AdminApp
This page last changed on Jan 04, 2006 by phil.
TODO: Documenting updated version (currently at http://www.i-tao.com/adminapp.html). IN PROGRESS.
Introduction
This page aims at providing some additional information about the Hibernate AdminApp. The Hibernate
AdminApp (hereafter referred to as AA) was created by the Hibernate developers to show a possible
implementation strategy for Hibernate with Webwork. Although AA can still be used as a starting point for
webapplications, most of its libraries become quite aged (WW 2.0 beta, Hibernate 2, XWork 1.0 beta).
Therefore, a shiny new fork (AA2) has been created by Ron Chan.
AA2 relies on WW2.2, Hibernate 3.1, and Spring as its IoC container (rather than XWork's, which has
been deprecated in WW 2.2). We'll first discuss the original AA. Later on, we'll show the differences with
AA2. Ron, if you're reading this, feel free to point out any mistakes/edit this document.
Like we pointed out before, AA shows a possible implementation strategy to use Hibernate in WebWork in
combination with a so-called open-session-in-view pattern (more info, even more). This pattern allows
maximum flexibility in our view layer by creating a Hibernate Session object that will live till the end of
the request (after the view has been rendered). This allows lazy loading of objects in our view, rather
than having to preload all objects and their associations in our business layer, and yet ensures the correct
disposing of the Session object.
To accomplish this, AA uses XWork's components and interceptors:
• components: XWork manages the lifecycle of objects in several scopes (application, session,
request) and takes care of the IoC through the ..Aware interfaces (so called enablers). Hibernate's
expensive-to-create SessionFactory will thus be created in the application scope (meaning it will
only be initialised once when the application starts up), while the Session objects, used to load our
models, is registered in the request scope (will be created once per request).
• interceptors: AA uses an interceptor (the HibernateInterceptor) to extract the Session from the
WebWork action, so it can control the transactions, redirect/rollback on errors and properly dispose
the Session after the view is rendered.
AdminApp Source Overview
Now, let's properly dissect the AA files:
• /lib: contains the various jars for our application. Nothing special here.
• /src/java/org/hibernate/admin/action: lists our WebWork actions. All actions extend an abstract
AbstractAction file, which overrides the execute() method from our XWork's ActionSupport. This is
where we define a setHibernateSession() method, which is the method we declared in our enabler
interface (HibernateSessionAware). This will notify XWork to invoke its IoC magic to set the
HibernateSession.
Document generated by Confluence on Jul 21, 2007 05:37 Page 20
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