The AS7 book!

JBoss Tuning

Follow me on Twitter

Follow me
Top Programming Sites
Home Java EE 1.6 articles How to create an EJB Startup Service

How to create an EJB Startup Service

A startup service can be used to eagerly initialize some resources in your application or in external resources.
Thanks to Java EE 6 addition, you don't need anymore vendor solutions which allow to create startup classes.
Just plug in a Bean which is tagged as @Startup and @Singleton

@Startup
@Singleton
public class StartupBean {
  private String status;

  @PostConstruct
  void init {
    status = "Ready";
    // Here init your resources
  }
  ...
}

 

You can monitor the State of your Service by adding a simple property which can be accessed by your clients:

 

@Singleton 
@Startup 
public class StartupBean {
    public enum States {BEFORESTARTED, STARTED, PAUSED, SHUTTINGDOWN};
    private States state;
    @PostConstruct
    public void initialize() {
        state = States.BEFORESTARTED;
        // Perform intialization
        state = States.STARTED;
        System.out.println("Service Started");
    }
    @PreDestroy
    public void terminate() {
        state = States.SHUTTINGDOWN;
        // Perform termination
        System.out.println("Shut down in progress");
    }
    public States getState() {
        return state;
    }
    public void setState(States state) {
        this.state = state;
    }
}

 

Then your client will simply check the state property and verify what's the current state of the service

@EJB
StartupBean ejb;
 
System.out.println("State is "+ejb.getState());

Sometimes multiple singleton session beans are used to initialize data for an application and therefore must be initialized in a specific order. In these cases, use the javax.ejb.DependsOn annotation to declare the startup dependencies of the singleton session bean.

Here the PostStartupBean will be fired after the StartupBean is initialized:

@Startup
@Singleton
@DependsOn("StartupBean")
public class PostStartupBean {
 

  @PostConstruct
  void init {
 
    // Here init your resources
  }
  ...
}

How to create an EJB Startup Service
 

License

Mastertheboss.com Unless stated, all the contents of this site is licensed under Creative Comons License
Licenza Creative Commons