Hello,
I have a simple relational schema with two tables :
[code]
mysql> describe customers;
+-------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | text | YES | | NULL | |
+-------+---------+------+-----+---------+----------------+
2 rows in set (0.03 sec)
mysql> describe invoices;
+-------------+---------------+------+-----+---------+----------------
+
| Field | Type | Null | Key | Default | Extra
|
+-------------+---------------+------+-----+---------+----------------
+
| id | int(11) | NO | PRI | NULL | auto_increment
|
| date | datetime | YES | | NULL |
|
| amount | decimal(10,0) | YES | | NULL |
|
| customer_id | int(11) | NO | MUL | NULL |
|
+-------------+---------------+------+-----+---------+----------------
+
4 rows in set (0.02 sec)
[/code]
And a simple object model :
[code]
using System;
using System.Collections.Generic;
namespace CRM
{
public class Customer
{
public virtual int Id
{
get;
set;
}
public virtual string Name
{
get;
set;
}
public virtual IList<Invoice> Invoices
{
get;
set;
}
}
public class Invoice
{
public virtual int Id
{
get;
set;
}
public virtual DateTime Date
{
get;
set;
}
public virtual decimal Amount
{
get;
set;
}
}
}
[/code]
I'd like to create a one-to-many relationship between "Customer" and
"Invoice" to be able to navigate by using the "Customer.Invoices"
property.
So I've tried the following mapping :
[code]
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="Business"
namespace="CRM">
<class name="Customer" table="customers">
<id name="Id" column="id">
<generator class="native" />
</id>
<property name="Name" column="name" />
<bag name="Invoices" cascade="all">
<key column="customer_id" />
<one-to-many class="Invoice" />
</bag>
</class>
<class name="Invoice" table="invoices">
<id name="Id" column="id">
<generator class="native" />
</id>
<property name="Date" column="date" />
<property name="Amount" column="amount" />
</class>
</hibernate-mapping>
[/code]
But this code :
[code]
using System; // Console
using System.Collections.Generic; // IList<>, Dictionary<,>
using System.Linq; // ToList()
using NHibernate; // ISessionFactory, ISession, ITransaction
using NHibernate.Criterion;
using NHibernate.Cfg; // Configuration
using CRM; // Customer, Invoice
namespace TestNHibernate
{
class Program
{
static void Main(string[] args)
{
try
{
Configuration configuration = new Configuration();
configuration.AddProperties
(
new Dictionary<string, string>
{
{ "dialect",
"NHibernate.Dialect.MySQLDialect" }
}
);
configuration.AddFile("CRM.hbm.xml");
configuration.Configure();
ISessionFactory sessionFactory =
configuration.BuildSessionFactory();
ISession session = sessionFactory.OpenSession();
ITransaction transaction = session.BeginTransaction();
Customer John = new Customer { Name="John" };
Invoice invoice1 = new Invoice
{
Date = DateTime.Now.AddDays(-1),
Amount = 100
};
Invoice invoice2 = new Invoice
{
Date = DateTime.Now,
Amount = 200
};
John.Invoices = new List<Invoice>{invoice1, invoice2};
session.Save(John);
transaction.Commit();
transaction.Dispose();
session.Dispose();
sessionFactory.Dispose();
}
catch(Exception e)
{
Console.WriteLine(e);
}
}
}
}
[/code]
fails with the following exception :
[code]
NHibernate.Exceptions.GenericADOException: could not insert:
[CRM.Invoice][SQL:
INSERT INTO invoices (date, amount) VALUES (?, ?)] --->
MySql.Data.MySqlClient.M
ySqlException: Field 'customer_id' doesn't have a default value
[/code]
So apparently NHibernate ignores the one-to-many relationship and
tries to persist the invoices before the customer, which fails because
the "customer_id" field has no default value, and particularly cannot
be null.
Of course when I remove the "not null" constraint on the foreign key
"customer_id" all is working fine because NHibernate :
- persists the invoices assigning them a null "customer_id",
- persists the customer and assign the right "customer_id" to the
invoices
or something like that.
But I can't change the legacy relational model.
1) Does it exist, in the mapping file, a way to make NHibernate taking
into account the relationship when persisting a Customer ?
2) If not is there a programmatic way of doing so ?
Thanks in advance.
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