Implementing business logic

We may now outline the design of our system in the following diagram:

In this use case, the domain model will consist only of the Temperature class with the only double value inside. For simplicity purposes, it is also used as an event object, as shown in the following code:

final class Temperature {
   private final double value;
   // constructor & getter...
}

To simulate the sensor, let's implement the TemperatureSensor class and decorate it with a @Component annotation to register the Spring bean, as follows:

@Component
public class TemperatureSensor {
   private final ApplicationEventPublisher publisher;              // (1)
   private final Random rnd = new Random();                        // (2)
   private final ScheduledExecutorService executor =               // (3)
           Executors.newSingleThreadScheduledExecutor();

   public TemperatureSensor(ApplicationEventPublisher publisher) {
      this.publisher = publisher;
   }

   @PostConstruct
   public void startProcessing() {                                 // (4)
      this.executor.schedule(this::probe, 1, SECONDS);
   }

   private void probe() {                                          // (5)
      double temperature = 16 + rnd.nextGaussian() * 10;
      publisher.publishEvent(new Temperature(temperature));
      
      // schedule the next read after some random delay (0-5 seconds)
      executor
        .schedule(this::probe, rnd.nextInt(5000), MILLISECONDS);    // (5.1)
   }
}

So, our simulated temperature sensor only depends on the ApplicationEventPublisher class (1), provided by Spring Framework. This class makes it possible to publish events to the system. It is a requirement to have a random generator (2) to contrive temperatures with some random intervals. An event generation process happens in a separate ScheduledExecutorService (3), where each event's generation schedules the next round of an event's generation with a random delay (5.1). All that logic is defined in the probe() method (5).  In turn, the mentioned class has the startProcessing() method annotated with @PostConstruct (4), which is called by Spring Framework when the bean is ready and triggers the whole sequence of random temperature values.