If you are using jrockit -
JAVA_VENDOR=Oracle
If you are using the normal/standard jdk -
JAVA_VENDOR=Sun
You can set JAVA_VENDOR explicitly in your startWebLogic.sh or setDomainEnv.sh file if you are having problems. You can also set the JAVA_VENDOR on the Server Start
tab in the admin console.
See these questions that more or less ask the same thing: