JavaFX Script isn't in JavaFX 2.0 - what's the practical impact for working with JavaFX now?

from my JavaOne talk.

At JavaOne, it was announced that JavaFX 2.0 won't support JavaFX Script. (Or at least, Oracle won't be updating the JavaFX Script compiler for JavaFX 2.0.) Although Oracle had kindly given partners and speakers a little advanced warning of this, I met quite a few people at JavaOne who were taken by surprise. And at face value, the situation today is a little odd:

• JavaFX 1.3.1 requires you to write in JavaFX Script
• JavaFX 2.0 won't let you write in JavaFX Script
• (and 2.0 isn't out until next year)

And many people find themselves in a dilemma: Does that mean all code for 1.3.1 has to be thrown away? What do you do until 2.0 is available if you can't just "wait a year" -- 2.0 code can't be written yet but 1.3.1 code would be wasted?

After rejigging my talk a little, I inserted a few slides on what I think the practical impact on our project is in the short term. After all, my team has a JavaFX 1.3.1 client. How has this announcement affected us?

Well, the first thing to say is that even today a lot of a JavaFX client can be written in Java. I ran some rough line counts on our JavaFX client -- the client I demo'ed at JavaOne -- and it came up as:

• 27% JavaFX Script
• 73% plain ol' Java

So the impact for us is a bit smaller than it appears. Part of that is because I was very cautious about committing the client to JavaFX. JavaFX 1.2, which we had to cope with until April 2010, had some very awkward bugs in it -- and there seemed to be a lot of risk with the Oracle buy-out and JavaFX gaining little market-share. So I kept as much of our code as possible in Java, ready to jump ship from JavaFX if we needed to. The libraries, model, data handling, and most of the guts of our code aren't written in JavaFX Script but just in Java. And it seems that's just as well. I realise other projects might not be in that situation though.

So this seems to be rule 1 for working with JavaFX at the moment:

If a class doesn't have to be written in JavaFX Script, write it in Java, Scala, Groovy or some other JVM language. Save yourself the effort of converting it later.

Various talks at JavaOne described possibilites for working in a JavaFX-Script-like way in JavaFX 2.0:

• Stephen Chin is keen to get an open source project going to update the JavaFX Script compiler so it can target 2.0
• Jonathan Giles and Stephen Chin showed how code in Scala, Groovy, or Clojure can look very similar indeed to JavaFX Script

In my view, it's too early to assess whether it will be easy to convert non-trivial JavaFX Script code to Scala or another JVM language. The 2.0 libraries are still being written, and nobody has much experience converting non-trivial apps yet -- even some of Oracle's demos in Richard Bair's JavaFX 2.0 talk were still written in JavaFX Script code; they hadn't been converted yet. It should be straightforward -- the 2.0 libraries are supposed to contain all the functionality of the existing JavaFX, so it should just be a matter of converting syntax, not redesigning your client. But let's wait and see on that.

It's also to early to assess whether the open source project to update the JavaFX Script compiler will be successful or not. Again, it should be. The JavaFX Script compiler always compiled to Java, and under 2.0 it'll have some libraries to target that will be a very close mapping to its language features.

So what can you do now?

• JavaFX 1.3.1 is a production release. And it works pretty well. (Unlike, say, 1.2!) So in the short term, targeting an app at 1.3.1 isn't so bad.
• JavaFX Script is still very fast for prototyping. Many of our visualisations were written in hours, not days. If you are doing prototyping or scientific experimentation where the results and the design decisions are more valuable than the code, JavaFX Script is still a pretty good choice.
• If you do keep most of your model code in Java, then the JavaFX Script code you write will usually be fairly simple. That means it's going to be less complicated to convert to another language if you decide to.

For my project, in fact, JavaFX Script not being supported in 2.0 makes very little difference. Government-funded research projects get fixed funding periods, and our current funding round finishes before 2.0 will be released. So we couldn't target 2.0 anyway. (If our hospital partners' experiments are successful, and more funding is won to take it further, that'd come with more development funding to deal with productisation issues -- including upgrading from 1.3.1 to 2.0. We'll make that as easy as possible to do, but we don't have to pencil it into the calendar yet.)