Re: Problem with variable evaluation in Velocity 1.2

[Petr Toman <Pe...@pinknet.cz>]

> This works as long you want to WRITE the output, but becomes useless if
> what you want is to resolve to an object reference...Been through that

Exactly.

> public Object referenceEval( Context, Reader ) throws Exception

Would be handy, indeed. Anyway, is there any workaround for my example?

Thanks,
Petr
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Re: Problem with variable evaluation in Velocity 1.2

[Petr Toman <Pe...@pinknet.cz>]

> >> public Object referenceEval( Context, Reader ) throws Exception
> >
> > Would be handy, indeed. Anyway, is there any workaround for my example?
>
> I hunted this problem down, as I felt bad for you waiting so long :)
>
> The problem is that between 1.1 and 1.2, we made the internal Velocity
> engine singleton free, and the result is that there is no living
> introspector available (it was a singleton), so that's why ASTMethod
> coughs the hairball.

Thanks a lot! Got it working now. Btw, how can I detect Velocity version? Of
course, I can Class.forName("org.apache.velocity.runtime.RuntimeInstance")
in this case, but it would be useful to have it done in some standard way...

> So...  You can hack a solution, but this is a gory hack, IS NOT SUPPORTED,
> AND CAN'T BE GUARANTEED TO WORK TOMORROW, NEXT WEEK, OR EVER :)

Umm, perhaps a silly question: how to recognize the *supported* API? :) How
about dividing javadocs into public/internal APIs (would make it also more
readible)?

Bye, Petr
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Re: Problem with variable evaluation in Velocity 1.2

["Geir Magnusson Jr." <ge...@optonline.net>]

On 1/2/02 1:24 PM, "Petr Toman" <Pe...@pinknet.cz> wrote:

>> This works as long you want to WRITE the output, but becomes useless if
>> what you want is to resolve to an object reference...Been through that
> 
> Exactly.
> 
>> public Object referenceEval( Context, Reader ) throws Exception
> 
> Would be handy, indeed. Anyway, is there any workaround for my example?
> 

Well, yes, sort of.

I hunted this problem down, as I felt bad for you waiting so long :)

The problem is that between 1.1 and 1.2, we made the internal Velocity
engine singleton free, and the result is that there is no living
introspector available (it was a singleton), so that's why ASTMethod coughs
the hairball.

So...  You can hack a solution, but this is a gory hack, IS NOT SUPPORTED,
AND CAN'T BE GUARANTEED TO WORK TOMORROW, NEXT WEEK, OR EVER :)

This will get you going.  Create a RuntimeInstance, init() it, and then use
it when init-ing the node tree.  Modulo import statments
    
        RuntimeInstance ri = new RuntimeInstance();
        ri.init();

        String definition = "$var1.trim().length()";

        // init parser
        Parser parser = new Parser(new VelocityCharStream(new
            StringReader(definition), 0, 0));
        SimpleNode node = (SimpleNode) parser.process().jjtGetChild(0);

        System.out.println( node );

        // init context
        InternalContextAdapterImpl context = new
            InternalContextAdapterImpl(new VelocityContext());
        node.init(context, ri);

        // evaluate
        context.put("var1", new String(" 123456 "));
        System.err.println("1st value = >" + node.execute(null, context) +
"<");

        context.put("var1", new String(" 123 "));
        System.err.println("2nd value = >" + node.execute(null, context) +
"<");


This will get you going again.

I'll fix things so that you can't init the tree with null for the
RuntimeServices...

This is effectively a bug report, so thanks!  :)

Geir


-- 
Geir Magnusson Jr.                                     geirm@optonline.net
System and Software Consulting
"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." - Benjamin Franklin



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