Why do so many insist on dragging the JVM into new applications?

Question

For example, I'm running into developers and architects who are scared to death of Rails apps, but love the idea of writing new Grails apps.

From what I've seen, there is a LOT of resource overhead that goes into using the JVM to support languages such as Groovy, JRuby and Jython instead of straight Ruby or Python.

Ruby and Python can both be interpreted on just about any OS, so I don't see any "write once run anywhere" advantage... why bring the hulking JVM along with you?

Answer 1

Java is a much, much more mature platform, with a lot of existing class libraries that could be "dropped in" and used, than, say, Ruby or Python (or even Perl, for that matter). So for people who like using existing code, rather than writing everything themselves, Java is a huge win.

For example, recently I've been looking for something like JAXB for Python or Ruby. In the end, I ended up using JRuby just because I haven't found any mature, widely-used XML-binding libraries.