從兩個表JDO DataNucleus創建新對象

Question

我試圖通過使用DataNucleus持久化兩個類來創建DTO對象。

我希望創建的DTO：

@PersistenceAware
DtoObject{

   Protected String Id;  //populated by Order class
   Protected String status; //populated by Order class
   Protected String phoneNumber; //populated by Customer class
   Protected String address;  //populated by Customer class
}
The Objects:

 @PersistenceCapable
 @FetchGroup(name="dto", members = {@Persistent(name = "Id"), 
 @Persistent(name="status")})
 public Class Order{
   @PrimaryKey
   @Persistent
   private String Id;
   @Persistent
   private String status;
   @Persistent
   private Customer customer;
}

@PersistenceCapable
@FechGroup(name="dto", members = { @Persistent(name = "phoneNumber"),
@Peristent(name="address") })
public Class Customer{

   @PrimaryKey
   @Persistent
   private String Id;
   @Persistent
   private String phoneNumber;
   @Persistent
   private string Address;
}

JDODL：

Query q = pm.newQuery(Order.class);
            pm.getFetchPlan().setGroup("dto");
            q.setUnique(true);
            q.setFilter("Id == id");
            q.declareParameters("String id");
            q.setResultClass(DtoObject.class);
            DtoObject dto = (DtoObject)q.execute(id);

我可以使用映射到Order.class的屬性填充dto對象，但不能從Customer.class獲取屬性。 Data Nucleus加入表並從每個表中選擇適當的列，但保留phoneNumber = null和address = null；

有關如何通過一個查詢實現此功能的指針將不勝感激。

Answer 1

Query q = pm.newQuery("SELECT UNIQUE this.id, this.status, " + 
    " this.customer.phoneNumber, this.customer.address INTO " + 
    DtoObject.class.getName() + 
    " FROM " + Order.class.getName() + " WHERE this.id = :id");
DtoObject dto = (DtoObject)q.execute(idParam);

假設結果類（DtoObject）符合結果類的條件