Which JVM scripting language to use in order to customize a java web application?

Question

I'm designing a system and thinking about using some scripting language, in order to let a third party developer extend the capabilities of the system.

Just to give you an idea of my goal...When an event is triggered, the scripting language will need to invoke some Objects on the VM space that will provide common functionalities (e.g. storing objects on the BD, sending emails).

In a similar situation, a couple of years ago, I used BeanShell and it worked fine. Checking the website it looks like the project is a bit out of date.

Nowadays there are several VM languages, Groovy, Scala, just to name a few. What considerations should I have ? Do you have any experience in a similar environment?

first class support for libraries for timers, schedulers, http support and system calls should be the priority of choosing. but most language on JVM will have the support because they can reply on java libraries — Nagarjuna Pamu
– Nagarjuna Pamu, Commented Sep 1, 2016 at 12:45
And java 9 will come with a REPL too. Scala might be a too high goal. JavaScript is ugly (imho), but most accessible and one could use the Java Scripting API. — Joop Eggen
– Joop Eggen, Commented Sep 1, 2016 at 12:46
I highly recommend scala its worth the effort spent in learning. Scala already has REPL and Ammonite repl is also available which is way better than scala repl — Nagarjuna Pamu
– Nagarjuna Pamu, Commented Sep 1, 2016 at 12:48
I wouldn't call Scala a scripting language, any more than I would say Java is. — duffymo
– duffymo, Commented Sep 1, 2016 at 12:49

Will · Accepted Answer · 2016-09-01 13:01:58Z

3

Groovy is syntactically similar to C/Java language family, and, semantically, based on Ruby/Python/Smalltalk. It is supposed to have a smooth learning curve and shouldn't be hard to pickup and be productive right away (if that is a problem to your client).

It features GroovyShell and Eval, which are used to easily evaluate some script, stored in database, for example:

result = Eval.me """
    a = 1 + 2
    b = 3 + 4
    a + b
"""

assert result == 10

Note that this is too raw and you might need some kind of sandboxing, otherwise your client might do something nasty, like System.exit. For these scenarios, there are compiler customizers and groovy-sandbox. Also, you can add type checking through compiler customization.

answered Sep 1, 2016 at 13:01

Will

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1 Comment

Dani Cricco Over a year ago

Thanks for the recommendation. I think that you mentioned at least two key features: sandboxing, learning curve.

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