This approach sounds similar to the Spring IoC framework.
Objects are defined in an xml file and a manager loads them
into memory. Your action class looks up beans using something
like:

MyBD bd = (MyBD)applicationContext.getBean("MyBD");

So you don't have to implement the ServiceLocator or
Singleton patterns. 

It provides declarative transaction services as well.

Check it out here:
http://www.springframework.org/

robert

> -----Original Message-----
> From: HG [mailto:[EMAIL PROTECTED]
> Sent: Thursday, July 22, 2004 5:22 AM
> To: Struts Users Mailing List
> Subject: Re: About Struts + JBoss preference issue
> 
> 
> Hi Marco
> 
> > I have  questions coz I m interested in that approach..
> 
> I am happy that you find it interesting :-)
> 
> > I assume u have a config file for telling the PlugIn Mgr what
> > To load, correct?
> 
> The plugins, names and classed that implement the plugin interface are
> stored in a table in a database.
> When the pluginmanager initializes, it performs a query on the database,
> fetching the plugins to load.
> 
> Then the PluginManager iterates the found plugin and performs this sequence
> in each interation
> 
> - Load the class (implementing the plugin interface) and get an instance of
> it.
> - initialize the plugin (performing lookup of remote home through
> ServiceLocator and creating remote object (Facade) to associate with the
> plugin.
> 
> But it could easily be a XML file, or anything else
> 
> > U use the PlugInMgr as singleton, correct? Coz right now I m following
> > Similar 'approach' but I m storing the BD in the ServletContext, and
> > what
> > I don't like much is that every time I have to retrieve it, I have to
> > Do a cast....
> 
> The plugin manager is stored in ServletContext, and I have a base class
> (PluginManagerAction) for my action, which have a method with the following
> signature
> 
> public PluginManager getPluginManager();
> 
> In my action which derives from PluginManagerAction I do this:
> 
> MyPluginInterface plugin = (MyPluginInterface)
> getPluginManager().getPlugin("myplugin");
> 
> I have to type cast the interface because getPluginManager() return the
> superclass interface Plugin
> 
> No I am ready to invoke methods of the plugin.
> 
> What is it you don't like, when doing type casts...?
> 
> Regards
> 
> Henrik
> 
> 
> 
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