Configuring NHibernate in a Multiple Project Layout

I recently had to setup NHibernate in a multiple project c#, asp.net MVC solution. Since most of the tutorials and books only show a basic single project layout I thought I would post an example of how to configure NHiberate with a multi-project solution.

The main problem I had was that my model objects or entity objects were in a separate project than my database access code which contained the .hbm.xml mapping files. When I tried to configure NHibernate with the basic examples I was getting an “NHibernate.MappingException : No persister for: YourClass” exception. I was still getting that exception even after changing the .hbm.xml files to be an “Embedded Resource”. I finally figured out that my .hbm.xml files needed to reference the ModelLayer assebmly and my NHibernate.Cfg.Configuration.AddAssembly() needed to reference the DataAccessLayer assebmly. See screen shots and code examples below for more details.

Solution layout

Model objects Car.cs and CarLot.cs

using System.ComponentModel.DataAnnotations;
namespace MvcAgain.Models {
    public class Car {
        [Required]
        public virtual int Id {get; set;}
        [StringLength(35), Required]
        public virtual string Manufacturer {get; set;}
        [StringLength(35), Required]
        public virtual string Model {get; set;}
        public virtual CarLot Lot {get; set;}
    }
}//end of Car.cs

using Iesi.Collections;
using System.ComponentModel.DataAnnotations;
namespace MvcAgain.Models {
    public class CarLot {
        [Required]
        public virtual int Id { get; protected set; }
        [StringLength(35), Required]
        public virtual string Name { get; protected set; }
        public virtual ISet Cars { get; protected set; }
    }
}//end of CarLot.cs

Car.hbm.xml and CarLot.hbm.xml

These .hbm.xml files are in the DataAccessLayer project, but they reference the ModelLayer assembly.

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="ModelLayer"
                   namespace="MvcAgain.Models">
  <class name="MvcAgain.Models.Car" lazy="false" table="cars">
    <id name="Id">
      <generator class="native"/>
    </id>
    <property name="Model"/>
    <property name="Manufacturer"/>
    <many-to-one name="Lot" class="CarLot" column="lotid" not-null="true">
    </many-to-one>
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="ModelLayer"
                   namespace="MvcAgain.Models">
  <class name="MvcAgain.Models.CarLot" lazy="false" table="carlots">
    <id name="Id">
      <generator class="native"/>
    </id>
    <property name="Name"/>
    <set name="Cars" inverse="true">
        <key column="lotid"/>
        <one-to-many class="Car"/>
    </set>
  </class>
</hibernate-mapping>

NHibernateSessionFactory.cs (NHibernate configuration code)

using NHibernate.Cfg;
using NHibernate;
namespace MvcAgain.DataAccessLayer {

    public class NHibernateSessionFactory {

        private static ISessionFactory sessionFactory = null;

        private static ISessionFactory SessionFactory {
            get {
                if(sessionFactory == null) {
                    Configuration configuration = new Configuration();
                    configuration.Configure();
                    //note: you must use the name of the assembly
                    //that contains the .hbm.xml mapping files.
                    //For this example NHibernate will load all .hbm.xml files it
                    //finds in the DataAccessLayer assembly
                    configuration.AddAssembly("DataAccessLayer");
                    sessionFactory = configuration.BuildSessionFactory();
                }
                return sessionFactory;
            }
        }

        public static ISession OpenSession() {
            return SessionFactory.OpenSession();
        }
    }//end of class
}//end of namespace

ModelLayer assembly name in the properties pane.

Related Posts

• NHibernate in Action – Book Review
• NHibernate 2 Beginner’s Guide – Book Review
• ASP.Net MVC Book Review and musings

Comments

• 
  
Subscribe:
Feed
Email

• Recently Written

  • .Net Data Provider Overview
  • Strange Loop 2010 – Early Bird Registration
  • NHibernate 2 Beginner’s Guide – Book Review
  • Managing Unmapped Tables with Hibernate
  • If You Want to Have Cities You’ve Got to Build Roads
  • Outliers – A non technical book every freelancer/developer should read
  • Software Review: ForeUI Prototyping Tool
  • Strange Loop 2009 – Day 2
  • Strange Loop 2009 – Day 1
  • NHibernate in Action – Book Review

• Categories

  • .Net
  • Books
  • java
  • open source
  • php
  • Software Tools
  • Uncategorized