Executing task after deployment of Java EE application

Question

I have a Java EE application which should start a synchronization process with an external system once after its deployment.

How could I implement this requirement?

Answer 1

Below are listed a couple of popular methods for getting lifecycle callbacks in JavaEE apps.

Create a javax.servlet.ServletContextListener implementation

If you have a web component to your .ear file (embedded .war) or your deployment is a .war by itself you can add a ServletContextListener to your web.xml and get a callback when the server starts or is shutting down.

Example:

package com.stackoverflow.question

import javax.servlet.ServletContextListener;
import javax.servlet.ServletContextEvent;

public class MyServletContextListener implements ServletContextListener{

   @Override
   public void contextInitialized(ServletContextEvent contextEvent) {
        /* Do Startup stuff. */
   }

   @Override
   public void contextDestroyed(ServletContextEvent contextEvent) {
        /* Do Shutdown stuff. */
   }

}

and then add this configuration to your web.xml deployment descriptor.
$WAR_ROOT/WEB-INF/web.xml.

    
      com.stackoverflow.question.MyServletContextListener
    

Create an EJB 3.1 @Startup Bean

This method uses an EJB 3.1 singleton to get a startup and shutdown callback from the server.

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.ejb.Startup;
import javax.ejb.Singleton;

@Singleton
@Startup
public class LifecycleBean {

  @PostConstruct
  public void init() {
    /* Startup stuff here. */
  }

  @PreDestroy
  public void destroy() {
    /* Shutdown stuff here */
  }

}