How to add new schedule job dynamically with Spring

Question

I am writing a Spring Boot App

My requirements are - In the resources (src/main/resources) folder if I add new xml files.. I should read those files and get some ur

Answer 1

If you want to dynamically schedule tasks you can do it without spring by using ExecutorService in particular ScheduledThreadPoolExecutor

Runnable task  = () -> doSomething();
ScheduledExecutorService executor = Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors());
// Schedule a task that will be executed in 120 sec
executor.schedule(task, 120, TimeUnit.SECONDS);

// Schedule a task that will be first run in 120 sec and each 120sec
// If an exception occurs then it's task executions are canceled.
executor.scheduleAtFixedRate(task, 120, 120, TimeUnit.SECONDS);

// Schedule a task that will be first run in 120 sec and each 120sec after the last execution
// If an exception occurs then it's task executions are canceled.
executor.scheduleWithFixedDelay(task, 120, 120, TimeUnit.SECONDS);

With spring you can rely on the Task and Scheduling API

public class MyBean {

    private final TaskScheduler executor;

    @Autowired
    public MyBean(TaskScheduler taskExecutor) {
        this.executor = taskExecutor;
    }

    public void scheduling(final Runnable task) {
        // Schedule a task to run once at the given date (here in 1minute)
        executor.schedule(task, Date.from(LocalDateTime.now().plusMinutes(1)
            .atZone(ZoneId.systemDefault()).toInstant()));

        // Schedule a task that will run as soon as possible and every 1000ms
        executor.scheduleAtFixedRate(task, 1000);

        // Schedule a task that will first run at the given date and every 1000ms
        executor.scheduleAtFixedRate(task, Date.from(LocalDateTime.now().plusMinutes(1)
            .atZone(ZoneId.systemDefault()).toInstant()), 1000);

        // Schedule a task that will run as soon as possible and every 1000ms after the previous completion
        executor.scheduleWithFixedDelay(task, 1000);

        // Schedule a task that will run as soon as possible and every 1000ms after the previous completion
        executor.scheduleWithFixedDelay(task, Date.from(LocalDateTime.now().plusMinutes(1)
            .atZone(ZoneId.systemDefault()).toInstant()), 1000);

        // Schedule a task with the given cron expression
        executor.schedule(task, new CronTrigger("*/5 * * * * MON-FRI"));
    }
}

And you can provide your own trigger by implementing Trigger

Don't forget to enable the scheduling by usin @EnableScheduling on configuration class.

About listening to directory content you can use WatchService. Something like:

final Path myDir = Paths.get("my/directory/i/want/to/monitor");
final WatchService watchService = FileSystems.getDefault().newWatchService();
// listen to create event in the directory
myDir.register(watchService, StandardWatchEventKinds.ENTRY_CREATE);
// Infinite loop don't forget to run this in a Thread
for(;;) {
   final WatchKey key = watchService.take();
   for (WatchEvent event : key.pollEvents()) {
       WatchEvent watchEvent = (WatchEvent) event;
       Path newFilePath = myDir.resolve(watchEvent.context());
       //do something with the newFilePath
    }
    // To keep receiving event
    key.reset();
}

Take a look at this article: Watching a Directory for Changes for more details.