Question

I’m building a JSF+Facelets web app, one piece of which is a method that scans a directory every so often and indexes any changes. This method is part of a bean which is in application scope. I have built a subclass of TimerTask to call the method every X milliseconds. My problem is getting the bean initialized. I can reference the bean on a page, and when I go to the page, the bean is initialized, and works as directed; what I would like instead is for the bean to be initialized when the web context is initialized, so that it doesn’t require a page visit to start the indexing method. Google has shown a few people that want this functionality, but no real solutions outside of integrating with Spring, which I really don’t want to do just to get this piece of functionality.

I’ve tried playing around with both the servlets that have ‘load-on-startup’ set, and a ServletContextListener to get things going, and haven’t been able to get the set up right, either because there isn’t a FacesContext available, or because I can’t reference the bean from the JSF environment.

Is there any way to get a JSF bean initialized on web app startup?

Answer 1

If your code calls FacesContext, it will not work outside a thread associated with a JSF request lifecycle. A FacesContext object is created for every request and disposed at the end of the request. The reason you can fetch it via a static call is because it is set to a ThreadLocal at the start of the request. The lifecycle of a FacesContext bears no relation to that of a ServletContext.

Maybe this isn’t enough (it sounds like you’ve already been down this route), but you should be able to use a ServletContextListener to do what you want. Just make sure that any calls to the FacesContext are kept in the JSP’s request thread.

web.xml:

<listener>     <listener-class>appobj.MyApplicationContextListener</listener-class> </listener> 

Implementation:

public class MyApplicationContextListener implements ServletContextListener {      private static final String FOO = 'foo';      public void contextInitialized(ServletContextEvent event) {         MyObject myObject = new MyObject();         event.getServletContext().setAttribute(FOO, myObject);     }      public void contextDestroyed(ServletContextEvent event) {         MyObject myObject = (MyObject) event.getServletContext().getAttribute(                 FOO);         try {             event.getServletContext().removeAttribute(FOO);         } finally {             myObject.dispose();         }     }  } 

You can address this object via the JSF application scope (or just directly if no other variable exists with the same name):

<f:view>     <h:outputText value='#{applicationScope.foo.value}' />     <h:outputText value='#{foo.value}' /> </f:view> 

If you wish to retrieve the object in a JSF managed bean, you can get it from the ExternalContext:

FacesContext.getCurrentInstance()             .getExternalContext().getApplicationMap().get('foo');