David Graham said:
> --- "Craig R. McClanahan" <[EMAIL PROTECTED]> wrote:
> >
> >
> > On Wed, 16 Jul 2003, Ranjangaonkar, Vaibhav (HQP) wrote:
> >
> > > Date: Wed, 16 Jul 2003 12:56:09 -0700
> > > From: "Ranjangaonkar, Vaibhav (HQP)" <[EMAIL PROTECTED]>
> > > Reply-To: Struts Developers List <[EMAIL PROTECTED]>
> > > To: Struts Developers List <[EMAIL PROTECTED]>
> > > Subject: RE: DynaActionForm.getMap() change
> > >
> > > My 0.2 cents -
> > > I think, idea to provide getMap() method is great !
> > > Yes, to solve the performance problem, I think, then
> > > We will have to keep track when underlying map has
> > > Changed. Then, create unmodifiable map only if it changed
> > > Since the last time...
> > >
> >
> > The current implementation already has getMap() -- the problem is that
> > it
> > returns the real HashMap that is internally used to store property
> > values,
> > which exposes those values to being modified by means other than through
> > the DynaActionForm methods.
> >
> > I don't like the performance impact of creating a new wrapper instance
> > on
> > every call to getMap(), however -- that can happen lots of times in a
> > page. It's probably possible to create the wrapper once and then cache
> > it
> > (to reduce the impact somewhat), but it is still a spurious object
> > creation.
>
> I considered caching as well but thought the implementation might get a
> bit ugly. It also doesn't help the form.map.prop issue.
>
> >
> > > Actually, this is a common java idiom, I think. Whenever
> > > We need to expose a collection from a class, we should
> > > return unmodifiable variant of it so that encapsulation
> > > doesn't break, but then, we have performance issue, as
> > > David said...
> > >
> > > Thanks.
> >
> > The reason to think about doing it is usability, which sometimes needs
> > to
> > win out over O-O purity :-).
>
> I often argue from the OO purist perspective (if you hadn't guessed by now
> :-). However, sometimes that's just playing devil's advocate. I think
> the usability issue here probably justifies DynaActionForm implementing
> Map. Is there any other way of acheiving form.prop for a DynaActionForm?
i don't know about JSTL-EL, but Velocity users would only need a get(String
key) method to have ${form.prop} work for us. and i think this will make
several of us happy too! :)
Nathan Bubna
[EMAIL PROTECTED]
> If we do implement Map we should note in the reasons in the javadoc so
> it's less confusing for extenders/customizers.
>
> David
>
> >
> > All of the Struts tags, because they use commons-beanutils under the
> > covers, treat DynaBean beans and standard JavaBeans identically -- the
> > internal implementation knows exactly what to do. So you can say things
> > like:
> >
> > <html:bean:write name="customer" property="firstName"/>
> >
> > Now, assume you've got a page author that wants to switch and use JSTL
> > EL
> > expressions instead. Their natural first inclination is going to be to
> > write:
> >
> > <c:out value="${customer.firstName}"/>
> >
> > which will work fine for a standard JavaBean, but not fine for a
> > DynaBean.
> > If it *happens* to be a DynaActionForm, you can work around this by
> > saying:
> >
> > <c:out value="${customer.map.firstName}"/>
> >
> > because we added getMap() to DynaActionForm. This is really confusing
> > to
> > newcomers, and would be unnecessary if we went to DynaActionForm
> > implementing Map. Then, the user's initial guess at how to write the
> > expression would have been correct.
> >
> > Given that JSP 2.0 makes EL expressions available everywhere in a page,
> > so
> > that you'd be able to write just this instead:
> >
> > ${customer.firstName}
> >
> > then I think the usability issue is strong enough that we should look at
> > making DynaActionForm implement Map so that it plays nicely with all EL
> > expressions.
> >
> > SIDE NOTE: In JavaServer Faces, the APIs let you customize a thing
> > called
> > the PropertyResolver, which is the piece of code that interprets the "."
> > or "[]" operators in an EL expression. In the most recent release of
> > the
> > Struts-Faces integration library, I took of advantage of this and
> > implemented support for DynaBeans -- but that only works for value
> > reference expressions in Faces components, not in other uses of EL in
> > the
> > page.
> >
> > Craig
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: [EMAIL PROTECTED]
> > For additional commands, e-mail: [EMAIL PROTECTED]
> >
>
>
> __________________________________
> Do you Yahoo!?
> SBC Yahoo! DSL - Now only $29.95 per month!
> http://sbc.yahoo.com
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [EMAIL PROTECTED]
> For additional commands, e-mail: [EMAIL PROTECTED]
>
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
