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From "Andrew Fink (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CLK-306) Replacing OGNL with MVEL
Date Sat, 25 Feb 2012 05:21:46 GMT

    [ https://issues.apache.org/jira/browse/CLK-306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13216316#comment-13216316
] 

Andrew Fink commented on CLK-306:
---------------------------------

Malcolm Edgar wrote:
I think there are a couple of options here:
1. Rollback the changes to use OGNL,
2. Replace OGNL with MVEL, and stop supporting access to private variables (could break a
fair bit of code)
3. Have a pluggable PropertyService with OGNL and MVEL implementations (what should be the
default?)

Of these options I would prefer #3.
===

Pluggable PropertyService is very good idea! One can implement then Spring's SpEL implementation
too.

                
> 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
>
>
> 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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