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Fluent NHibernate table per hierarchy mapping problem

Answer 1

A:

I found here that there is a bug related to this situation. I tried in code using (int)1, but it still fails. Still, this guy here shows us an example of table per class hierarchy example. His mapping is similar, his generated hbm file is compatible...

DaeMoohn 2009-08-28 08:56:26

I figured it out. Stop using DiscriminateSubClassesOnColumn<int>("ActivityType"), use instead DiscriminateSubClassesOnColumn("ActivityType"). And I also found out how to specify discriminator value in subclass: DiscriminatorValue(1). It's closed, I guess.

DaeMoohn 2009-08-28 09:28:20

Answer 2

A:

Did you figure it out how to use enums instead of integers? With integers it works like you described but with enums it does not. Not even if I cast them to int

E.g. DiscriminatorValue((int)SomeEnum.SomeVaue))

Anonymous 2009-08-28 10:22:17

No, i didn't. Please look at http://code.google.com/p/fluent-nhibernate/issues/detail?id=240 , it's an open issue, and I've placed a question there too. Look here too: http://groups.google.com/group/fluent-nhibernate/browse_thread/thread/4d38111df91e72b9 . I use the integer just like an enumeration, maybe I'll adopt it soon.

DaeMoohn 2009-08-28 11:07:13

As soon as I'll have a concept working, I'll try with an enum too and I'll give you an answer.

DaeMoohn 2009-08-28 11:13:38

Answer 3

+2 A:

I figured it out in case of enums.

Considering this enum type:

public enum ActivityType
{
    [EnumKey("1")]
    [EnumDescription("ImportFromFile")]
    ImportFromFile,
}

where EnumKey and EnumDescription are (popular) extension methods, I redefine Activity like

public abstract class Activity
    {
        public virtual Guid Id { get; set; }
        public virtual ActivityExecutionResult ExecutionResult { get; private set; }

        public virtual ActivityExecutionStatus ExecutionStatus {get;private set;}

        public abstract ActivityExecutionStatus Execute();

        public virtual string ActivityName { get; private set; }

        public virtual IDictionary<string, string> ActivityParameters { get; private set; }

        public virtual ActivityType ActivityType { get; private set; }
    }

The mapping file looks like this:

public class ActivityMap : ClassMap<Activity>
    {
        public ActivityMap()
        {
            Table("Activities");
            Id(x => x.Id).Column("ID").GeneratedBy.Guid();
            Map(x => x.ActivityName).Not.Nullable().Length(50);
            Map(x => x.ActivityType).CustomType<int>().Column("ActivityType").Not.Nullable();
            HasMany(x => x.ActivityParameters)
                .KeyColumn("ActivityID")
                .AsMap<string>(idx => idx.Column("ParameterName"), elem => elem.Column("ParameterValue"))
                .Not.LazyLoad()
                .Cascade.Delete()
                .Table("ActivityParameters");

            DiscriminateSubClassesOnColumn("ActivityType");
        }
    }

    public class ImportActivityFromFileMap : SubclassMap<ImportActivityFromFile>
    {
        public ImportActivityFromFileMap()
        {
            DiscriminatorValue(ActivityType.ImportFromFile.GetKey());
        }
    }

The generated hbm file looks like:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-access="property" auto-import="true" default-cascade="none" default-lazy="true">
  <class xmlns="urn:nhibernate-mapping-2.2" name="***.Activity, ***, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" table="Activities">
    <id name="Id" type="System.Guid, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="ID" />
      <generator class="guid" />
    </id>
    <discriminator column="ActivityType" type="String" insert="true" not-null="true" />
    <property name="ActivityName" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
      <column name="ActivityName" length="50" not-null="true" />
    </property>
    <property name="ActivityType" type="Int32">
      <column name="ActivityType" not-null="true" />
    </property>
    <map cascade="delete" lazy="false" name="ActivityParameters" table="ActivityParameters">
      <key>
        <column name="ActivityID" />
      </key>
      <index type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <column name="ParameterName" />
      </index>
      <element type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
        <column name="ParameterValue" />
      </element>
    </map>
    <subclass name="***.ImportActivityFromFile, ***, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" discriminator-value="1" />
  </class>
</hibernate-mapping>

It works like a charm!

DaeMoohn 2009-08-28 13:29:50

Please note that this is no longer considered a bug by the Fluent NHibernate development team. Please read this comment: http://code.google.com/p/fluent-nhibernate/issues/detail?id=240#c10 .

DaeMoohn 2009-08-29 19:57:53

Answer 4

A:

I'll show another implementation that I came up with.

public class SmartEnumMapping<T> : IUserType
    {
        #region IUserType Members

        public object Assemble(object cached, object owner)
        {
            return cached;
        }

        public object DeepCopy(object value)
        {
            return value;
        }

        public object Disassemble(object value)
        {
            return value;
        }

        public int GetHashCode(object x)
        {
            return x.GetHashCode();
        }

        public bool IsMutable
        {
            get { return false; }
        }

        public new bool Equals(object x, object y)
        {
            return object.Equals(x, y);
        }

        public object NullSafeGet(System.Data.IDataReader rs, string[] names, object owner)
        {
            int index0 = rs.GetOrdinal(names[0]);
            if (rs.IsDBNull(index0))
            {
                return null;
            }
            string key = rs.GetString(index0);
            return EnumExtensions.EnumParseKey<T>(key, false, true);
        }

        public void NullSafeSet(System.Data.IDbCommand cmd, object value, int index)
        {
            if (value == null)
            {
                ((IDbDataParameter)cmd.Parameters[index]).Value = DBNull.Value;
            }
            else
            {
                T enumValue = (T)Enum.Parse(typeof(T), value.ToString());
                ((IDbDataParameter)cmd.Parameters[index]).Value = enumValue.GetKey();
            }
        }

        public object Replace(object original, object target, object owner)
        {
            return original;
        }

        public Type ReturnedType
        {
            get { return typeof(T); }
        }

        public global::NHibernate.SqlTypes.SqlType[] SqlTypes
        {
            get { return new SqlType[] { SqlTypeFactory.GetString(4096) }; }
        }

        #endregion
}

With this, the mapping becomes

Map(x => x.ActivityType).CustomType<SmartEnumMapping<ActivityType>>().Column("ActivityType").Not.Nullable();

ActivityType looks like

public enum ActivityType
    {
        [EnumKey("1")]
        [EnumDescription("dada")]
        dad,

        [EnumKey("2")]
        [EnumDescription("da")]
        ImportCalculAtasateSfarsitLuna,

        [EnumKey("3")]
        [EnumDescription("da")]
        das,

        }

With this, in code i can use "ActivityType.das", but when persisting, it is persisted "3". Again, when reading from database, I read "3", but I'll transform that into "ActivityType.das".

I guess this is a more appropriate answer that explains the behaviour mentioned in the preceding answer.

Once again, the EnumKey, EnumDescription, EnumParseKey etc. are stuff that can be easily found on the internet.

DaeMoohn 2009-09-17 04:48:02

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Fluent NHibernate table per hierarchy mapping problem

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