Adding a plug-in to a webapp

[Joe Bermann]

Hi,

I’m looking for some advice on how to design a Struts-based webapp that can 
accept dynamic plug-in components after deployment.  I’ve searched the 
archives and found some interesting posts about Struts Modules and Single 
Sign On, but I didn’t find anything that addressed my situation exactly.

I have a core webapp, let’s call it BaseApp, that contains a menu of launch 
points to various features.  After BaseApp is deployed and running at a 
customer site, the time will come when I want to add a launch point to a new 
feature there.  In my current design I’ll need to re-deploy an updated 
BaseApp that contains a new menu item and the new feature.  A much more 
flexible design would allow me “drop in” a new set of files that the BaseApp 
would recognize and link to (after restarting Tomcat).  This way the BaseApp 
wouldn’t have to be updated, re-qualified, or re-deployed (a huge savings at 
my company).

One of the problems is dealing with authorization issues – the users should 
have to log in only once and should be automatically logged out after a 
period of inactivity, regardless of where in the GUI they click.  
Unfortunately the BaseApp has already been developed with custom security 
code; container managed security was not used.  After the user’s password is 
authorized, a special object is stored in session scope; the presence of 
that object indicates an authorized user.

Another problem is upgrading the software in the field.  Eventually a new 
version of the BaseApp will be released and the deployment in the field 
needs to be upgraded.  This means that any plug-ins need to be upgraded too, 
or at least maintained (not wiped out).

I’ve thought of using separate webapps (i.e. the plug-in could be packaged 
as a new webapp) with a dynamic menu in the BaseApp, but then I’m faced with 
the authorization problems mentioned above.

Is there a standard pattern in Struts to satisfy these requirements (will 
Struts Modules do what I need)?  Is there some way to “drop in” additional 
files into a pre-deployed webapp?  Does anyone have experience with these 
types of issues?

Thanks!

-- Joe



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