In weblogic 10 server , if you run hibernate applications you will be annoyed to see this error
org.hibernate.QueryException: ClassNotFoundException: org.hibernate.hql.ast.HqlToken

the solution is to tell the server to use the antlr.jar in your lib directory instead of servers antlr.
You can do it by placing the antlr.jar in classpath.

add this to your startweblogic.cmd change path to wherever your antlr is
set PRE_CLASSPATH=C:\bea_portal\user_projects\w4WP_workspaces\poc1.0\poc2.0WAR\WebContent\WEB-INF\lib\antlr-2.7.5H3.jar;


and also add

set CLASSPATH=%PRE_CLASSPATH%;%SAVE_CLASSPATH%

You will be good to go