NHibernate一对多无法插入null键

Question

I'm trying to use NHibernate. I have these following tables:

    CREATE TABLE person(person_id INTEGER IDENTITY(1,1) NOT NULL,  
    person_first_name VARCHAR(55) NOT NULL,  
    person_last_name VARCHAR(55) NULL,   
    person_contacted_number INTEGER NOT NULL, 
    person_date_last_contacted DATETIME NOT NULL,
    person_date_added DATETIME NOT NULL,  
    CONSTRAINT PK_person PRIMARY KEY (person_id));

    CREATE TABLE person_order(order_id INTEGER IDENTITY(1,1) NOT NULL,  
    order_person_id INT NOT NULL,  
    CONSTRAINT PK_person PRIMARY KEY (order_id)),
    CONSTRAINT FK_person_order_person FOREIGN KEY(order_person_id)
    REFERENCES person (person_id);

Classes:

    public class Person
    {
        public virtual int person_id { get; set; }
        public virtual String person_first_name { get; set; }
        public virtual String person_last_name { get; set; }
        public virtual int person_contacted_number { get; set; }
        public virtual DateTime person_date_last_contacted { get; set; }
        public virtual DateTime person_date_added { get; set; }
        public virtual ISet<PersonOrder> person_orders { get; set; }
    }
    public class PersonOrder
    {
        public virtual int order_id { get; set; }
        public virtual int order_person_id { get; set; }
        public virtual Person Person { get; set; }
    }

hbm.xml:

  <class name="Person" table="`person`">
        <id name="person_id">
          <generator class="native"/>
        </id>
        <property name="person_first_name" />
        <property name="person_last_name" />
        <property name="person_contacted_number" />
        <property name="person_date_last_contacted" />
        <property name="person_date_added" type="LocalDateTime" />
        <set name="person_orders" table="`person_order`" cascade="all-delete-orphan" inverse="true">
          <key column="order_person_id"/>
          <one-to-many class="PersonOrder"/>
        </set>
  </class>

  <class name="PersonOrder" table="`person_order`">
     <id name="order_id">
      <generator class="native"/>
    </id>
    <many-to-one name="Person" column="order_person_id" cascade="save-update" />
  </class>

I want to save Person to database (cascade):

var newPerson = CreatePerson(); // return new Person
newPerson.person_orders = new HashedSet<PersonOrder> {new PersonOrder()};
session.Save(newPerson);

And have a error could not insert:

[TestConsoleApplication.PersonOrder][SQL: INSERT INTO [person_order] (order_person_id) VALUES (?); select SCOPE_IDENTITY()]

I think it's not correct one-to-many mapping for class. How to resolve this?

Answer 1

I would say, that the most suspected issue could be missing parent/Person setting on the Order itself.

Once we are not using cascading, NHibernate must know all the settings, independently. Other words, this is not enough *(simplified example, expecting IList instead of IEnumerable for person_orders)*:

var newPerson = CreatePerson(); // return new Person
newPerson.person_orders = new List<PersonOrder>();
// WRONG assignment
newPerson.person_orders.Add(new PersonOrder()); // first order
newPerson.person_orders.Add(new PersonOrder()); // second order

In this case, our new PersonOrder does not know about the Person , the reference. So we have to be sure, that it is assigned both ways (good practice anyhow):

// improve it
var order1 = new PersonOrder
{
    Person = newPerson,
};
var order2 = new PersonOrder
{
    Person = newPerson,
};
newPerson.person_orders.Add(order1); // first order
newPerson.person_orders.Add(order2); // second order

Once this is assured, then after session.Save(newPerson) and session save all orders ... the correct PersonId will be sent.

NOTE: Try to think about using the cascades, and marking the <set> with inverse="true" attribute. Honestly cannot remember scenario where not used this approach

EDIT: a bit different mapping I would suggest to change the mapping types. Instead of iesi ISet (which is really good if we need uniqueness) and the <set> , into standard IList<> and the bag mapping. Ie:

Hbm like this :

<bag name="person_orders" table="`person_order`" 
     cascade="all-delete-orphan" inverse="true">
      <key column="order_person_id"/>
      <one-to-many class="PersonOrder"/>
</bag>

the C# like this

public virtual IList person_orders { get; set; }

And the insertion code like this:

var newPerson = CreatePerson(); // return new Person
var order = new PersonOrder
{
    Person = newPerson,
};
newPerson.person_orders = new List<PersonOrder> {order};
session.Save(newPerson);

This will work (I am almost sure, because I just reproduced as similar as possible)