Spring dm Server Considered Cool?

w-jax is over...

I'm just returning from w-jax 2009, one of the biggest german Java conferences, covering every technology related to Java actually.

If there are any hypes this year, they are these: Scala, Cloud Computing and OSGi. And, of course, Spring – which is all around.

Spring Source employs a lot of brave guys, and hearing first-hand about their newest coolest technologies is always refreshing. Did you know that Tomcat is to a large extent pushed by guys paid by Spring Source? I forgot the exact number, but Eberhard Wolff said the majority of bug fixes and commits is done by Spring Source's Tomcat team.

Spring dm Server is Cool!

There have been some sessions about Spring dm Server, and when taking a closer look it seems to be clear why Spring Source invests in Tomcat that much. Spring dm server is based on Tomcat, and they add the ability to deploy web application modules as OSGi bundles. This way, you can partition your web apps into separate bundles to deploy them independantly and dynamically into the server. Yes, they are preserving OSGi's dynamic, meaning that you can stop, start or refresh a particular bundle without the need to stop and restart the server. As you would expect, other bundles continue to work. If a requested OSGi service is temporarily not available, dm Server will wait 5 minutes for it being redeployed.

Spring dm server is part of Spring Tool Suite, an Eclipse based development environment which is also able to auto-deploy a module whenever it changes.

All of this is quite gorgeous from a technical perspective, and the Spring guys had to cope with some really hard issues (for instance, realted to JPA where they need an application wide visiblity of bundles as well as load time weaving – you won't want to know the details...).

Really? What for?

But... is this really of any interest in the field?

Our customers are using WebSphere (or WebLogic or maybe JBoss) application server, and all of them are not capable of running such a modularized, OSGi based application. Moreover, in a production environment, there is no need and most often it is actually not even desired to be able to refresh application bundles dynamically.

So, what's left? Modularizing your application? Right, that is leading to a better structure and less coupling and blah blah, but the same can be achieved without OSGi (just let the business domain drive your application "slices"). It's just that you are forced to use modules (bundles) when you are using OSGi.

If at all, Spring dm server will pay off for developers since it may speed up development (especially the build-deploy-test cycle). But is this really, I mean really, hurting us that much? Hence, if you were asking me, a lot of technical overhead and server lock-in for no real benefit.

So, will Spring dm server be able to gain real attention, I mean beyond being technically cool? I'm sceptical. As always, time will tell...