According to http://xstream.codehaus.org/faq.html, XStream supports jRockit from
version R.25 1.0

I'm running tomcat with jRockit R.27 and got hits warning when installing hudson :
Error

We detected that your JVM is not supported by Hudson. This is due to the
limitation is one of the libraries that Hudson uses, namely XStream. See this
FAQ for more details.
Detected JVM
Vendor : BEA Systems, Inc.
Version : R27.1.0-109-73164-1.5.0_08-20061129-1428-windows-ia32
VM Name : BEA JRockit(R)
OS Name : Windows XP