Java循环引用

Spring框架通过使用依赖注入解决了这个问题。简而言之，它的作用是实例化所有DAO，然后在实例化之后但在主要业务逻辑之前设置dao依赖关系。

如果您必须手动执行此操作，请参考以下示例：

public OrderService (){     orderDAO = DAOFactory.getDAOFactory().getOrderDAO();}public setItemService (ItemService service){     itemService = service;}public ItemService (){     itemDAO = DAOFactory.getDAOFactory().getItemDAO();}public setOrderService (OrderService service){     orderService = service;}...// instantiate singletonsorderService = new OrderService ();itemService = new ItemService ();// inject dependenciesorderService.setItemService (itemService);itemService.setOrderService (orderService);