I´m using Fluent Nhibernate with automapping and having problem setting up a bi-directional HasMany relationship because of my current inheritance.
I simplified version of my code looks like this
public abstract class BaseClass
{
public BaseClass Parent { get; set; }
}
public class ClassA : BaseClass
{
public IList<ClassB> BChilds { get; protected set; }
public IList<ClassC> CChilds { get; protected set; }
}
public class ClassB : BaseClass
{
public IList<ClassD> DChilds { get; protected set; }
}
public class ClassC : BaseClass
{
}
public class ClassD : BaseClass
{
}
Every class can have one parent and some parents can have childs of two types. I´m using table-per-type inheritance which result in the tables
"BaseClass"
"ClassA"
"ClassB"
"ClassC"
"ClassD"
To get a working bi-directional mapping I have made the following overrides
(one example from ClassA)
mapping.HasMany<BaseType>(x => x.BChilds).KeyColumn("Parent_Id");
mapping.HasMany<BaseType>(x => x.CChilds).KeyColumn("Parent_Id");
This works fine on classes with only one type of children, but ClassA with two child types will get all subtypes of BaseType in each list which ofcourse will end up in an exception. I have looked at two different workarounds tho none of them feels really sufficient and I really believe there is a better way to solve it.
Workaround 1: Point to the concrete subtype in the HasMany mapping. (Updated with more info)
mapping.HasMany<ClassB>(x => x.BChilds).KeyColumns("Parent_Id");
(BaseType replaced with ClassB)
With this mapping NHibernate will in some cases look in the ClassB table for a column named Parent_Id, obviously there is no such column as it belongs to the BaseClass table. The problem only occurs if you add a statement based on BChilds during a ClassA select. e.g loading an entity of ClassA then calling ClassA.BChilds seems to work, but doing a query (using NhibernateLinq) something like
Query<ClassA>().Where(c => c.BChilds.Count == 0)
the wrong table will be used. Therefore I have to manually create a new column in this table with the same name and copy all the values. It works but it´s risky and not flexible at all.
Workaround 2: Add a column to the BaseClass that tells the concrete type and add a where statement to the HasMany mapping.
(after my update to workaround1 I´m no longer sure if this could be a workable solution)
By adding a column they same way as it´s done when using table-per-hierarchy inheritance with a discriminatorValue. i.e BaseType table will get a new column with a value of ClassA, ClassB... Tho given how well NHibernate handles the inheritance overall and by reading the NHibernate manual I believe that the discriminator shouldn´t be needed in a table-per-type scenario, seems like Nhibernate already doing the hardpart and should be able to take care of this in a clean way to without adding a new column, just can´t figure out how.
What's your base class mapping and what does your subclass map look like?
You should be able to do
mapping.HasMany(x => x.BChilds);
And with the correct mapping, you shouldn't have a problem.
If it's fluent nhibernate, look into
UseUnionSubclassForInheritanceMapping();
Related
I am trying to map following domain model using union-subclass strategy and FluentNHibernate. Here is how my classes look (with unneeded parts removed)
public class Benefit
{
}
public class Leave : Benefit
{
}
public class SeasonTicketLoan : Benefit
{
}
And here is my mapping code
public class BenefitMappings : ClassMap<Benefit>
{
public BenefitMappings()
{
UseUnionSubclassForInheritanceMapping();
}
}
public class LeaveMappings : SubclassMap<Leave>
{
}
public class SeasonTicketLoanMappings : SubclassMap<SeasonTicketLoan>
{
}
When I generate a database script using SchemaExport for the above mapping, I get a table for Leave and another one for SeasonTicketLoan but none for Benefit. Am I missing anything here?
...Am I missing anything here?
Yes, you are using mapping Table Per Concrete Class (TPC), Which is intended to create
separate table per each class and
NO table for parent.
To get really deep and clear understanding, you should read this comprehensive article:
Inheritance mapping strategies in Fluent Nhibernate
Where you can read:
Table Per Concrete Class (TPC)
In TPC inheritance, every class in an inheritance hierarchy will have its own table. The inheritance hierarchy masks the fact that there are several independent underlying tables representing each subtype.
code snippet extract:
// mapping of the TPCBaseEntity base class
public class TPCBaseEntityMap : ClassMap<TPCBaseEntity>
{
public TPCBaseEntityMap()
{
// indicates that this class is the base
// one for the TPC inheritance strategy and that
// the values of its properties should
// be united with the values of derived classes
UseUnionSubclassForInheritanceMapping();
In case, we would like to have also table per base class(es), we need:
Table Per Type(TPT)
TPT is an inheritance described in the database with separate tables. Every table provides additional details that describe a new type based on another table which is that table’s parent.
again some mapping snippet extract:
// mapping of the TPTAnimal base class
public class TPTAnimalMap : ClassMap<TPTAnimal>
{
public TPTAnimalMap()
{
// the name of the schema that stores the table corresponding to the type
Schema("dbo");
// the name of the table corresponding to the type
Table("TPT_Animal");
...
// mapping of the TPTHorse class
public class TPTHorseMap : SubclassMap<TPTHorse>
{
public TPTHorseMap()
{
// the name of the schema that stores the table corresponding to the type
Schema("dbo");
// the name of the table corresponding to the type
Table("TPT_Horse");
I'm trying to automap a simple inheritance hierarchy with Fluent Nhibernate, and I need to have a slightly different name for each table than its class (underscores instead of Pascal case). This seems like an obvious place to use conventions. I also want to use the table-per-subclass strategy, but the combination seems to be causing me an issue: the convention is only applied to the base class of the hierarchy.
Here's my automapping:
AutoMap
.AssemblyOf<BaseRule>()
.IncludeBase<BaseRule>() // "BaseRule" is an abstract class
.Conventions.Add( DefaultCascade.All() )
.Conventions.Add<OracleTableNameConvention>()
How I want my classes mapped (class name -> table name):
abstract class BaseRule -> Base_Rule
class NumberRule : BaseRule -> Number_Rule
class PatternStringRule : BaseRule -> Pattern_String_Rule
What I'm actually getting:
BaseRule -> Base_Rule
NumberRule -> NumberRule
PatternStringRule -> PatternStringRule
As you can see, only the base class is actually being changed. Here's my existing convention, just so you can see how I'm defining it:
public class OracleTableNameConvention : IClassConvention
{
public void Apply(IClassInstance instance)
{
string fixedName = instance.EntityType.Name.ToUnderscoredNaming();
instance.Table(fixedName);
}
}
I've also looked into the ISubclassConvention interface, and can see no way in there to adjust the name of the table (which makes enough sense, subclasses aren't always in their own table).
If I delete the IncludeBase line from my automapping, the names become what I want, except it becomes table-per-concrete-class. I want to use table-per-subclass, leaving all the common data in one shared base table.
I can add overrides for each name, and I will if I have to, but I'd rather not.
It seems like this should be an obviously supported behavior. How can I have the naming convention apply to each table in the hierarchy, without going to table-per-concrete-class?
As soon as I posted this question, I figured it out.
IJoinedSubclassConvention is the interface I needed to implement.
public class OracleSubClassConvention : IJoinedSubclassConvention
{
public void Apply(IJoinedSubclassInstance instance)
{
string fixedName = instance.EntityType.Name.ToUnderscoredNaming();
instance.Table(fixedName);
}
}
I found it by looking for anything that had a method Table(string).
I have the inheritance described below :
public abstract class BaseEntity<TId> {....}
public abstract class ModelEntity : BaseEntity<Int32>{....}
public abstract class AuditableEntity : ModelEntity,IAuditable{....}
public class ApplicationUser : AuditableEntity{....}
public class SuperUser : ApplicationUser
I am using NHibernate 3.3 and I want to Create the mappings for that inheritance
public abstract class ModelEntityMap<TEntity> : ClassMapping<TEntity>
where TEntity : ModelEntity
{...}
public class AuditableEntityMap<TEntity> : ModelEntityMap<TEntity> where TEntity : AuditableEntity
{ ...}
public class ApplicationUserMap : AuditableEntityMap<ApplicationUser>
{...}
public class SuperUserMap : JoinedSubclassMapping<SuperUser>{...}
When the application starts and trys to set up the database it raises the following Exception :
Ambiguous mapping for SuperUser More than one root entities was found BaseEntity / ApplicationUser
Possible solutions
-Merge the mapping of root Entity in the one is representing the real root in the hierarchy
-Inject a IModelInspector with a logic to discover the real root-entity.
I was using Fluent nhibernate with the same inheritance and worked fine with SuperUserMap defined as
public class SuperUserMap : SubClassMap {...}
I am new to Nhibernate mapping by code and quite confused !!!
I believe there are two ways to solve this problem:
a) Using the concept of discriminator that identifies the type of the class stored and thereby the right object is retrieved from the database, in this case your class is mapped to a table that has all the columns plus the discriminator columns. Not sure how this works with multi-level inheritance but this is something that you can google.
b) take a look at this post on how he deals with inheritance: http://fabiomaulo.blogspot.co.nz/2011/04/nhibernate-32-mapping-by-code_13.html you might get some idea to solve your issue.
You can influence the decision whether an entity is a root entity by overriding the IsRootEntity logic of the model mapper that you use to create mappings.
Here's an example that defines the default NHibernate mapping-by-code behaviour:
var modelMapper = new ConventionModelMapper();
modelMapper.IsRootEntity((type, declared) =>
{
if (declared) return true; // Type has already been declared as root entity
return type.IsClass
&& typeof(object) == type.BaseType
&& modelMapper.ModelInspector.IsEntity(type);
});
You will have to tweak this decision logic to exclude the BaseEntity class as possible root entity.
I had this error with NHibernate 4.1.1 (May 2017), so I'm answering with how I solved it for future reference
In my case, I copied an existing mapping of an inheriting class, and forgot to change the parent mapping class to ClassMapping and encountered the same error
In other words, in your mapping class, check the parent class, make sure it is ClassMapping or JoinedSubclassMapping if it's a child class
This is my first time trying Fluent NHibernate and Auto mapping. Unfortunately I have run into an issue that I cannot get past. I'm getting an error saying that a method on one of my classes cannot be mapped.
public class Person
{
public IEnumerable<string> GetStuff(){return stuff;}
}
The Exception Message is:
The entity '<GetStuff>d__0' doesn't have an Id mapped.
I even tried adding an IAutoMappingOverride to ignore the method (using map.IgnoreProperty).
Is it really trying to map a method? whats going on here?
Every entity that you want to Automap must have an Id property, or inherit from a class that has an Id property. Your Person class does neither.
Also, in my experience, all public methods in entities must be declared virtual (though this may not be required if you eager load everything).
I got around this by manually marking each Entity with an interface.
public class MyAutomappingConfiguration : DefaultAutomappingConfiguration
{
public override bool ShouldMap(Type type)
{
return type.GetInterfaces().Contains(typeof (IEntity));
}
}
I've found a number of posts about this but none seem to help me directly. Also there seems to be confusion about solutions working or not working during different stages of FluentNHibernate's development.
I have the following classes:
public class MappedClass
{
...
}
public enum MyEnum
{
One,
Two
}
public class Foo
{
...
public virtual IDictionary<MappedClass, MyEnum> Values { get; set; }
}
My questions are:
Will I need a separate (third) table of MyEnum?
How can I map the MyEnum type? Should I?
What should Foo's mapping look like?
I've tried mapping HasMany(x => x.Values).AsMap("MappedClass")...
This results in: NHibernate.MappingException : Association references unmapped class: MyEnum
It looks like this questions is a duplicate of Fluent code for mapping an IDictionary<SomeEntity, int>?. The solution was to use hbm.xml to map a ternary association table. It looks like at the time FluentNHibernate's AsTernaryAssocation() method only worked for entity types. I can't tell if this has changed, or if it is a planned feature.