如何在 NHibernate 中查询多对多对象

Question

我有两个具有多对多关系的数据库表：人员和组织。当然，还有一张表将这两者联系起来，称为 OrganizationPeople。

在 NHibernate 映射中，它们每个都有一个 Bag 的另一个。在 People 的映射中，Bag 是这样映射的：

  <bag name="Organizations" table="OrganizationPeople" cascade="none" inverse="false" lazy="true">
      <key column="PersonId"/>
      <many-to-many column="OrgId" class="DataTransfer.Organization, DataTransfer" fetch="select"/>
    </bag>

Organization 对 Bag 的映射就像

  <bag name="Persons" table="OrganizationPeople" cascade="none" inverse="false" lazy="true">
      <key column="OrgId"/>
      <many-to-many column="PersonId" class="DataTransfer.People, DataTransfer" fetch="select"/>
    </bag>

我现在要做的是通过 OrgId 查询组织以找出所有使用此 HQL 的相关人员：

 public IList<Organization> GetByOrgIdAndUserId(System.Guid orgId)
        {
            return NHibernateSession.CreateQuery("from Organization o join o.Persons as p where o.OrgId = :orgId")
                .SetGuid("orgId", orgId)
                .List<Organization>();


        }

这是我的单元测试返回的：

NHibernate: select organizati0_.OrgId as OrgId21_0_, people2_.PersonId as PersonId12_1_, organizati0_.EmployerIdentificationNo as Employer2_21_0_, organizati0_.InactiveDate as Inactive3_21_0_, organizati0_.OrgName as OrgName21_0_, organizati0_.UDSId as UDSId21_0_, organizati0_.ExternalOrgTypeCode as External6_21_0_, organizati0_.OrgInstance as OrgInsta7_21_0_, organizati0_.DUNS as DUNS21_0_, organizati0_.ProfileFileNumber as ProfileF9_21_0_, organizati0_.CentralRegistryEntityIdentificationNo as Central10_21_0_, organizati0_.PMSOrganizationFlag as PMSOrga11_21_0_, organizati0_.PIN as PIN21_0_, organizati0_.CreatedDate as Created13_21_0_, organizati0_.LastUpdateDate as LastUpd14_21_0_, organizati0_.InstitutionCode as Institu15_21_0_, organizati0_.WebURL as WebURL21_0_, people2_.FirstName as FirstName12_1_, people2_.LastName as LastName12_1_, people2_.Title as Title12_1_, people2_.UserId as UserId12_1_, people2_.GenderCode as GenderCode12_1_, people2_.EmployeeTypeCode as Employee7_12_1_, people2_.EmployeeStatusCode as Employee8_12_1_, people2_.PreferredContactMethodCode as Preferre9_12_1_ from IKNSubmissions.dbo.ExternalOrganizations organizati0_ inner join IKNSubmissions.dbo.OrganizationPeople persons1_ on organizati0_.OrgId=persons1_.OrgId inner join IKNSubmissions.dbo.People people2_ on persons1_.PersonId=people2_.PersonId where organizati0_.OrgId=@p0;@p0 = b7a8fda8-a65a-4607-81ca-e374fe75d685

System.ArgumentException: The value "System.Object[]" is not of type "IKN.DataTransfer.Organization" and cannot be used in this generic collection.
Parameter name: value
at System.ThrowHelper.ThrowWrongValueTypeArgumentException(Object value, Type targetType)
at System.Collections.Generic.List`1.VerifyValueType(Object value)
at System.Collections.Generic.List`1.System.Collections.IList.Add(Object item)
at NHibernate.Util.ArrayHelper.AddAll(IList to, IList from)
at NHibernate.Engine.Query.HQLQueryPlan.PerformList(QueryParameters queryParameters, ISessionImplementor session, IList results)
at NHibernate.Impl.SessionImpl.List(String query, QueryParameters queryParameters, IList results) 
NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available]
at NHibernate.Impl.SessionImpl.List(String query, QueryParameters queryParameters, IList results)
at NHibernate.Impl.SessionImpl.List<T>(String query, QueryParameters parameters)
at NHibernate.Impl.QueryImpl.List<T>()
at IKN.DataAccess.OrganizationDao.GetByOrgIdAndUserId(Guid orgId) in OrganizationDao.cs: line 16
at IKNDataAccessTest.OrganizationTest.CanGetByOrgId() in OrganizationTest.cs: line 42 

它似乎生成了基于映射更正的查询，但后来在创建返回结果时发生了一些事情。但我不确定是什么原因造成的。

非常感谢任何帮助。

约翰

Answer 1

试试这个：

 return NHibernateSession.CreateQuery("select o from Organization o join o.Persons as p where o.OrgId = :orgId")
   .SetGuid("orgId", orgId)
   .SetResultTransformer(new DistinctRootEntityResultTransformer())
   .List<Organization>();

Answer 2

我认为如果您删除联接，则关联的 People 对象的集合在您访问它们时将被延迟加载。如果您希望在同一个查询中加载集合，那么这应该可以：

select o from Organization o join fetch o.Persons as p where o.OrgId = :orgId