Modularity at JavaOne

Modularity had a lot of focus at last week's JavaOne conference. There were multiple references to JSRs 277 and 294 by Sun speakers, specific technical sessions on these JSRs, and a combined JSR 277 and 294 BOF.

There were a number of questions and comments at the JSR 294 session on the strawman's structuring of superpackage membership information in a separate source file rather than distributed across the source files of the member classes. This is something we should discuss on the mailing list (which you can read via the observer list).

Apart from an OSGi Best Practices technical session and the JSR 291 BOF, there were several mentions of OSGi and JSR 291 in other sessions. The goal of interoperating well with JSR 291 was presented in the JSR 277 session and even mentioned in one of Sun's general sessions¹. Stanley Ho will float a proposal on the JSR 277 mailing list in due course, so subscribe to the observer list if you are interested (Expert Group discussions should begin to be mirrored there soon).

Ethan Nicholas gave an update on the browser edition work to minimise the download and initial install size of the JRE. This seems to be making good progress, although it is not based on any of the above JSRs, so there may be some 'shake-out' in due course.

In one of the "meet the team" sessions, I asked Sun's class library team what their plan was for exploiting JSR 277 and JSR 294 in the JRE. It seems they don't yet have one. I expect this to change, particularly after the JSR 277 and JSR 294 prototypes become available in a subproject of OpenJDK.

In contrast, the Apache Harmony session described how OSGi had been used from the start to modularise the class libraries. I gave a demo. of prototype JVM support for modular Harmony in the JSR 291 BOF.

GlassFish v3 is developing a module system known as HK2 ("Hundred Kilobytes Kernel") which is loosely based on JSR 277. It also has a dependency injection framework similar to Guice. (Unlike GlassFish which is mostly licensed under the CDDL, HK2 currently has no license defined, so you may want to avoid looking at the source code until there is a proper license.)

I had face to face meetings with Andreas Sterbenz to discuss aspects of JSR 294 and with Stanley Ho and Michał Cierniak to discuss interoperation of JSR 277 with JSR 291. There's a lot of work ahead and we won't know for quite a while how good the interoperation with JSR 291 will really be, but everyone concerned seems to be well aware of the importance of this capability.

1. See a couple of minutes from Intro. and Technical Deep Dive starting at 18 minutes and 45 seconds from the start when Danny Coward talks about modularity and refers to the goal of interoperation with OSGi.