheduleAll();

        LOGGER.info("Scheduling of jobs has been started.");
        return "Scheduling of jobs has been started.";
    }

    @RequestMapping(value = {"scheduling/cancel"}, method = RequestMethod.GET)
    public @ResponseBody String cancelScheduling() {
        cancelAll();

        LOGGER.info("Cancelling all scheduled jobs.");
        return "Cancelling all scheduled jobs.";
    }

    private void scheduleAll() {
        LOGGER.info("Scheduling all applications to run.");
        cancelAll();

        //eventually go through the database and load all jobs to be scheduled here.
        schedule(cronConfig());
    }

    /**
     * Cancel all the scheduled reports
     */
    private void cancelAll() {
        for (ScheduledFuture scheduledFuture : scheduledFutures) {
            scheduledFuture.cancel(true);
        }
        scheduledFutures.clear();
    }

    /**
     * Schedule the scheduled report with the given cron schedule information
     */
    private void schedule(String cronSchedule) {
        TimeZone tz = TimeZone.getDefault();
        LOGGER.info("Setting up application {} to execute with cron string: '{}'.", cronSchedule);
        CronTrigger trigger = new CronTrigger(cronSchedule, tz);

        scheduler = scheduler();
        if (scheduler == null) {
            LOGGER.error("Unable to schedule job as scheduler was not found");
            return;
        }

        ScheduledFuture<?> future = scheduler.schedule(new DynamicCron(), trigger);
        scheduledFutures.add(future);
    }

    @Bean
    public TaskScheduler scheduler() {
        if (scheduler == null) {
            ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler();
            scheduler.setPoolSize(10);
            scheduler.afterPropertiesSet();
        }
        return scheduler;
    }
}

This basically replicates the functionality the ScheduledTaskRegistrar provides allowing you manage the ScheduledFuture(s). Hopefully this can help someone else in the future.