I'm starting to learn NHibernate (3.0) and picked up a copy of Packt Publishing's NHibernate 3.0 Cookbook.
There's a section on one-to-many mappings which I'm walking through but with my own database. It suggests I should do something like this to model a one to many relationship between customers and their domains:
public class Customer
{
public virtual int Id { get; protected set; }
public virtual string CustomerName { get; set; }
// Customer has many domains
public virtual IList<Domain> Domains { get; set; }
}
public class Domain
{
public virtual int Id { get; protected set; }
public virtual int CustomerID { get; set; }
public virtual string DomainName { get; set; }
}
Customer Mapping:
<class name="Customer" table="tblCustomer">
<id name="Id">
<column name="CustomerID" sql-type="int" not-null="true"/>
<generator class="identity"/>
</id>
<property name="CustomerName" column="Customer"/>
<list name="Domains">
<key column="CustomerID"/>
<one-to-many class="Domain" />
</list>
</class>
When I run this I get the following error:
XML validation error: The element 'list' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'one-to-many' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'index, list-index' in namespace 'urn:nhibernate-mapping-2.2'.
The book's example is a bit more complex in that they use table-per-subclass mappings:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="Eg.Core"
namespace="Eg.Core">
<subclass name="Movie" extends="Product">
<property name="Director" />
<list name="Actors" cascade="all-delete-orphan">
<key column="MovieId" />
<index column="ActorIndex" />
<one-to-many class="ActorRole"/> <-- Is this wrong?
</list>
</subclass>
</hibernate-mapping>
I'm guessing the book is wrong?
No, your mapping is missing the index element. A list in NHibernate is an ordered set, if you want an unordered set use bag mapping.
Related
I have two classes:
namespace fm.web
{
public class User
{
public static string default_username = "guest";
public static string default_password = "guest";
private UserType usertype;
public virtual int? Id { get; set; }
public virtual string Username { get; set; }
public virtual string Password { get; set; }
public virtual DateTime Datecreated { get; set; }
public virtual string Firstname { get; set; }
public virtual string Lastname { get; set; }
public virtual string Email { get; set; }
public virtual UserType Usertype
{
get { return usertype; }
set { usertype = value; }
}
}
}
namespace fm.web
{
public class UserType
{
public virtual int? Id { get; set; }
public virtual string Title { get; set; }
}
}
Here are the mapping files
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="fm.web"
assembly="fm.web">
<class name="User" table="[user]">
<id name="Id">
<column name="id" />
<generator class="native" />
</id>
<property name="Username" />
<property name="Password" />
<property name="Datecreated" />
<many-to-one name="Usertype"
class="UserType"
column="[type]"
cascade="all"
lazy="false"
/>
<property name="Firstname" />
<property name="Lastname" />
<property name="Email" />
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="fm.web"
assembly="fm.web">
<class name="UserType" table="[user_type]">
<id name="Id">
<column name="id" />
<generator class="native" />
</id>
<property name="Title" />
</class>
</hibernate-mapping>
I'm getting an exception: DuplicateMappingException
Could not compile the mapping document: fm.web.data.User.hbm.xml
Duplicate class/entity mapping User
Is nhibernate always this hard? Maybe I need a different framework.
I really think the mappings are fine which leads me to believe that the configuration setup is not quite right.
Please can you check that BuildSessionFactory is only called once on application start up.
Also please check that you are not including the mapping files twice as this will also throw this type of error.
Please post your configuration code.
You are correct in thinking that NHibernate is difficult to grasp for new comers espically the session management and mappings. Once you have grasped this then things get easier and are well worth the effort.
I have the following entity:
public class Alert
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IDictionary<CxChannel, string> Messages { get; set; }
}
public enum CxChannel
{
Message,
Email
}
and following mapping:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="Entities.Alert, Entities" table="alert">
<id name="Id" type="int" unsaved-value="0" access="property">
<generator class="identity"/>
</id>
<property name="Name" column="name"/>
<map name="Messages" table="alert_message" cascade="all">
<key column="alert_id"/>
<index column="channel" type="Entities.CxChannel, Entities"/>
<element column="message" type="System.String"/>
</map>
</class>
</hibernate-mapping>
The problem is that when I save an alert entity, Messages dictionary is not persisted to database. As a matter of fact my code looks like the code Oren used in his blog post: http://ayende.com/Blog/archive/2009/06/03/nhibernate-mapping-ndash-ltmapgt.aspx
Has anyone experienced same issue?
Verify that your channel column is an integer in your schema as the CxChannel enum will be mapped as 0 (for Message) and 1 (for email). I just pasted your code and mappings into a console project, used new SchemaExport(cfg).Execute(false, true, false), and successfully inserted rows into the generated database.
I have a class:
public class User
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual IDictionary<string, string> Attributes { get; set; }
}
and a mapping file:
<class name="User" table="Users">
<id name="Id">
<generator class="hilo"/>
</id>
<property name="Name"/>
<map name="Attributes" table="UserAttributes">
<key column="UserId"/>
<index column="AttributeName" type="System.String"/>
<element column="Attributevalue" type="System.String"/>
</map>
</class>
So now I can add many attributes and values to a User.
How can I query those attributes so I can get ie.
Get all the users where attributename is "Age" and attribute value is "20" ?
I don't want to do this in foreach because I may have millions of users each having its unique attributes.
Please help
You can do it using HQL.
For example:
from User u join u.Attributes attr
where index(attr) = 'Age' and attr = '20'
When i map columns from the inspected table, i do this:
<property name="InstanceName" type="MyNameUserType, MyApp.MyNamespace">
<column name="Name"/>
<column name="Name2"/>
</property>
How can I make property mapping initialize a UserType with data retrieved by the formula's sql query?
<property name="InstanceName" type="MyNameUserType, MyApp.MyNamespace" formula="(...)"/>
fails with an exception "wrong number of columns".
Thanks in advance!
MyUserNameType should be a class level mapping so that you can map the result of the SQL function to a class. See these two posts for some possible help:
Class and SQL Function example: http://thoughtspam.spaces.live.com/blog/cns!253515AE06513617!478.entry
NHibernate Mapping with formula mapping example:
http://thoughtspam.spaces.live.com/blog/cns!253515AE06513617!477.entry
I'm the author of the articles referenced by Michael. I had no idea people where still interested and I'm not sure it's applicable with the latest NHibernate.
Here's a fresh link though: http://thoughtspam.wordpress.com/2007/12/19/nhibernate-property-with-formula/
example, using Northwind...
Mapping:
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="PropertyFormulaExample.Shipper, PropertyFormulaExample" table="Shippers" lazy="false" >
<id name="ShipperID" column="ShipperID" unsaved-value="0">
<generator class="native" />
</id>
<property name="CompanyName" column="CompanyName" />
<property name="Phone" column="Phone" />
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="PropertyFormulaExample.Order, PropertyFormulaExample" table="Orders" lazy="false">
<id name="OrderID" column="OrderID" unsaved-value="0">
<generator class="native" />
</id>
<property name="CustomerID" column="CustomerID" />
<property name="ShipVia" type="PropertyFormulaExample.Shipper, PropertyFormulaExample" formula="dbo.GetShipper(shipvia)" />
</class>
</hibernate-mapping>
Entities:
public class Order
{
public int OrderID { get; set; }
public string CustomerID { get; set; }
public Shipper ShipVia { get; set; }
}
public class Shipper : ILifecycle
{
public int ShipperID { get; set; }
public string CompanyName { get; set; }
public string Phone { get; set; }
#region ILifecycle Members
public LifecycleVeto OnDelete(NHibernate.ISession s)
{
throw new NotImplementedException();
}
public void OnLoad(NHibernate.ISession s, object id)
{
}
public LifecycleVeto OnSave(NHibernate.ISession s)
{
throw new NotImplementedException();
}
public LifecycleVeto OnUpdate(NHibernate.ISession s)
{
throw new NotImplementedException();
}
#endregion
}
And finally the SQL function:
CREATE FUNCTION dbo.GetShipper(#shipperId int)
RETURNS int
AS
BEGIN
RETURN #shipperId
END
Obviously, you’ll want the function to do something meaningful, but the idea is you return the PK for the entity and implement ILifecycle.
I've either misunderstood the NHibernate manual or I've done something wrong. Can anyone help?
I am trying to retrieve a User without the AuditLogEntrys.
But NHibernate is still loading the AuditLogEntrys. I only want the AuditLogEntrys loaded when I access the property.
public class User
{
public virtual int UserId { get; set; }
public virtual string UserName { get; set; }
public virtual IList<AuditLogEntry> AuditLogEntrys { get; set; }
}
public class AuditLogEntry
{
public virtual int Id { get; set; }
public virtual DateTime DateRead { get; set; }
public virtual string MachineName { get; set; }
}
Mappings:
<class name="Model.User, Model"
table="User"
lazy="true">
<id name="UserId" access="property" column="UserID">
<generator class="native"></generator>
</id>
<property name="UserName" access="property" />
<bag name="AuditLogEntrys" lazy="true" access="property">
<key column="UserID" />
<one-to-many class="Model.AuditLogEntry, Model"></one-to-many>
</bag>
<class name="Model.AuditLogEntry, Model"
table="AuditLog"
lazy="true">
<id name="Id" access="property" column="ID">
<generator class="native"></generator>
</id>
<property name="DateRead" access="property" column="DateRead"></property>
<property name="MachineName" access="property" column="MachineName"></property>
</class>
Code to get the user:
public IList<User> GetUserByUserName(string userName)
{
ICriteria criteria = NHibernateSession.CreateCriteria(typeof(User))
.Add(Expression.Eq("UserName", userName));
return GetByCriteria(criteria);
}
Now I'd expected a User object with an empty collection of AuditLogEntry's, but this is not what is happening.
Any ideas??
Thanks.
With lazy loading, you will get a populated list of objects, but they are not yet "hydrated" from the database. The lazily-loaded objects are not your entity types, but are instead "proxy objects" which will be populated/hydrated with real data when you access the items in the collection.
The use of proxy objects is the reason why you have to make all of your properties virtual in your entity types. The Proxy types are dynamically-generated subclasses of your entity type, which make the actual calls to the database when you access the properties.
Hopefully I understood your question, but the difference is that you get actual objects back, not an empty list. If you get back an empty list, it means that there were no AuditLogEntry items referencing your User in the database.