In my case I m using EntityManager, and I have to update collection type attribute in entities throuph the parent object:

@MappedSuperClass
abstract class Entity{
   private String uid;
   @Transiant
   private String typeCode = getClass().getSimpleName();

   public void setAttribute(string attributeName, Object value){
      //setting the attribute value wit reflection
   }

   public boolean isNew(){
      // whether the Object is persisted or not yet 
   }

   public <T> T get(String attributeName){
      //generic getter for all attributes with reflection
   }

}

class Order extends Entity{
   //other attributes
   @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "order")
   private List<OrderEntry> orderEntries = new ArrayList<>();
}

class OrderEntry extends Entity{
   @ManyToOne(fetch = FetchType.EAGER)
   private Order order;
}

when I do something like :

order = entityService.get("Order", uid);
newEntries = order.get("entries");
newEntries.removeAt(1);
order.setAttribute("entries", newEntries);
entityService.save(order);

the collection in that object is not updated. but updating another attribute works fine.

the save method I need it that way so it has to work for all entities:

@Transactional
public <T extends Entity> void save(T entity){
   if(entity.isNew()){
      entityManager.persist(entity)
   }else{
      entityManager.merge(entity)
   }
}