Java EE Enterprise Application: perform some actio

问题:

This question already has an answer here:

• Using special auto start servlet to initialize on startup and share application data 1 answer

I would like to perform some action as soon as my application (Enterprise Application with Business Logic, EJB, and a Client, Web) is deployed. For example I would like to make some entity in a persistent state, or otherwise create a file. How can I do that?

Thanks.

回答1:

Configure SerlvetContextListener and override contextInitilized()

in your web application description , web.xml

<web-app ...>
    <listener>
        <listener-class>com.someCompany.AppNameServletContextListener</listener-class>
    </listener>
</web-app

---

package com.someCompany;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class AppNameServletContextListener implements ServletContextListener{

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
        System.out.println("ServletContextListener destroyed");
    }

    @Override
    public void contextInitialized(ServletContextEvent arg0) {
        System.out.println("ServletContextListener started");   
                // do the things here 
    }
}

回答2:

The "default" way is to have a servlet with an init() method. Then in the servlet-descriptor you mark this servlet as load-on-startup 1:

Example:

<servlet-name>Seam Resource Servlet</servlet-name>
   <servlet-class>org.jboss.seam.servlet.SeamResourceServlet</servlet-class>
   <load-on-startup>1</load-on-startup>
</servlet>

As soon as the servlet is deployed (which happens after the EJBs are deployed), that init() method is called and you can execute the task you want.

回答3:

With present web application in your ear, the easiest and simplest would be to use ServletContextListener, otherwise in EJB 3.1 you could use automatic timers or startup singleton session beans.