[jira] [Created] (VELOCITY-876) Support a Configurable EL within ${{...}} also $!{{...}} tags

["Terefang Verigorn (JIRA)" <ji...@apache.org>]

Terefang Verigorn created VELOCITY-876:
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             Summary: Support a Configurable EL within ${{...}} also $!{{...}} tags
                 Key: VELOCITY-876
                 URL: https://issues.apache.org/jira/browse/VELOCITY-876
             Project: Velocity
          Issue Type: Improvement
          Components: Engine
    Affects Versions: 1.7
            Reporter: Terefang Verigorn
            Priority: Minor
             Fix For: 2.x


Since Velocity2 is a Major version, why not start to support some new features?

As of Velocity 1.x you can use ${name} to refer to object "name" in the context, or use $!{name} if you want "" for null values.

How about using ${{ el-expression }} to evaluate and output the given "el-expression" in a configured el-engine with the current velocity context, same should hold for $!{{ el-expression }}.

Some possible engines would be :
commons-el, commons-jexl, ognl, mvel

if using el/jexl ${{name}} would be mostly the same as ${name}.

* usage cases

- the simple ${{...}} would allow more complicated expressions than present in the plain engine, especially if we look at the jexl2/3 features

- #if( ${{ }} ) -- would improve the boolean issue because the el could be used to wrap in "a?x:y"

* architecture

thru api abstraction, almost any el could be plugged in ( even groovy.eval )

core engine could ship with the api and el or jexl as the reference impl, other bindings would be optional jars with thier own deps.



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