My model object Reading has a Location but it's not a direct relationship in the database. In the DB, this "has-a" relationship or "reference" spans 3 tables, as shown in this snip:
My Reading maps to the ComponentReading table and i want my Location to map to the Location table. My ClassMap<Reading> class looks like this for now:
public class ReadingMap : ClassMap<Reading>
{
public ReadingMap()
{
Table("ComponentReading");
Id(x => x.ID).Column("ComponentReadingId");
//References(x => x.Location).Formula(
Join("VehicleReading", vr =>
{
Join("TrainReading", tr =>
{
tr.References(x => x.Location, "LocationId");
});
});
Map(x => x.TemperatureValue).Column("Temperature");
}
}
And here is my simple Location mapping:
public class LocationMap : ClassMap<Location>
{
public LocationMap()
{
Id(x => x.ID).Column("LocationId");
Map(x => x.Name);
}
}
The commented References( method sort of shows what i want to achieve with the relationship between Reading and Location but obviously i can't express it to FNH as simply as the commented line suggests.
I don't think the Join( code is even nearly correct either, but it also tries to communicate the relationship that i'm after.
I hope someone can see what i'm trying to do here. Can you help me?
This question is related.
I think you cant nest joins that way. An ugly but pragmatic solution would be (untested):
class Reading
{
public virtual int ID { get; set; }
protected virtual Hidden.TrainReading m_trainReading;
public virtual Location Location
{ get { return m_trainReading.Location; } set { m_trainReading.Location = value; } }
public virtual int TemperatureValue { get; set; }
}
namespace Hidden
{
class TrainReading
{
public virtual int ID { get; set; }
public virtual int VehicleReadingId { get; set; }
public virtual Location Location { get; set; }
}
}
public class ReadingMap : ClassMap<Reading>
{
public ReadingMap()
{
Table("ComponentReading");
Id(x => x.ID).Column("ComponentReadingId");
References(Reveal.Member<Reading, Hidden.TrainReading>("m_trainReading"), "");
Map(x => x.TemperatureValue).Column("Temperature");
}
}
public class TrainReadingMap : ClassMap<Hidden.TrainReading>
{
public TrainReadingMap()
{
Table("TrainReading");
Id(x => x.ID).Column("TrainReadingId");
References(x => x.Location, "LocationId");
Join("VehicleReading", vr =>
{
vr.KeyColumn("TrainReadingId");
vr.Map(x => x.VehicleReadingId, "VehicleReadingId");
});
}
}
Related
I have the following classes defined:
And these tables in my database:
My fluent NHibernate mappings are:
public class BusinessUnitMap : ClassMap<BusinessUnit>
{
public BusinessUnitMap()
{
Table("BusinessUnits");
Id(x => x.Id);
Map(x => x.Code);
Map(x => x.Name);
Map(x => x.ParentId);
Map(x => x.Type).Column("Type").CustomType<BusinessUnitType>();
}
}
public class CompanyMap : SubclassMap<Company>
{
public CompanyMap()
{
Table("CompanyData");
KeyColumn("BusinessUnitID");
Map(x => x.Something);
}
}
public class FranchiseeMap : SubclassMap<Franchisee>
{
public FranchiseeMap()
{
Table("FranchiseeData");
KeyColumn("BusinessUnitID");
Map(x => x.SomethingDifferent);
}
}
public class StoreMap : SubclassMap<Store>
{
public StoreMap()
{
Table("StoreData");
KeyColumn("BusinessUnitID");
Map(x => x.SomethingElse);
}
}
Question #1
As far as I can tell, my code and database are setup the same as every example I've been able to find. According to those articles, NHibernate is supposed to be smart enough to determine what subclass to instantiate when I query for a particular subclass. But, when I execute the following statement:
var result = Session.QueryOver<BusinessUnit>()
.Where(x => x.Code == "Acme")
.SingleOrDefault();
an exception is thrown because it can't create an instance of the abstract BusinessUnit class. The only way I can get this to work is to specify Company as the type argument for QueryOver.
I've confirmed that using a discriminator breaks since NHibernate is looking for all of the columns to exist in a single table. Without it, though, I struggle to see how NHibernate would know what type to instantiate.
What am I doing wrong? Is the problem in my mappings, the way I'm querying, ...?
Question #2
When I change the query to something like this:
public T WithCode<T>(String code)
where T : BusinessUnit
{
var result = Session.QueryOver<T>()
.Where(x => x.Code == code)
.SingleOrDefault();
return result;
}
I get an exception indicating that the UPDATE statement conflicts with a foreign key constraint. Update statement!!!! Clearly something is still not right. How can a QueryOver call result in an UPDATE statement? What am I missing?
it looks like your data is not consistent. It might be better to use discrimnator mapping with optional. If you dont really need a BusinessUnitType property in code then just delete everything around the property Type
public enum BusinessUnitType
{
Company,
Franchisee
}
public abstract class BusinessUnit
{
public virtual int Id { get; set; }
public virtual string Code { get; set; }
public virtual string Name { get; set; }
public virtual BusinessUnit Parent { get; set; }
public abstract BusinessUnitType Type { get; }
}
public class Company : BusinessUnit
{
public virtual string Something { get; set; }
public override BusinessUnitType Type { get { return BusinessUnitType.Company; } }
}
public class Franchisee : BusinessUnit
{
public virtual string SomethingDifferent { get; set; }
public override BusinessUnitType Type { get { return BusinessUnitType.Franchisee; } }
}
public class BusinessUnitMap : ClassMap<BusinessUnit>
{
public BusinessUnitMap()
{
Table("BusinessUnits");
Id(x => x.Id);
Map(x => x.Code);
Map(x => x.Name);
References(x => x.Parent);
DiscriminateSubClassesOnColumn("Type");
Map(x => x.Type, "Type")
.Access.None()
.CustomType<BusinessUnitType>().ReadOnly();
}
}
public class CompanyMap : SubclassMap<StrangeTablePerSubclass.Company>
{
public CompanyMap()
{
DiscriminatorValue((int)new Company().Type);
Join("CompanyData", join =>
{
join.KeyColumn("BusinessUnitID");
join.Optional();
join.Map(x => x.Something);
});
}
}
public class FranchiseeMap : SubclassMap<Franchisee>
{
public FranchiseeMap()
{
DiscriminatorValue((int)new Franchisee().Type);
Join("FranchiseeData", join =>
{
join.KeyColumn("BusinessUnitID");
join.Optional();
join.Map(x => x.SomethingDifferent);
});
}
}
I am trying to map two tables :
the first one has an id (idA) and a field with the id (idB) of the other table.
the other one has a composite key based on the previous id (idB) and an other one (idB2)
The idea is that the second table contains the description of A split on multiple rows.
My current implementation is the following but I am unable to retrieve the partialDescription needed for concatenation.
How should I change my mapping to work? Any ideas? :)
public class A
{
long idA
lond idB
string fullDescription
}
public class B
{
long idB
long idB2
strind partialDescription
}
public class AMap : ClassMap<A>
{
public AMap()
{
Table("A");
Id(x => x.id).Column("idA").GeneratedBy.Native();
Map(x => x.idB).Column("idB")
HasMany(x => x.B).KeyColumn("idB").Inverse().Cascade.All().Not.LazyLoad();
}
}
public class BMap : ClassMap<B>
{
public BMap()
{
Table("B");
CompositeId()
.KeyReference(x => x.A, "idB")
.KeyProperty(x => x.idB2, "idB2");
Map(x => x.partialDescription, "desc").CustomType("AnsiString");
}
}
In fact, by your description, you must have this another scenario:
public class A
{
public virtual long Id { get; set; }
public virtual IList<B> PartialDescriptions { get; protected set; }
public string fullDescription
{
get
{
StringBuilder description = new StringBuilder();
foreach (var partial in PartialDescriptions)
{
description.Append(partial);
}
return description.ToString();
}
}
}
public class B
{
public virtual long Id { get; set; }
public virtual long Id2 { get; set; }
public virtual string Description { get; set; }
}
Then, try to implement your class maps like this:
public class BMap : ClassMap<B>
{
public BMap()
{
Table("B");
CompositeId()
.KeyReference(x => x.Id, "idB")
.KeyProperty(x => x.Id2, "idB2");
Map(x => x.partialDescription, "desc").CustomType("AnsiString");
}
}
public class AMap : ClassMap<A>
{
public AMap()
{
Table("A");
Id(x => x.Dd).Column("idA").GeneratedBy.Native();
HasMany(x => x.PartialDescriptions)
.KeyColumn("idB")
.Inverse()
.Cascade.All()
.Not.LazyLoad();
}
}
NOTE: I didn't tried to compile this code. I only expect that you can take the general .
I recommend you that take a look into Getting started section of Fluent NHibernate to more information.
What's wrong with my mapping shown below? Is this a problem with GeneratedBy.Foreign()? How should I use it cause my PK in UserTable(UID) is also the FK which refers to PersonTable PK(PID). I get the Duplicate class/entity mapping consoleMappingTest.SystemUser error. what do you suggest(be sure to look at database structure- no way to change it). thanks.
Inheritance structure:
public class Person
{
public virtual int ID { get; set; }
}
public class User:Person
{
public override int ID
{
get
{
return base.ID;
}
set
{
base.ID = value;
}
}
public virtual string Name { get; set; }
public virtual int Salary { get; set; }
}
public class SystemUser:User
{
public virtual int Password { get; set; }
}
Database structure:
for saving some info about person(some fields not shown here):
PersonTable(PID)
for saving User and all it's subclasses like system user:
UserTable(UID,Name,Salary,Type)
and here is my mapping:
public class PersonMap : ClassMap<Person>
{
public PersonMap()
{
Table("PersonTable");
Id(x => x.ID, "PID").GeneratedBy.Assigned();//or HiLo-not important
}
}
public class UserMap : ClassMap<User>
{
public UserMap()
{
Table("UserTable");
DiscriminateSubClassesOnColumn("Type").Default("U");
Id(x => x.ID, "UID").GeneratedBy.Foreign("Person");//how should use this?
Map(x => x.Salary);
Join("PTable", j =>
{
j.KeyColumn("UID");
j.Map(x => x.Name);
});
}
}
public class SystemUserMap : SubclassMap<SystemUser>
{
public SystemUserMap()
{
DiscriminatorValue("SU");
Map(x => x.Password);
}
}
Foreign("") is meant to point to a Reference (Property with another mapped entity) from which the Id should be retrieved. You don't have a Reference to class Person named Person so you can't use it like this.
you already asked the same question with an answer. I know i didn't do it right first shot but would be nice if you told me what doesnt work with the latest edit or you dont like the solution befor asking the same question again
I have couple of classes and want to map them correctly to database:
public class A
{
public virtual Guid Id { get; private set; }
public virtual ComponentClass Component { get; set; }
}
public class ComponentClass
{
public virtual IList<B> Elements { get;set; }
}
public class B
{
public virtual Guid Id { get; private set; }
public virtual DateTime Time { get; set; }
}
I map them using fluent mappings like that:
public class AMap : ClassMap<A>
{
public A() {
Id(x => x.Id);
Component(x => x.Component,
c => c.HasMany(x => x.Elements).Inverse().Cascade.All());
}
}
public class BMap : ClassMap<B>
{
public B() {
Id(x => x.Id);
Map(x => x.Time);
}
}
When I save my entity, I have class A mapped to one table and class B to another as expected.
But I have nulls in Component_id column.
Can you tell me what am I missing here?
I believe Components are supposed to be in the same table , as clearly stated in Ayende's blog post, as they serve only to make the data better represented as an object model. Be sure to read through his blog, it's probably one of the best nHibernate resources out there.
Ok, I've resolved my problem - I can use Id of my "parent" class. So the component mapping will become:
public class AMap : ClassMap<A>
{
public A() {
Id(x => x.Id);
Component(x => x.Component,
c => c.HasMany(x => x.Elements).Cascade.All().Column("Id"));
}
}
So obvious as I look at it now ... but It took me an hour.
If you have a one-to-many association direct to a collection of components (ie. without the ComponentClass wrapper as per the question) then you can map it directly:
HasMany(x => x.Elements)
.AsSet()
.Table("ElementTable")
.KeyColumn("KeyColumn")
.Cascade.All()
.Component(x =>
{
x.Map(c => c.Id);
x.Map(c => c.Time);
})
.LazyLoad();
I have tried various approaches to mapping the following structure, but I finally admit that after a day of not getting very far, I need some help.
So the question is, how would you guys go about mapping something like this. The schema is not fixed at this point.
public abstract class BaseObject
{
public virtual int Id { get; set; }
public virtual string Name { get; set; }
public virtual string Description { get; set; }
public virtual string Prefix { get; set; }
public virtual string Suffix { get; set; }
public virtual BaseObject Parent { get; set; }
}
public class Room : BaseObject
{
public virtual int AreaId { get; set; }
}
public class Item : BaseObject
{
public virtual string Owner { get; set; }
public virtual IList<ItemAttribute> Attributes { get; set; }
public virtual int ItemTypeId { get; set; }
}
public class Potion : Item
{
public virtual int AmountLeft { get; set; }
}
Your input is very much appreciated.
This allows you to have it all in one table... doing this from memory, so syntax might not be exact.
public class ItemMap : ClassMap<BaseObject>
{
...
WithTable("objects");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Name);
Map(x => x.Description);
...
DiscriminateSubClassesOnColumn("Type")
.SubClass<Room>("Room", x =>
{
x.Map(r => r.AreaId);
})
.SubClass<Item>("Item", c =>
{
i.Map(x => x.Owner);
i.References(x => x.Account).LazyLoad();
HasManyToMany(x => x.Attributes)
.WithParentKeyColumn("ItemId")
.WithChildKeyColumn("AttributeId")
.WithTableName("ItemAttributes")
.LazyLoad();
});
.SubClass<Potion>("Potion", x =>
{
x.Map(p => p.AmountLeft);
})
I would probably have a table for each class - Room, Item, Potion and then do fairly standard mappings for each.
I'd like to note that in my own experiences, it is a bad idea to name your Id field in your business objects "Id"
Here's a sample with Item, assoming some data names for your table.
public class ItemMap : ClassMap<Item>
{
public ItemMap()
{
WithTable("Items");
Id(x => x.Id, "ItemId").GeneratedBy.Identity();
Map(x => x.Name);
Map(x => x.Description);
Map(x => x.Prefix);
Map(x => x.Suffix);
Map(x => x.Owner);
Map(x => x.ItemTypeId);
References<Item>(x => x.Parent, "ParentItemId");
HasManyToMany(x => x.Attributes)
.WithParentKeyColumn("ItemId")
.WithChildKeyColumn("AttributeId")
.WithTableName("ItemAttributes")
.LazyLoad();
}
}
This is more than likely not be perfect - as I'm not sure how the mapping will work with the abstract parent.