API for expression language evaluation

2003-08-20 Thread Johann Uhrmann 
Hello,

is there an API for expression language evaluation?

E.g. it should be able to evaluate the following attribute values:

${bean.property}
  Should be evaluated to the property value of the bean.
${empty collection}
  should be evaluated to true/false
foobar
  should become the string foobar.
Does the JSTL provide such an API?

Thank You,

Hans

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Re: API for expression language evaluation

2003-08-20 Thread Felipe Leme 
On Wednesday 20 August 2003 06:19 am, Johann Uhrmann wrote:

 is there an API for expression language evaluation?

Yes, there is. But it's part of Jakarta Standard, not JSTL itself.

 ${bean.property}
Should be evaluated to the property value of the bean.

Take a look on this article, it explain how to achieve that:

http://www.onjava.com/pub/a/onjava/2002/10/30/jstl3.html


 Does the JSTL provide such an API?

Unfortunately, the JSTL 1.0 specification doesn't provide that API. But that's 
not really a problem because:

- most - if not all - of current JSTL 1.0 implementations are based on Jakarta 
Standard - which provides such API
- JSTL 1.1 (and I guess the next versions too) requires JSP 2.0, which takes 
care of EL handling

Felipe



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Re: API for expression language evaluation

2003-08-20 Thread Sgarlata Matt 
Yes, there is.  For an example on how to add the EL to your own tags you 
can look at the struts-el tag libraries which are included as part of 
the Struts core.  I use the org.apache.strutsel.taglib.utils.EvalHelper 
class to evaluate EL expressions.  This ties my application to Struts, 
but I am comfortable with that.  If you are not, it should be simple to 
tie your classes only to the JSTL by only referencing the 
org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager 
class, which the EvalHelper depends on.

Matt

Johann Uhrmann wrote:

Hello,

is there an API for expression language evaluation?

E.g. it should be able to evaluate the following attribute values:

${bean.property}
  Should be evaluated to the property value of the bean.
${empty collection}
  should be evaluated to true/false
foobar
  should become the string foobar.
Does the JSTL provide such an API?

Thank You,

Hans

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Matthew Sgarlata
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Booz Allen Hamilton Inc.
Work: 703-377-0871
Fax: 703-902-3608
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