https://github.com/tolitius/on-demand-scheduler

Collection of Schedulable Tasks that can be scheduled on demand ( based on Spring Framework )
https://github.com/tolitius/on-demand-scheduler

Last synced: 6 months ago
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Collection of Schedulable Tasks that can be scheduled on demand ( based on Spring Framework )

• Host: GitHub
• URL: https://github.com/tolitius/on-demand-scheduler
• Owner: tolitius
• Created: 2010-09-21T20:29:09.000Z (about 15 years ago)
• Default Branch: master
• Last Pushed: 2015-08-28T02:15:59.000Z (about 10 years ago)
• Last Synced: 2025-04-02T08:23:15.899Z (7 months ago)
• Language: Java
• Homepage:
• Size: 120 KB
• Stars: 7
• Watchers: 4
• Forks: 4
• Open Issues: 0
• Metadata Files:
  • Readme: README.markdown

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README

          
## What is "On Demand Scheduler"? ##

Is a collection of self 'schedulable' tasks that are given a Spring's TaskScheduler will get scheduled on demand / programmatically.

## Why would I need it?##

Good question. Afterall, there is Spring's "<task:scheduled>", Quartz, JDK Timer, you name it...



The idea behind "On Demand" scheduler is to achieve three things:


1. Be very simple

2. Be based on Spring

3. Be able to be schedule tasks on demand


Currently, the way to schedule a task in Spring is to use <task:scheduled> ( satisfies #1 and #2 ):

    

        

    

    

Which means that the task is going to be scheduled _automatically_ when the application context is created.


"On Demand" scheduler compliments this ability with 'Schedulable' tasks that can be scheduled exactly _when needed_.

## Can you give me an example? ##

Business requirement: Whenever certain business service is done, schedule a pickup task ( e.g. to start picking up files every 5 seconds ).

    

        

        

        

        

        

    

That is pretty much it.



This will create an immutable task that can be injected anywhere and can be scheduled as:

    deliveryTask.schedule();

To fully satisfy the above business requirement, you would of course have an after / around advice applied to that "certain method" that needs attention ( e.g. businessService() ), and have this task injected into the aspect.

***

Another example: Start process all the shipments of Ubuntu DVDs to Apple Headquarters every 5 minutes while the store is closed e.g. from 21:00 to 08:00

    

        

        

        

            

                Ubuntu DVD

                

                    Apple Computer Inc 

                    1 Infinite Loop

                    Cupertino, CA 95014

            

        

    

Again, this is a simple Spring bean that can be injected anywhere, and the Spring's TaskScheduler APIs can be used. e.g. here is an example from "SchedulingRunnableTaskWithTriggerIntegrationTest":

    @Before

    public void shouldCreateTriggerAndScheduleTask() {

        long now = Calendar.getInstance().getTime().getTime();

        // Set a trigger to start in 5 second, run every 2 seconds for 15 seconds:

        Date startTime =  new Date( now + 5000 );

        Date endTime =  new Date( now + 15000 );

        long period = 2000;

        Trigger trigger = new DurationTrigger( startTime, endTime, period );

        taskScheduler.schedule( shipOrderTask, trigger );

    }

_where a "taskScheduler" is a regular Spring's "" and "org.gitpod.scheduler.trigger.DurationTrigger" is a custom trigger. You can simply grab it form sources._

## The gist of it

The main idea here is to have these simple tasks: FixDelayTask, TimeOutTask, RunnableTask, FixRateTask, CronTask, etc., some of which are suggested by Spring APIs ( e.g. take a look at Spring's ScheduledTaskRegistrar ), inject them in to components that need them as 'Schedulable's, and schedule whenever appropriate.

###### _TODO: more tasks, more tests, more love_