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https://issues.apache.org/jira/browse/VELOCITY-917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16856939#comment-16856939
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Claude Brisson commented on VELOCITY-917:
-----------------------------------------

The nature of the stub file is still not clear to me.

I think it's not difficult to parametrize the grammar file with 
${parser.char.whatever} maven properties, we don't need further Velocity 
templatization.

And Velocity can publish this grammar source file in its runtime resources. In 
this case, there's no other stub than the grammar source file itself.


> VTL Grammar Characters Configuration
> ------------------------------------
>
>                 Key: VELOCITY-917
>                 URL: https://issues.apache.org/jira/browse/VELOCITY-917
>             Project: Velocity
>          Issue Type: New Feature
>          Components: Engine
>    Affects Versions: 2.2
>            Reporter: Claude Brisson
>            Assignee: Claude Brisson
>            Priority: Major
>
> Experimental feature.
> The goal is to introduce new configuration parameters to be able to change 
> the VTL grammar. For instance:
> parser.character.dollar = '~'
> parser.character.hash = '@'
> parser.character.arobase = '%'
> parser.character.star = '?'
> Requirements:
> + fully B.C.
> + done at runtime, without the need to recompile the parser
> + null impact on performance
> Implementation:
> 1. Parametrize code that needs explicit references to those characters
> 2. Define a ParserTokenManager interface and have the parser use this 
> interface rather than a concrete class
> 3. Use a custom class loader to *patch* the concrete token manager .class 
> file, instantiate this custom token manager and initialize parsers with it
> The binary patch is prepared at compilation time (there will be one patch per 
> JRE vendor and class file version).
> Due to the limited capability of this technique, the chosen characters are 
> restricted to UTF-8 single bytes characters. Patches _could_ be prepared for 
> two-bytes or more characters, but there would be the need to have as many 
> parser objects as variants in one/two/... characters combinations.
> Also, some characters and combinations are obviously invalid.



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