We are upgrading oracle from 11g to 12c. My application is using hibernate3.jar which is 3.6.8-Final version. It works great with 11g using Oracle10gDialect but when I connect to 12c database I get below error. I also changed classes12.jar to ojdbc7.jar.

Invocation of init method failed; nested exception is org.hibernate.HibernateException: Unable to determine Dialect to use [name=Oracle, majorVersion=12]; user must register resolver or explicitly set 'hibernate.dialect'

I tried downgrading till 3.1.1 and upgrading till 3.6.10-Final. Below 3.6.8 my code wont compile as there is no Oracle10gDialect class before that. And even 3.6.10-final version gives me same above error. I cannot upgrade to Hibernate 4. Any advise will be of great help. thank you.

That's because Oracle12cDialect was added in Hibernate 4.