One reason, IBM Websphere. Currently the newest version of Websphere 6.0 is only handles 1.4.2. No idea when 7.0 is out and they’ll finally support it. Unfortunately the picture only gets worse from there. There’s no sightings of a 7.0 beta yet. Next you have a dependency on Rational Application Developer. Turns out RAD 6.0 is based on Eclipse 3.0 and won’t stop spitting errors at you if you dare to use generics or annotations.
Then there’s the nasty boat anchor for us. It turns out Portal Server is based on Websphere 5.1. After about 9 months at least now with Websphere 6.0 out they still haven’t ported it up to Websphere 6.0 even.
I think we’ll actually be able to use Java 1.5 features in maybe two years given the speed of Portal Server updates. The worst part is JBoss, Oracle, and BEA seem to have managed to get at least their main app servers up to the 1.5 JDK by now. You’d think the market leader would at least try to retain parity. The dolphin release of Java should be out by then so we can be two full releases behind at that point.