net.kenblair.scheduler.service.Scheduler.java Source code

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Here is the source code for net.kenblair.scheduler.service.Scheduler.java

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/*
 * Copyright 2014 Ken Blair
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.kenblair.scheduler.service;

import net.kenblair.scheduler.entity.Schedulable;
import net.kenblair.scheduler.entity.ScheduledJob;
import net.kenblair.scheduler.repository.ScheduledJobRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.Lifecycle;
import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ScheduledFuture;

/**
 * A Spring based scheduler utilizing an injected {@link TaskScheduler} for executing {@link Schedulable} beans.
 * <p/>
 * Jobs are retrieved from an injected {@link ScheduledJobRepository} and scheduled according to their trigger.  A job
 * that is already scheduled but returns {@code false} from {@link ScheduledJob#equalTo(ScheduledJob)} will be
 * canceled and rescheduled.
 *
 * @author kblair
 */
@Service
public class Scheduler implements Runnable, ApplicationContextAware, Lifecycle {

    private final Logger logger = LoggerFactory.getLogger(this.getClass());
    private final ScheduledJobRepository repository;
    private final TaskScheduler taskScheduler;
    private final Map<String, Job> jobs;
    private ScheduledFuture schedulerTask;
    private ApplicationContext context;

    /**
     * Construct a new scheduler with the injected dependencies.
     *
     * @param repository    The repository.
     * @param taskScheduler The task scheduler.
     */
    @Autowired
    public Scheduler(final ScheduledJobRepository repository, final TaskScheduler taskScheduler) {
        this.repository = repository;
        this.taskScheduler = taskScheduler;
        this.jobs = new HashMap<>();
    }

    /**
     * Executes the scheduler.
     * <p/>
     * Should be run on a regular basis such as every 30 seconds.
     */
    public void run() {
        final Set<String> jobsToCancel = new HashSet<>(jobs.keySet());
        for (final ScheduledJob job : repository.findEnabledJobs()) {
            try {
                jobsToCancel.remove(job.getId());

                final String id = job.getId();

                if (jobs.containsKey(id)) {
                    if (!jobs.get(id).sameAs(job)) {
                        jobs.remove(id).cancel();
                    } else {
                        continue;
                    }
                }

                final Job theJob = new Job(getBean(job), job);
                jobs.put(id, theJob);
                theJob.schedule();
            } catch (final Throwable t) {
                logger.error("Exception while processing scheduled jobs", t);
            }
        }

        for (final String id : jobsToCancel) {
            jobs.remove(id).cancel();
        }
    }

    /**
     * A convenience method that will run the scheduled job exactly once.
     * <p/>
     * Note that this will build and configure a new bean.  If the job is already running it will execute separately
     * using the newly configured bean.  This is primarily useful for running disabled jobs or jobs that run on a sparse
     * schedule such as for testing.
     *
     * @param job The job to execute.
     */
    public void executeOnce(final ScheduledJob job) {
        final Schedulable bean = getBean(job);
        bean.run();
        bean.cancel();
    }

    /**
     * Build and configure a bean for the job.
     *
     * @param job The job.
     * @return The bean.
     */
    private Schedulable getBean(final ScheduledJob job) {
        final Schedulable bean = context.getBean(job.getBean(), Schedulable.class);
        bean.configure(job, job.getConfiguration());
        return bean;
    }

    /**
     * The application context to retrieve beans from.
     *
     * @param applicationContext The context.
     */
    @Override
    public void setApplicationContext(final ApplicationContext applicationContext) {
        this.context = applicationContext;
    }

    /**
     * Bootstraps the scheduler.
     */
    @Override
    public void start() {
        // TODO: make this configurable
        schedulerTask = taskScheduler.schedule(this, new CronTrigger("*/30 * * * * *"));
    }

    /**
     * Stops the scheduler gracefully.
     */
    @Override
    public void stop() {
        schedulerTask.cancel(true);
        for (final String id : new HashSet<>(jobs.keySet())) {
            jobs.remove(id).cancel();
        }
        schedulerTask = null;
    }

    /**
     * Returns {@code true} if the scheduler is currently running.
     *
     * @return True if running, false otherwise.
     */
    @Override
    public boolean isRunning() {
        return schedulerTask == null;
    }

    /**
     * Container for the bean, job and future.
     */
    class Job implements Runnable {

        private final Schedulable bean;
        private final ScheduledJob job;
        private ScheduledFuture future;

        private Job(final Schedulable bean, final ScheduledJob job) {
            this.bean = bean;
            this.job = job;
        }

        @Override
        public void run() {
            repository.updateLastRun(job.getId());
            bean.run();
        }

        public Job schedule() {
            future = taskScheduler.schedule(this, job.getTrigger());
            return this;
        }

        public Job cancel() {
            future.cancel(true);
            bean.cancel();
            return this;
        }

        public boolean sameAs(final ScheduledJob job) {
            return this.job.equalTo(job);
        }
    }
}