On Fri, 24 Jan 2003, Bueno Carlos M wrote:
> Date: Fri, 24 Jan 2003 16:18:49 -0500 > From: Bueno Carlos M <[EMAIL PROTECTED]> > Reply-To: Struts Users Mailing List <[EMAIL PROTECTED]> > To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]> > Subject: ActionMapping/ActionConfig cast in RequestProcessor.java > > Howdy -- > I have what is I guess a noob question, but I simply can't figure out these > seemingly important lines of code in RequestProcessor.java: > > > 646 ActionMapping mapping = (ActionMapping) > 647 moduleConfig.findActionConfig(path); > > > This appears on lines 646-7 in both 1.02 and 1.1. ActionMapping is a > *subclass* of ActionConfig, so how does this execute without throwing a > ClassCastException? I can cast an ActionMapping as an ActionConfig but not > the other way around. Yet, somehow, RequestProcessor seems to be doing just > that. Below is some sample code to illustrate my question. Can anyone shed > some light on this? It's too much majic for me. > It really is magic ... more so than I normally like to employ, but it was necessary for backwards compatibility. In Struts 1.0, the name of the JavaBean that stored stuff from an <action> element was ActionMapping -- and, this method was passed as an argument to every Action in the world. In Struts 1.1, we migrated the configuration objects to a new package (org.apache.struts.config), and gave them all names consistent with the element name that they represented (ActionConfig in this case). However, it wasn't a good idea to break everyone's existing Actions by changing the calling sequence, so ActionMapping is now a subclass of ActionConfig. The secret to making this work is that the objects stored (in ModuleConfig) for this collection really are ActionMappings and not just ActionConfigs -- so, when you pull them back out, the cast works. It also works for custom user subclasses, as long as the user extends ActionMapping and not ActionConfig. > -- Carlos Craig -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
