Using ConfORM with modular application

I’m getting some questions about how use ConfORM in modular applications. The first commercial application mapped with ConfORM is a pretty complex modular application and if you have a look to the first ConfOrm example you can find the IModuleMapping.
Here I’ll try to explain how we have used it in that application writing a new example.

The IModuleMapper

/// <summary>
/// A template to perform a mapping using ConfOrm
/// </summary>
public interface IModuleMapper
{
    /// <summary>
    /// Register domain classes, persistent-strategies, relations and so on of a spefic module
    /// </summary>
    void DefineDomain();

    /// <summary>
    /// Register patterns of a module
    /// </summary>
    void RegisterPatterns();

    /// <summary>
    /// Customize persistence representations
    /// </summary>
    void Customize();

    /// <summary>
    /// Get all domain entities of the module.
    /// </summary>
    /// <returns>domain entities.</returns>
    IEnumerable<Type> GetEntities();
}

As you can see it is a simple template just to suggest how organize your mapping… nothing complicated.

The Domain

In the assembly Acme.ModuleA

using System;
using Acme.Domain.Common;

namespace Acme.ModuleA
{
    public class User: Entity
    {
        public string UserName { get; set; }
        public string Text { get; set; }
        public DateTime Birthday { get; set; }
    }
}

In the assembly Acme.ModuleB

using System;
using Acme.Domain.Common;
using Acme.ModuleA;

namespace Acme.ModuleB
{
    public class Article: Entity
    {
        public DateTime PublishedAt { get; set; }
        public string Title { get; set; }
        public string Text { get; set; }
        public User Author { get; set; }
    }
}

Some extensions

Just to not forget it later…

public static class ModuleMappingUtil
{
    public static IEnumerable<Type> MapModule(this IModuleMapper mapper)
    {
        mapper.DefineDomain();
        mapper.RegisterPatterns();
        mapper.Customize();
        return mapper.GetEntities();
    }

    public static bool IsOfModuleContaining<T>(this Type source)
    {
        return source.Assembly.Equals(typeof(T).Assembly);
    }
}

The mapping

You can organize the mapping of your modules in a single assembly, in general the same where you are generating the session factory, or in more than one assembly. In general you need just a little class to map a module so please don’t be exaggerated separating your application.
For this example I will show three implementations of ModuleMapper all implemented in the same assembly named Acme.Persistence.Wiring.

public class GeneralsPatternsModuleMapper : IModuleMapper
{
    private readonly Mapper mapper;
    private readonly ObjectRelationalMapper orm;

    public GeneralsPatternsModuleMapper(ObjectRelationalMapper orm, Mapper mapper)
    {
        this.orm = orm;
        this.mapper = mapper;
    }

    #region IModuleMapper Members

    public void DefineDomain()
    {
        // map .NET4 ISet<T> as a NHibernate's set
        orm.Patterns.Sets.Add(mi => mi.GetPropertyOrFieldType().GetGenericIntercafesTypeDefinitions().Contains(typeof (ISet<>)));
    }

    public void RegisterPatterns()
    {
        // all strings are length 50 characters
        mapper.PatternsAppliers.Property.Add(mi => typeof (string).Equals(mi.GetPropertyOrFieldType()), (mi, map) => map.Length(50));
      
        // when a DateTime seems to be a simple date apply NH's Date type
        mapper.PatternsAppliers.Property.Add(mi => typeof (DateTime).Equals(mi.GetPropertyOrFieldType()) && IsDate(mi.Name), (mi, map) => map.Type(NHibernateUtil.Date));

        // when a DateTime seems to not be a simple date apply NH's UtcDateTime type
        mapper.PatternsAppliers.Property.Add(mi => typeof (DateTime).Equals(mi.GetPropertyOrFieldType()) && !IsDate(mi.Name), (mi, map) => map.Type(NHibernateUtil.UtcDateTime));
    }

    public void Customize()
    {
        // Nothing to do
    }

    public IEnumerable<Type> GetEntities()
    {
        yield break;
    }

    #endregion

    public static bool IsDate(string name)
    {
        return name.EndsWith("Date") || name.StartsWith("Date") || name.EndsWith("Day") || name.EndsWith("day") || name.StartsWith("Day");
    }
}

The GeneralsPatternsModuleMapper register just part of my common convention for the current application. Then the mapping of my Acme.ModuleA:

public class ModuleAMapper : IModuleMapper
{
    private readonly Mapper mapper;
    private readonly ObjectRelationalMapper orm;

    public ModuleAMapper(ObjectRelationalMapper orm, Mapper mapper)
    {
        this.orm = orm;
        this.mapper = mapper;
    }

    public void DefineDomain()
    {
        // register all classes of my module (ConfORM will use it to discover polymorphic associations)
        orm.AddToDomain(typeof(User).Assembly.GetExportedTypes());

        // defines the persistence strategy for each root of each hierarchy
        orm.TablePerClass<User>();
    }

    public void RegisterPatterns()
    {
        // no specific patterns for this module
    }

    public void Customize()
    {
        // map a specific size (20) for a specific property of a specific class
        mapper.Class<User>(x => x.Property(user => user.UserName, map => map.Length(20)));
    }

    public IEnumerable<Type> GetEntities()
    {
        // all entities of this modules
        return typeof(User).Assembly.GetExportedTypes().Where(t=> typeof(Entity).IsAssignableFrom(t));
    }
}

The mapping of Acme.ModuleB:

public class ModuleBMapper : IModuleMapper
{
    private readonly Mapper mapper;
    private readonly ObjectRelationalMapper orm;

    public ModuleBMapper(ObjectRelationalMapper orm, Mapper mapper)
    {
        this.orm = orm;
        this.mapper = mapper;
    }

    public void DefineDomain()
    {
        // register all classes of my module (ConfORM will use it to discover polymorphic associations)
        orm.AddToDomain(typeof(Article).Assembly.GetExportedTypes());

        // defines the persistence strategy for each root of each hierarchy
        orm.TablePerClassHierarchy<Article>();
    }

    public void RegisterPatterns()
    {
        // patterns for this module

        // when a string property is named "Text" then apply StringClob type (note just for Acme.ModuleB)
        mapper.PatternsAppliers.Property.Add(
            mi => "text".Equals(mi.Name.ToLowerInvariant()) && typeof (string).Equals(mi.GetPropertyOrFieldType()) && mi.DeclaringType.IsOfModuleContaining<Article>(),
            (mi, map) => { map.Type(NHibernateUtil.StringClob); map.Length(int.MaxValue); });
    }

    public void Customize()
    {
        // nothing to do
    }

    public IEnumerable<Type> GetEntities()
    {
        // all entities of this modules
        return typeof(Article).Assembly.GetExportedTypes().Where(t => typeof(Entity).IsAssignableFrom(t));
    }
}

The NHibernate’s initialization

First you need a method to get all modules of your application, for simplicity here is a simple implementation:

private static IEnumerable<IModuleMapper> GetAllModulesMappers(ObjectRelationalMapper orm, Mapper mapper)
{
    yield return new GeneralsPatternsModuleMapper(orm, mapper);
    yield return new ModuleAMapper(orm, mapper);
    yield return new ModuleBMapper(orm, mapper);
}

and now you have all is needed to have the session factory:

var orm = new ObjectRelationalMapper();
var patternSet = new CoolPatternsAppliersHolder(orm);
var mapper = new Mapper(orm, patternSet);
 
HbmMapping mappings = mapper.CompileMappingFor(GetAllModulesMappers(orm, mapper).SelectMany(x => x.MapModule()));
 
var configure = new Configuration();
configure.SessionFactoryName("Demo");
configure.DataBaseIntegration(db =>
{
    db.Dialect<MsSql2008Dialect>();
    db.ConnectionStringName = "ToAcmeDb";
});
 
configure.AddDeserializedMapping(mappings, "AcmeApplicationDomain");
 
ISessionFactory factory = configure.BuildSessionFactory();

In the line 5 I’m getting just one mapping document for the whole domain. You can use the methodmapper.CompileMappingForEach without problems. The main matter here is the fact that I’m using just one instance of ObjectRelationalMapper and Mapper to give the whole picture of the domain of the application to ConfORM.