1) What is the difference between
   a) session.save()
   b) session.saveOrUpdate()
   c) session.persist()

Ans : 
   a) session.save() : save() does an insert and will fail if the primary key is 
      already persistent. 
   b) session.saveOrUpdate() : 
      saveOrUpdate() does a select first to determine if it       
      needs to do an insert or an update. Insert data if primary key not exist 
      otherwise update data. 
   c) session.persist() : Does the same like session.save(). 
      But session.save() return Serializable object and session.persist() return 
      void. 
      session.save() returns the generated identifier (Serializable object) and 
      session.persist() doesn't.