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From "Najeed Ahmed Khan" <nak...@interwoven.com>
Subject javax.el.ELContext.getFunctionMapper().resolveFunction() returns null always
Date Fri, 13 Feb 2009 07:01:52 GMT
Hi,

 

I'm developing an application to parse EL scripts in a file and evaluate
them. I am using Java Unified EL for the same. The value expressions are
resolving fine however the functions are not. I'm using Tomcat 6.0.10
which is bundled with JBoss 4.2.3.

 

The way I am evaluating the expression is:

 

final MethodExpression methodExpr =

 
exprFactory.createMethodExpression(jspContext.getELContext(), el,
expectedType, paramTypes);

Object result = methodExpr.invoke(jspContext.getELContext(), params);

 

However, the function is not being invoked and I get a stack trace like
such:

2009-02-12 22:35:13,629 [http-0.0.0.0-8080-5] ERROR STDERR () -
javax.el.ELException: Function 'testtld:escapeJava' not found

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.lang.ExpressionBuilder.visit(ExpressionBuilder.java:171)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.parser.SimpleNode.accept(SimpleNode.java:129)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.lang.ExpressionBuilder.prepare(ExpressionBuilder.java:133)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.lang.ExpressionBuilder.build(ExpressionBuilder.java:147)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.lang.ExpressionBuilder.createMethodExpression(ExpressionBu
ilder.java:197)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
org.apache.el.ExpressionFactoryImpl.createMethodExpression(ExpressionFac
toryImpl.java:57)

2009-02-12 22:35:13,630 [http-0.0.0.0-8080-5] ERROR STDERR () -     at
test.util.ELExpressionEvaluator.evaluate(ELExpressionEvaluator.java:120)

 

The jsp page that I am using to obtain the ELContext has the taglib
directive to include that particular tld. If I invoke that JSP function
from a JSP page(using EL), it works fine. However, when I try to resolve
the function programmatically as above, I get the error.

 

When I checked the Tomcat source code, I noticed in
org.apache.jasper.el.ELContextImpl :

 

private final static FunctionMapper NullFunctionMapper = new
FunctionMapper() {

        public Method resolveFunction(String prefix, String localName) {

            return null;

        }

    };

 

 

And a few lines below that,

 

private FunctionMapper functionMapper = NullFunctionMapper; // immutable

 

Although there is a 
 
    public void setFunctionMapper(FunctionMapper functionMapper) {
        this.functionMapper = functionMapper;
    }

 

I am not sure whether that is invoked or how to have it invoked.

 

This could be the problem for me as the
ELContext.getFunctionMapper().resolveFunction(...) would return null and
I receive a message which corresponds to the Method object resolving to
null. 

 

I searched over the internet and did not come up with anything
related/conclusive that could point me towards a configuration or
programmatic step that I could've missed.

 

I'd appreciate it if you could give me some pointers as to what might be
the problem here and how to fix it. Also, I do not understand why the
org.apache.jasper.el package is being used instead of the org.apache.el
package which is the newer implementation.

 

Thanks,

Najeed.

 


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