import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface CronType {
    public String name();
}

////////////////////////////


/**
 * CronMaster service, loads all registered jobs on startup and exposes REST service.
 *
 * @author Alexander
 *
 */
@ApplicationPath("/cron")
public class CronMasterApplication extends Application {
    static Map<String,CronAgent> jobs = new HashMap<String, CronAgent>();

    public Set<Class<?>> getClasses() {
        return new HashSet<Class<?>>(Arrays.asList(CronMasterEndpoint.class));
    }

    static { //cool stuff, calls the method whenever this class is initialized
        registerJobs();
    }

    static void registerJobs() {
        final ClassLoader loader = Thread.currentThread().getContextClassLoader();
        try {
            ClassPath classpath = ClassPath.from(loader); // scans the class
                                                            // path used by
                                                            // classloader
            // all job classes have to be in the fi.observis.festivals.cron
            // package or subpackage of that
            for (ClassPath.ClassInfo classInfo : classpath.getTopLevelClassesRecursive("fi.observis.festival.cron")) {
                logger.info(classInfo.getSimpleName() + " <==> " + classInfo.getPackageName());
                /*
                 * Do annotation logic here.
                 */
                Class<?> currentClass = classInfo.load();//gets ur classes
                Annotation[] annotations = currentClass.getAnnotations(); //need to check if it has CronTask annotation
                logger.info("Annotations are: " + annotations.length);
                for (Annotation cur : annotations) {
                    if (cur.annotationType().equals(CronTask.class)) {
                        //Annotation is of type CronType
                        CronTask type = (CronTask) cur;

                        logger.info(cur.annotationType().getName());

                        //Put the job in our hashmap with the key of appid
                        @SuppressWarnings("unchecked")
                        Class<CronAgent> tempClass = (Class<CronAgent>) classInfo.load(); //generic class :D
                        jobs.put(type.name(), tempClass.newInstance()); //instantiate object from the generic class, and store to hash!
                        logger.info(type.name());
                    }
                }
            }

            //calling a job for example
            //jobs.get("aaltofestival").executeJob("aaltofestival");
        } catch (IOException | InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
        }

    }
}


///////////
package fi.observis.festival.cron.aaltofestival;

import *...
//using app id in the annotation for classes that extend the interface
@CronTask(name = "aaltofestival")
public class AaltoCronJob implements CronAgent {

    //interface method
    @Override
    public void executeJob(String appId) {
    }


}

//////////

public interface CronAgent {
    public void executeJob(String appId);
}