HQL关系映射

Question

我有一个层次模型，我正在尝试构建一个由业务与其相关中心（一对多）组成的集合。以下是我使用的HQL：

SELECT new map(b.businessName as name, c as centers) FROM Business b JOIN b.centers c GROUP BY c.centerID

我的期望结果是（以JSON为参考）：

[
  {"name": "Business 1",
   "centers": [ centerEntity1, centerEntity2, centerEntity... ]
  },
  {"name": "Business 2",
   "centers": [ centerEntity3, centerEntity4, centerEntity... ]
  }
]

然而，我的结果似乎更多地呈现一对一的关系：

[
  {"name": "Business 1",
   "centers": centerEntity1
  },
  {"name": "Business 2",
   "centers": centerEntity2
  }
]

此外，它正在运行1个查询以获取业务详细信息，然后进行其他查询以获取所有中心的信息。我认为这一切都可以使用JOIN FETCH组合成一个查询，但是会产生错误：

查询指定了联接获取，但被获取的关联的所有者不在选择列表中 [FromElement {explicit, not a collection join, fetch join, fetch non-lazy properties, classAlias = c, role = Business.centers, tableName = vw_hier_centers, tableAlias = centers1_, origin = vw_hier_businesses business0_，columns = {business0_.business_id, className = Center}}] [select new map(b.businessName as name, c as centers) FROM Business b JOIN FETCH b.centers c GROUP BY c.centerID]

- Tristan Lee

Answer 1

这个想法过于复杂了。下面是完全符合我需求的解决方案：

SELECT DISTINCT b FROM Business b JOIN FETCH b.centers

查询一次，可获取一个带有已获取中心的商家数组。

- Tristan Lee