You can not determine an object's "parent" - where was this object
created? - using any standard java methods. So unless you are able
to pass the "parent" as a reference in the constructor, I can't see
how it would be possible for your implentation classes to be able to
use the servlet's ServletContext interface.
If you find a workaround for this problem, I'd like to hear about it.
[ Matthias Carlsson ]
[ Programmer (Java, CGI/Perl, Javascript, HTML) ] [ Web Designer ]
[ E-Mail : [EMAIL PROTECTED] ] [ ICQ: 1430647 ]
[ http://home1.swipnet.se/~w-18931/programming/ ]
> -----Ursprungligt meddelande-----
> Fr�n: A mailing list for discussion about Sun Microsystem's Java Servlet
> API Technology. [mailto:[EMAIL PROTECTED]]F�r robert young
> Skickat: den 19 oktober 2000 22:13
> Till: [EMAIL PROTECTED]
> �mne: Re: ServletContext & newInstance
>
>
> unfortunately, that's just the problem. that's what i'd like to
> do, but the implementation classes are instantiated two levels down:
>
> TopServlet makes newInstance() of FirstClass which makes
> newInstance() of SecondClass which makes newInstance() of
> ImplementationClass
>
> all three of TopServlet, FirstClass, and SecondClass are "frozen" in
> the sense that if they are changed, it ripples through lots of
> implementation and worker classes, not just mine. not an option to
> modify the class interface.
>
> in particular, the implementation classes are created in classes which are
> not servlets, nor are their containing classes.
>
> it's in these implementation classes, which do all of the work one
> generally sees in servlets, that the ServletContext would be
> valuable. but the original designers, all gone to other bit buckets,
> chose to disengage the servlet classes from implementation ones. this is
> seen in the use of dynamic object creation. normally, this is a
> 'good thing'; i'm not so sure it is when dealing with servlets.
>
> what got me curious about the situation is that, from lexical scoping
> and address space points of view, a contained class is just
> like a method in a class, which can see and manipulate instance variables
> of its containing class. all of this stuff is contained in the
> address space of the originating servlet. the methods of a contained
> class can see the instance variables [a ServletContext instance, in
> this case] of everything 'above' it in the containment hierarchy.
> certainly, the symbol table is visible. put another way, i know
> who made me; i know the object in which i exist. and so on up the line.
> apparently, the java specification does not allow that visibility to be
> acted on; although i've not found any discussion of it, nor have i spent
> much time thinking about any negative implications. must be some.
>
> since i can trace my parentage, logically, the following is true:
>
> ImplementationClass.getCreator(getCreator(...)).getServletContext(
> ).getAttri
> bute("somethingCool")
>
> because it resolves to:
>
> TopServlet.getServletContext().getAttribute("somethingCool")
>
> if there were a getCreator method.
>
> robert young
>
> -----Original Message-----
> From: A mailing list for discussion about Sun Microsystem's Java Servlet
> API Technology. [mailto:[EMAIL PROTECTED]]On Behalf Of
> Matthias Carlsson
> Sent: Thursday, October 19, 2000 02:47 PM
> To: [EMAIL PROTECTED]
> Subject: SV: ServletContext & newInstance
>
>
> I've never tried what you explain, but can't you pass the servlet's
> ServletContext as a parameter when creating your worker (and implentation)
> classes?
>
> Like, set your worker classes to receive a ServletContext
> interface in it's
> constructor and then create the worker class inside the servlet by doing
> something like this:
>
> Worker worker = new Worker(this.getServletContext());
>
> [ Matthias Carlsson ]
> [ Programmer (Java, CGI/Perl, Javascript, HTML) ] [ Web Designer ]
> [ E-Mail : [EMAIL PROTECTED] ] [ ICQ: 1430647 ]
> [ http://home1.swipnet.se/~w-18931/programming/ ]
>
> > -----Ursprungligt meddelande-----
> > Fr�n: A mailing list for discussion about Sun Microsystem's Java Servlet
> > API Technology. [mailto:[EMAIL PROTECTED]]F�r robert young
> > Skickat: den 18 oktober 2000 17:37
> > Till: [EMAIL PROTECTED]
> > �mne: ServletContext & newInstance
> >
> >
> > the system with which i am working was designed such that
> > the servlets in the code base do little but instantiate
> > 'worker' classes. these are created dynamically using
> > newInstance(). then the actual implementation classes are
> > instantiated [with newInstance()] by these objects.
> >
> > it would be really useful to stuff stuff into the ServletContext,
> > from the implementation classes. ServletContext is, i think,
> > visible to the implementation classes at runtime, since they are
> > created in the scope of the originating servlet. or not?
> >
> > i've not found any syntax that will compile. is there any
> > way to reference the ServletContext in this scenario?
> >
> > thanx,
> > robert young
> >
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