xalan parameter must be a "valid Java Object"

Keywords:
xalan IllegalArgumentException "The value of param" "must be a valid Java Object"

Problem:
On an application server (JBoss) where you can't control the version of xalan that is getting loaded with your web application, you get the following error in the preparation phase of a XML transform:

java.lang.IllegalArgumentException: The value of param [param-name] must be a valid Java Object
at org.apache.xalan.transformer.TransformerImpl.setParameter(TransformerImpl.java:1587)

Solution:
The issue here is that the object being set in the javax.xml.transform.Transformer.setParameter(String name, Object) is a null. In xalan 2.5.0 this doesn't seem to be an issue, but in xalan 2.7.0 it is!

Stop the null being put set as a parameter and the issue is solved.


Notes:
The last few posts have been around this issue of the web application not being able to control its classpath in JBoss. I've tried the ClassLoadingConfiguration advice in the JBoss Wiki with no success. The endorsed directory contains the different xalan library (as visible in the "sun.boot.class.path" system property) and despite specifying some sort of isolation, the endorsed directory still applies. As the issue was ultimately with a newer version of xalan and it's probably be bad to be putting nulls in anyway I haven't tried to force this class/library loading issue.