Want a JVM with just the pieces you need?

Stop me if you've heard this before: the JRE is too big to be a casual, on-demand download, so end users won't install it. If true, one solution is to download just enough of a JRE to bootstrap an application and then get just the pieces the user needs right then.

If this is a familiar argument to you, then you're probably a long-time reader of Ethan Nicholas' blog, as he has been calling for some time for a "Java Browser Edition" that would do just this.

Well, now Ethan is at Sun. And this proposal for an incrementally-downloaded JRE is happening. And he gets to do it... if it's even possible at all. In "Java Browser Edition": New name, first steps, he writes:

I was cautioned by several folks at Sun that the Browser Edition would simply never happen. It would never be approved as a feature in the first place, and even if it were approved, we would never be able to actually pull it off. I'm told that this basic idea has actually been attempted within Sun twice before, and in both cases the resulting size reduction wasn't enough to be worthwhile. The core VM, it seems, is simply too big, and trying to make it smaller is too hard. There has even been a detailed analysis of the idea which paints a rather bleak picture of the potential gains.

But under the new name "Java Kernel", Ethan's trying to make this a reality. In his blog, you'll find his interesting approach for developing a runtime that is just enough to do a System.out.println(), or bring up an AWT Frame.

His approach to determining what classes are necessary seems similar to the Java Media Framework's JMF Customizer, which allowed you to create a JAR of only those classes your JMF application needed. Maybe there are some insights from that project that could be brought to bear on this effort?

At any rate, the small, modular JRE has long been a dream of many Java developers. After all, if the network is the computer, why not get Java in a just-in-time piecemeal fashion, over the network?