I found some transaction leaking in my application. That is a transaction starts, but not commit or rollback. Some of these cases happened when the application encountered errors or exception that not be caught. Is there any smart way that can protect my transaction not being leaking? Some way that not changes the application code, but my transaction class will be great.

My property setting is following:

<property name="hibernate.current_session_context_class">org.hibernate.context.ThreadLocalSessionContext</property>

Use automatic tx demarcation. Never issue a begin or a commit. The demarcation proxy will commit if the code threw no exception (you can even configure which exceptions should trigger a rollback or a commit anyway.).