使用 NHibernate Criteria API 选择特定的数据集和计数

Question

我为 NHibernate 的持久性设置了以下域：

我使用 PaperConfiguration 作为根聚合。

我想选择给定 Tier 和 AcademyYearConfiguration 的所有 PaperConfiguration 对象。根据以下示例，这非常有效：（

ICriteria criteria =
session.CreateCriteria<PaperConfiguration>()
    .Add(Restrictions.Eq("AcademicYearConfiguration", configuration))
    .CreateCriteria("Paper")
    .CreateCriteria("Unit")
    .CreateCriteria("Tier")
        .Add(Restrictions.Eq("Id", tier.Id))

return criteria.List<PaperConfiguration>();

不过也许有更好的方法来做到这一点）。

但还需要知道每个 PaperConfiguration 有多少 ReferenceMaterials，我想在同一个调用中获取它。避免 HQL - 我已经有一个 HQL 解决方案。

我知道这就是预测的目的，这个问题提出了一个想法，但我无法理解让它工作。

我有一个 PaperConfigurationView，而不是 IList; ReferenceMaterials ReferenceMaterialCount 并沿着思路思考

ICriteria criteria =
session.CreateCriteria<PaperConfiguration>()
    .Add(Restrictions.Eq("AcademicYearConfiguration", configuration))
    .CreateCriteria("Paper")
    .CreateCriteria("Unit")
    .CreateCriteria("Tier")
        .Add(Restrictions.Eq("Id", tier.Id))
    .SetProjection(
        Projections.ProjectionList()
           .Add(Projections.Property("IsSelected"), "IsSelected")
           .Add(Projections.Property("Paper"), "Paper")
            // and so on for all relevant properties
           .Add(Projections.Count("ReferenceMaterials"), "ReferenceMaterialCount")
    .SetResultTransformer(Transformers.AliasToBean<PaperConfigurationView>());

return criteria.List< PaperConfigurationView >();

不幸的是这不起作用。我做错了什么？

下面的简化查询：

ICriteria criteria =
session.CreateCriteria<PaperConfiguration>()
.CreateCriteria("ReferenceMaterials")
.SetProjection(
Projections.ProjectionList()
.Add(Projections.Property("Id"), "Id")
.Add(Projections.Count("ReferenceMaterials"), "ReferenceMaterialCount")
).SetResultTransformer(Transformers.AliasToBean<PaperConfigurationView>());
 return criteria.List< PaperConfigurationView >();

创建了这个相当意外的 SQL：

SELECT 
  this_.Id as y0_, 
  count(this_.Id) as y1_ 
FROM Domain.PaperConfiguration this_ 
  inner join Domain.ReferenceMaterial referencem1_ 
    on this_.Id=referencem1_.PaperConfigurationId

上面的查询失败并出现 ADO.NET 错误，因为它显然不是正确的 SQL，因为它缺少分组依据或计数为 count(referencem1_.Id) 而不是 (this_. ID）。

NHibernate 映射：

  <class name="PaperConfiguration" table="PaperConfiguration">
    <id name="Id" type="Int32">
      <column name="Id" sql-type="int" not-null="true" unique="true" index="PK_PaperConfiguration"/>
      <generator class="native" />
    </id>
    <!-- IPersistent -->
    <version name="VersionLock" />
    <!-- IAuditable -->
    <property name="WhenCreated" type="DateTime" />
    <property name="CreatedBy" type="String" length="50" />
    <property name="WhenChanged" type="DateTime" />
    <property name="ChangedBy" type="String" length="50" />

    <property name="IsEmeEnabled" type="boolean" not-null="true" />

    <property name="IsSelected" type="boolean" not-null="true" />

    <many-to-one name="Paper" column="PaperId" class="Paper" not-null="true" access="field.camelcase"/>

    <many-to-one name="AcademicYearConfiguration" column="AcademicYearConfigurationId" class="AcademicYearConfiguration" not-null="true" access="field.camelcase"/>

    <bag name="ReferenceMaterials" generic="true" cascade="delete" lazy="true" inverse="true">
      <key column="PaperConfigurationId" not-null="true" />
      <one-to-many class="ReferenceMaterial" />
    </bag>
  </class>

  <class name="ReferenceMaterial" table="ReferenceMaterial">
    <id name="Id" type="Int32">
      <column name="Id" sql-type="int" not-null="true" unique="true" index="PK_ReferenceMaterial"/>
      <generator class="native" />
    </id>
    <!-- IPersistent -->
    <version name="VersionLock" />
    <!-- IAuditable -->
    <property name="WhenCreated" type="DateTime" />
    <property name="CreatedBy" type="String" length="50" />
    <property name="WhenChanged" type="DateTime" />
    <property name="ChangedBy" type="String" length="50" />

    <property name="Name" type="String" not-null="true" />
    <property name="ContentFile" type="String" not-null="false" />
    <property name="Position" type="int" not-null="false" />
    <property name="CommentaryName" type="String" not-null="false" />
    <property name="CommentarySubjectTask" type="String" not-null="false" />
    <property name="CommentaryPointScore" type="String" not-null="false" />
    <property name="CommentaryContentFile" type="String" not-null="false" />

    <many-to-one name="PaperConfiguration" column="PaperConfigurationId" class="PaperConfiguration" not-null="true"/>
  </class>

Answer 1

您应该使用 Projections.GroupProperty() 而不是 Projections.Property()。