What's the reason behind to include a engine in Java to run JavaScript?

Question

To let JavaScript able to run in server-side?

If it's justified, what's the advantage? and any good application for such use?

Answer 1

There are lots of possible reasons. Here's a blog post by Steve Yegge (of Google) explaining why he was looking into using Mozilla Rhino (which later because javax.script).

According to the Rhino site:

It is typically embedded into Java applications to provide scripting to end users.

So I guess that's one good reason. Other things I've read include doing it because you have some complex language that you want to run on either the browser or the server, and you don't want to write it twice (as here).

Generally speaking, that's a lot of complexity, and generally speaking, complexity is bad.