Spring Transactions and hibernate.current_session_context_class
Solution 1:
When using spring and spring managed transactions never mess around with the hibernate.current_session_context_class property UNLESS you are using JTA.
Spring will by default set its own CurrentSessionContext implementation (the SpringSessionContext), however if you set it yourself this will not be the case. Basically breaking proper transaction integration.
The only reason for changing this setting is whenever you want to use JTA managed transactions, then you have to setup this to properly integrate with JTA.