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Apache speed: what variables are available in templates?

Is it possible to get a list of variables inside a template and fill them with a list? I would like my users to create their templates, which means I won't know what variables will be available?

EDIT:

In my template, users will decide what gets printed. For example,

$ users $ last

but from my application, I will not know what variables are used in the template. I would like to get a list like [users latest] that includes all the variables in the template so that I can populate them according to the custom specification.

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You might be able to collect the list by dropping the template and using the ReferenceInsertionEventHandler, which builds the list. The problem is that while templates have things like:

#if( $foo ) $bar #else $woogie #end

Your event handler will only see $ bar or $ woogie, not both.



This unsupported (and possibly deprecated) class might help:

http://svn.apache.org/viewvc/velocity/engine/branches/1.x/experimental/templatetool/

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I don't think there is an easy way to do this without overriding some of the speed classes.

Here are some options for how I would do it:



  • Add all the possible variables (I'm assuming there is a predefined set of them). If this is high performance look into caching.
  • Ask users what data they need before creating the template (if it's one time, just a form, if these variables don't change often write them in db).
  • Ask users to provide a list of the variables they need in some specific format inside the template for easy analysis of the rendering of the template, for example: <!--%%__VARS__%%users,latest%%__VARS__%%-->

  • Use regexp to locate the template file and find instances of $ var, which can be tricky.
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There are some discussions and ideas here for solving this problem. The preferred option is mainly to use a walker for the generated AST template. Not trivial.

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I found this one liner (save it as a snippet) in case you can't remember it.

## #foreach($key in $context.keys) <pre> $key</pre> #end

Hope it helps ...

Oh, remove ##

as it is commented

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