Q: Java 1.5 Issues
We are still working against Java 1.4, and will continue to always support it. But many users are upgrading to 1.5, as it can lead to some nice speed increases. Some users have reported problems with the defaults on GeoServer 1.3 with Java 1.5. As of 1.3.0-RC6 this should be fixed (by adding an extra 1.8 megs to your download, sorry!).
The most common error due to Java 1.5 is:
javax.xml.transform.TransformerFactoryConfigurationError: Provider org.apache.xalan.processor.TransformerFactoryImpl could not be instantiated: java.lang.NullPointerException
To fix this, downloaded XALAN-J binaries and move the xalan.jar file to [tomcat]/common/endorsed if you're running tomcat or $GEOSERVER_HOME/server/geoserver/WEB-INF/lib if running the binary install. This is due to Java 1.5 not including the xalan interpretive processor, while 1.4 does. For the 1.3.0 release we will likely just include that jar, since 1.5 is becoming the standard.
note: xalan 2.7.0 has additional dependencies! xml-apis.jar, xercesImpl.jar, and serializer.jar should be copied to the same location as xalan.jar