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From "Bob Schellink (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CLK-306) Replacing OGNL with MVEL
Date Thu, 05 Apr 2012 06:11:32 GMT

    [ https://issues.apache.org/jira/browse/CLK-306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13247054#comment-13247054
] 

Bob Schellink commented on CLK-306:
-----------------------------------

Yep that would make the test pass, however the test is about ensuring that the binding occurs
on private variables. OGNL supports this feature, MVEL does not which is why we cannot simply
replace OGNL with MVEL as it could break existing applications.
                
> Replacing OGNL with MVEL
> ------------------------
>
>                 Key: CLK-306
>                 URL: https://issues.apache.org/jira/browse/CLK-306
>             Project: Click
>          Issue Type: New Feature
>          Components: core
>    Affects Versions: 1.4
>         Environment: Target Click 1.5
>            Reporter: Bob Schellink
>            Assignee: Bob Schellink
>             Fix For: 2.3.1
>
>         Attachments: expression-language-performance.rar, expression-language-performance.zip,
mvel.zip
>
>
> I have been following both OGNL and MVEL (another expression language) development the
last couple of months. If we are going to make changes to this here are some things you might
find interesting:
> * OGNL 2.7.1 which is included in tapestry 4.1, now sports byte code enhancement. This
was added by one of the tapestry authors to make OGNL much faster than its reflection mode.
However in my testing 2.7.1 threw exceptions every now and then. So still buggy.
> * MVEL (http://mvel.codehaus.org/) seems like a good replacement for OGNL. It has good
docs and is actively developed. They even fixed a bug I logged! Like OGNL, MVEL also runs
in two modes, either reflection or byte compiled. Unlike OGNL, MVEL's reflection mode is faster
than Click's reflection mode.
> I am no expert on this but according to the article below (from MVEL's author), byte
code enhancement have some problems in that generated classes accumulate in java's perm space
and will only be removed when their classloader is removed.
> http://artexpressive.blogspot.com/2007/07/mvel-by-numbers-real-story.html
> So MVEL in reflection mode looks like an ideal solution here. The power of OGNL with
the performance of Click reflection.
> Table columns can again take advantage of expressions. For example to aggregate a total
for the row -> new Column("price * tax");

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