How it works...

First, we are building a server to manage our event and observers:

public static void main(String[] args){
    try(SeContainer container =  
    SeContainerInitializer.newInstance().initialize()){
        container
            .getBeanManager()
            .fireEvent(new ExampleEvent("event: " 
            + System.currentTimeMillis()));
    }
}

This will give us all of the resources needed to run the recipe as if it were a Jakarta EE server.

Then, we build an observer, as follows:

public void thisEventBefore(
        @Observes @Priority(Interceptor.Priority.APPLICATION - 200) 
        MyEvent event){
  
    System.out.println("thisEventBefore: " + event.getValue());
}

So, we have three important topics:

• @Observes: This annotation is used to tell the server that it needs to watch the events fired with MyEvent.
• @Priority: This annotation informs in which priority order this observer needs to run; it receives an int parameter, and the execution order is ascendant.
• MyEvent event: This is the event being observed.

In the thisEventBefore method and thisEventAfter, we only changed the @Priority value and the server took care of running it in the right order.