not-null 属性 references a null or transient value - 对Inverse和Cascade的理解

Question

This is fragment of my database project, and this 是 Fluent NHibernate

自动生成的数据库片段

这些是我在上述数据库项目的 Fluent NHibernate 中的实体和映射类。

实体:

public class BaseEntity<T> where T : BaseEntity<T> {
    public virtual int Id { get; set; }
...
}

public class Person<T> : BaseEntity<T> where T : BaseEntity<T> {
    public virtual string FirstName { get; set; }
    public virtual string SecondName { get; set; }
    public virtual string LastName { get; set; }
    public virtual string PESEL { get; set; }
    public virtual DateTime BirthDate { get; set; }
    public virtual string City { get; set; }
    public virtual string PostalCode { get; set; }
    public virtual string Street { get; set; }
    public virtual string HouseNr { get; set; }
    public virtual string ApartmentNr { get; set; }
    public virtual string PhoneNr { get; set; }
    public virtual string Email { get; set; }
}

public class DrivingLicense : BaseEntity<DrivingLicense> {
    #region Relations
    public virtual IList<DrivingLicensePermissions> DrivingLicensePermissions { get; set; }
    public virtual Student Student { get; set; }
    #endregion

    public virtual DateTime IssueDate { get; set; }
    public virtual string DrivingLicenseNr { get; set; }
}

public class DrivingLicensePermissions : BaseEntity<DrivingLicensePermissions> {
    #region Relations
    public virtual DrivingLicense DrivingLicense { get; set; }
    #endregion

    public virtual DrivingLicenseCategory Category { get; set; }
}

映射:

class StudentMap : ClassMap<Student> {
    public StudentMap() {
        Id(x => x.Id);
        Map(x => x.FirstName).Not.Nullable().Length(25);
        Map(x => x.SecondName).Nullable().Length(25);
        Map(x => x.LastName).Not.Nullable().Length(50);
        Map(x => x.PESEL).Nullable().Length(11);
        Map(x => x.BirthDate).Not.Nullable();
        Map(x => x.City).Not.Nullable().Length(50);
        Map(x => x.PostalCode).Nullable().Length(6);
        Map(x => x.Street).Not.Nullable().Length(50);
        Map(x => x.HouseNr).Not.Nullable().Length(10);
        Map(x => x.ApartmentNr).Nullable().Length(10);
        Map(x => x.PhoneNr).Nullable().Length(20);
        Map(x => x.Email).Nullable().Length(100);

        References(x => x.DrivingLicense).Nullable().Cascade.All();
        References(x => x.User).Nullable().Cascade.All();
        HasMany(x => x.Participants).Cascade.All();
    }
}

class DrivingLicenseMap : ClassMap<DrivingLicense> {
    public DrivingLicenseMap() {
        Id(x => x.Id);
        Map(x => x.IssueDate).Not.Nullable();
        Map(x => x.DrivingLicenseNr).Not.Nullable().Length(20);

        HasMany(x => x.DrivingLicensePermissions).Cascade.All();
        References(x => x.Student).Not.Nullable();
    }
}

class DrivingLicensePermissionsMap : ClassMap<DrivingLicensePermissions> {
    public DrivingLicensePermissionsMap() {
        Id(x => x.Id);
        Map(x => x.Category).Not.Nullable();

        References(x => x.DrivingLicense).Not.Nullable();
    }
}

我的问题是这个异常：not-null 属性引用了空值或瞬态值 Model.Entities.DrivingLicense.Student, 当我试图像这样

坚持学生对象时

session.Save(student);

已将 DrivingLicense 对象分配给它的 DrivingLicense 属性。

我认为这是由于错误的映射引起的 - 错误的级联或缺少逆。我尝试了很多组合，但无法正常工作。 Student table 有 DrivingLicense_id 而相反，DrivingLicense 有 Student_id 列是否正确？！

Answer 1

这个问题的关键是 DrivingLicense 通过 Not.Nullable() 映射引用了 Student。这意味着当 NH 试图持久化 DrivingLicense 时，它是 Student 属性不能是 null.

调试代码并在 Save(student) 调用处暂停。检查对象图，查看 student 的 DrivingLicense 属性及其 Student 属性。我的猜测是 null.

您需要检查映射的 Not.Nullable() 方面或确保您的对象图正确 'wired'，然后再坚持。

Answer 2

为了解决我的问题，我不得不将 Reference-to-Reference 更改为 HasOne-to-Reference。

现在看起来像这样。

实体没有改变

映射:

class StudentMap : ClassMap<Student> {
    public StudentMap() {
        Id(x => x.Id);
        Map(x => x.FirstName).Not.Nullable().Length(25);
        Map(x => x.SecondName).Nullable().Length(25);
        Map(x => x.LastName).Not.Nullable().Length(50);
        Map(x => x.PESEL).Nullable().Length(11);
        Map(x => x.BirthDate).Not.Nullable();
        Map(x => x.City).Not.Nullable().Length(50);
        Map(x => x.PostalCode).Nullable().Length(6);
        Map(x => x.Street).Not.Nullable().Length(50);
        Map(x => x.HouseNr).Not.Nullable().Length(10);
        Map(x => x.ApartmentNr).Nullable().Length(10);
        Map(x => x.PhoneNr).Nullable().Length(20);
        Map(x => x.Email).Nullable().Length(100);

        HasOne(x => x.DrivingLicense).PropertyRef(x => x.Student).Cascade.All();
        References(x => x.User).Unique().Not.Nullable();
        HasMany(x => x.Participants).Cascade.All();
    }
}

class DrivingLicenseMap : ClassMap<DrivingLicense> {
    public DrivingLicenseMap() {
        Id(x => x.Id);
        Map(x => x.IssueDate).Not.Nullable();
        Map(x => x.DrivingLicenseNr).Not.Nullable().Length(20);

        HasMany(x => x.DrivingLicensePermissions).Cascade.All();
        References(x => x.Student).Unique().Not.Nullable();
    }
}

class DrivingLicensePermissionsMap : ClassMap<DrivingLicensePermissions> {
    public DrivingLicensePermissionsMap() {
        Id(x => x.Id);
        Map(x => x.Category).Not.Nullable();

        References(x => x.DrivingLicense).Nullable();
    }
}

感谢这一变化，循环引用消失了。 see it here

Students table 中没有 DrivingLicense_id，现在我可以像以前一样保存 Student 实体和 DrivingLicense，它是权限。

session.Save(student);

not-null 属性 references a null or transient value - 对Inverse和Cascade的理解

not-null property references a null or transient value - understanding of Inverse and Cascade

c#

nhibernate

fluent-nhibernate

fluent-nhibernate-mapping