Event handling

Use of @EventHandler annotation to push data into a SEP

Single event handler per class

The goal is to invoke a method on a user created node when an Event is posted to the encapsulating SEP.

The method must accept a single argument that is of type Event and be marked with @EventHandler annotation. There are no requirements on method naming, only the method signature and annotation are analysed by Fluxtion.

Fluxtion employs pattern type matching analysis to ensure the correct method dispatch occurs.

Example

The example is located here. A single event type MyEvent will be dispateched to an event handler method, MyEventProcessor.handleEvent

Node class

In this example MyEventProcessor handles MyEvent. The method is marked with the annotation @EventHandler to identify it as an event handler method to the Fluxtion compiler at generation time.

public class MyEventProcessor {
    
    @EventHandler
    public void handleEvent(MyEvent event){}
}

Generated SEP

Fluxtion ESC will generate the following SEP. The interface method onEvent discovers the runtime type (line 11) and dipatches the event to a type specific handleEvent method (line 20). The execution path is invoked in the handleEvent method.

public class SampleProcessor implements EventHandler, BatchHandler, Lifecycle {

  //Node declarations
  private final MyEventProcessor myEventProcessor_1 = new MyEventProcessor();

  public SampleProcessor() {}

  @Override
  public void onEvent(com.fluxtion.runtime.event.Event event) {
    switch (event.getClass().getName()) {
      case ("com.fluxtion.internal.fluxtionscratch.MyEvent"):
        {
          MyEvent typedEvent = (MyEvent) event;
          handleEvent(typedEvent);
          break;
        }
    }
  }

  public void handleEvent(MyEvent typedEvent) {
    //Default, no filter methods
    myEventProcessor_1.handleEvent(typedEvent);
    //event stack unwind callbacks
    afterEvent();
  }
  //content removed
}

Graph builder

The SEPConfig class that constructs the graph imperatively is shown below. Use of SEPConfig is described in imperative graph building.

public class Builder extends SEPConfig {

    @Override
    public void buildConfig() {
        MyEventProcessor  handler = new MyEventProcessor();
        addNode(handler);
    }

}