On Thu, 2002-09-12 at 12:45, Craig Longman wrote:
> On Thu, 2002-09-12 at 12:14, peter lin wrote:
> >
> >
> > You should know that JSP2.0 includes EL built in. the early access
> > implementation of JSP2.0 uses JSTL's el.
>
> oh, ok. well, that's good news. i guess that splits my question into a
> couple pieces:
>
> 1) jsp2.0 including EL, does that mean that the way one evaluates an EL
> parameter will change, or that explicit evaluation will no longer be
> necessary
If using JSP 2.0 EL machinery, then you will not have to perform
explicit evaluation in the tag library. The container will take care
of this at runtime.
> 2) is there a way of determining ( in a tag ) to determine what the JSP
> level container we're executing in. then the tag (during a phase-in
> period at least) could determine whether to explicitly evaluate it or
> not.
I think one approach is that if you don't want the container to evaluate
EL expressions, you can package the app using a Servlet 2.3 deployment
descriptor. JSP 2.0 containers will not perform EL evaluation in that
case. I also believe that if you use JSTL EL, and you want JSTL to
perform the EL evaluation you could also set a page property isELEnabled
to false and the container will not evaluate EL expressions.
I think there is a third option using a 2.4 deployment descriptor and
using a jsp-property-group to disable EL across a set of pages
identified by a URL pattern.
If you let the JSP 2.0 container evaluate the EL in a JSTL tag, then it
should be passed to JSTL as the evaluated value and you should have no
problems.
>
> and a third question i suppose:
> 3) is explicitly evaluating EL really as simple as calling
> ExpressionEvaluatorManager.evaluate() (as below), or is there some other
> prep/setup work i haven't noticed yet in the bowels of the current jstl
> package?
Will defer to someone more familiar with the EL machinery.
>
> > You may want to look at the draft spec to familiarize yourself with the
> > changes that will occur when JSP2.0 is released.
>
> i'll try and track it down, thanks.
>
> > peter lin
> >
> > Craig Longman wrote:
> > >
> > > hi there,
> > >
> > > i'm just starting out with jsp/taglibs, and have decided to focus on
> > > using the jstl as the basis for my efforts. it seems to provide exactly
> > > what i needed, some basic, compatible tags to get started.
> > >
> > > it is clear, however, that i'm going to have to write my own tags to get
> > > any serious work done.
> > >
> > > my question is this, i figure that if i'm going to standardize on the
> > > jstl, then it only makes sense to standardize on the EL stuff also, i
> > > prefer its style to the scriplet thingies, and its less typing. but,
> > > i'm wondering what the preferred/recommended method is for doing this.
> > >
> > > i see in the src dist for the reference jstl that there are a couple of
> > > classes that look promising to use. one is an interface
> > > (ExpressionEvaluator) and then an implementing class
> > > (ExpressionEvaluatorManager). using it appears to be as simple as this
> > > (from tag/el/core/ForEachTag.java):
> > >
> > > if( begin_ != null )
> > > {
> > > Object r = ExpressionEvaluatorManager.evaluate(
> > > "begin", begin_, Integer.class, this, pageContext );
> > > if (r == null)
> > > {
> > > throw new NullAttributeException("forEach", "begin");
> > > }
> > > begin = ((Integer) r).intValue();
> > > validateBegin();
> > > }
> > >
> > > it is acceptable to utilize this class in this manner for custom tags?
> > > or is there a better/standard way. i have been unable to find any docs
> > > that talk about using the standard EL in your own tags, but if anyone
> > > has any pointers, i would greatly appreciate it.
> > >
> > > thanks,
> > >
> > > --
> > >
> > > CraigL->Thx();
> > > Be Developer ID: 5852
> > >
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> CraigL->Thx();
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