I am getting the error below when I try to save the data.

object references an unsaved transient instance - save the transient instance before flushing:

I think the problem is beginning because of the commands below;

        @OneToMany
     public List<Item> getItemList() {
          if(itemList==null)
          {
          itemList= new ArrayList<Item>();          
               
          }


can you tell me how I can save the data