In your mapping file, ScreenTb class has a one-to-many relation with AccessTb class. But in the SClient.java, you are trying to save string objects in the set instead of
When you save screenTB, hibernate also will try to save accessTbs colleaction (cascade effect). But it will fail because , the collection contains Strings instead of our mapped entities (AcccessTb). Try to add AccessTB objects to the set and see.