Spring: endpoint to start a scheduled task - spring-boot

Question

I have a scheduled task that works perfectly, like this:
#Scheduled(cron="*/5 * * * * MON-FRI")
public void doSomething() {
// something that should execute on weekdays only
}
I want to create a REST endpoint that would start this task out of it's normal schedule.
How would I programatically fire-and-forget this task?

Answer 1

You could do something really simple.
Your schedule:
#Component
#RequiredArgsConstructor
public class MySchedule {
private final MyClassThatHasTheProcessing process;
#Scheduled(cron = "*/5 * * * * MON-FRI")
public void doSomething() {
// the actual process is made by the method doHeavyProcessing
process.doHeavyProcessing();
}
}
Your Controller
#RestController
#RequestMapping(path = "/task")
#RequiredArgsConstructor
public class MyController {
private final MyClassThatHasTheProcessing process;
// the executor used to asynchronously execute the task
private final ExecutorService executor = Executors.newSingleThreadExecutor();
#PostMapping
public ResponseEntity<Object> handleRequestOfStartTask() {
// send the Runnable (implemented using lambda) for the ExecutorService to do the async execution
executor.execute(() - >{
process.doHeavyProcessing();
});
// the return happens before process.doHeavyProcessing() is completed.
return ResponseEntity.accepted().build();
}
}
This will keep your scheduled task working as well as being able do trigger the task on demand by hitting your endpoint.
The HTTP 202 Accepted will be returned and the actual thread released, while the ExecutorService will delegate the process.doHeavyProcessing execution to another thread, which means that it will run in a 'fire and forget' style, because the thread that is serving the request will return even before the other task is finally terminated.
If you don't know what is an ExecutorService, this may help.

Answer 2

This can be done by writing something like below
#Controller
MyController {
#Autowired
MyService myService;
#GetMapping(value = "/fire")
#ResponseStatus(HttpStatus.OK)
public String fire() {
myService.fire();
return "Done!!";
}
}
MyService {
#Async
#Scheduled(cron="*/5 * * * * MON-FRI")
public void fire(){
// your logic here
}
}