James said that Sun won’t support any one of the scripting languages over the others because, “If we say Groovy is it, the Jython guys will come after us with knives.”1
So it looks like Sun are sitting back, waiting to see if any scripting language will become popular enough to be worth supporting, which is probably the wise thing to do at the moment.
Jython is mature and usable, but it’s development was on hiatus until recently. Jython’s only real problem is that it naturally appeals to only a small audience: programmers that know both Java and Python. Since Jython doesn’t have a Java-like syntax, Java programmers tend to dismiss it, and CPython programmers tend to avoid Jython because they need to learn Java and the Java libraries to get the benefit of running on the JVM. All that said, more and more Java developers are learning Python as Python’s industry mindshare grows. There is a chance that enough people will get excited about Python on the JVM to grow Jython into something big.
Groovy, on the other hand, is specifically aimed at Java developers, but it is not yet mature enough to use in most real-world situtations. Groovy has quite a number of challenges ahead, including defining the language and managing public expectations about the status of development. I think Groovy has a good chance of delivering a production quality implementation in the next 12 months. If they do, and the IDE vendors introduce Groovy support, then there is every chance that Groovy will be making its way into enterprises in the later half of 2006.
Personally, I hope both Groovy and Jython go on slug it out for developer mindshare over the next few years, but if I had to pick one over the other, I’d pick Groovy.
1 In truth, I can’t remember if it was “knives” or “an axe”. Gosling mentioned both kinds of weapons at different times. Anyway his point is well taken – those Jython advocates are dangerous :)