Your solution worked for me too. I found another solution using weblogic-application.xml
<?xml version="1.0" encoding="UTF-8"?>
With this file inside WEB-INF directory my application worked fine.
But the fact that the Hibernate depends on an older version of the antlr lib bother me. I have used 2.7.6 version, but Weblogic 11g already has a 2.7.7 version. That's the problem. Could it be a bug??