Perform action when JAX-RS/Java EE application is starting

Question

Is there some way to check when a JAX-RS/Java EE application is starting/deployed?

At these moment, I'd like to check whether a database is initialized. Otherwise, only if the database is not initialized, I need to initialize it, and I need to check it when the Java EE application starts.

So, I need to know if there is any way to catch when a JAX-RS/Java EE application starts.

Any ideas?

Answer 1

There are at least three ways to achieve it:

Using ServletContextListener from the Servlet API

Since JAX-RS is built on the top of the Servlet API, the following piece of code will do the trick:

@WebListener
public class StartupListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent event) {
        // Perform action during application's startup
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        // Perform action during application's shutdown
    }
}

Using @ApplicationScoped and @Observes from CDI

When using JAX-RS with CDI, you can have the following:

@ApplicationScoped
public class StartupListener {

    public void init(@Observes 
                     @Initialized(ApplicationScoped.class) ServletContext context) {
        // Perform action during application's startup
    }

    public void destroy(@Observes 
                        @Destroyed(ApplicationScoped.class) ServletContext context) {
        // Perform action during application's shutdown
    }
}

Please note you must use @ApplicationScoped from the javax.enterprise.context package and not @ApplicationScoped from the javax.faces.bean package.

Using @Startup and @Singleton from EJB

When using JAX-RS with EJB, you can try:

@Startup
@Singleton
public class StartupListener {

    @PostConstruct
    public void init() {
        // Perform action during application's startup
    }

    @PreDestroy
    public void destroy() {
        // Perform action during application's shutdown
    }
}