Do Jakarta/Tomcat "workers" fit in to this discussion?
"Since the JVM is multithreaded; the jni worker should be used only within multithreaded servers such as AOLServer.."
http://jakarta.apache.org/tomcat/tomcat-3.2-doc/Tomcat-Workers-HowTo.html
http://jakarta.apache.org/tomcat/connectors-doc-archive/jk2/jk/workershowto.html