THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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As I write this, we don't have documentation on how to create more script engines, but that's not too hard to do if you take one of the simple existing engines as an example.
The JRuby engine for example, implemented in the scripting/ruby module, is built out of two simple classes, one that inherits from AbstractSlingScriptEngine, and one that inherits from AbstractScriptEngineFactory. The code is very simple, it's basically only a wrapper around the JRuby engine, that adapts it for Sling.
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The javascript engine provides wrappers to make it easier to access JCR and Sling objects from server-side javascript, and also uses a clever EspReader (sorry it's not that ESP) to convert .esp scripts to plain javascript code.
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