Flex Data Services and Java JDKs
If you’re a newbie just starting on Flex Data Services 2.0 (FDS) and J2EE development, you will most likely go and download FDS from Adobe with the integrated JRun 4 application server immediately followed by a Java Development Kit (JDK) from Sun (if you don’t already have one).
And if you’re one to always have the latest and greatest or are just following the first link that you see on Sun’s webpage like any newbie would, you’ll probably grab a JDK targetting Java 1.5 and think that you can compile some of your own classes and go merrily along. Not quite so fast–you’ll actually need to tweak your JRun 4 installation if you plan on using the latest Java 1.5 JDK (it’s really pretty easy–see below the fold for more details). If, rather, you just want to get going right out of the box with the default installation, however, what you really want is the older Java 1.4.2 JDK.