Several classes on same table in same Session

mogadanez · **Joined:** Thu Jun 22, 2006 12:51 pm **Posts:** 10

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Hibernate version: nHibernate 1.2.0.GA

Mapping documents:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false">
  <class name="NHibernate.Test.SomeClassesOnTable.SomeClassesOnTableDigest, NHibernate.Test" table="SomeClassesOnTable">
    <id name="identifier" access="field" column="identifier" unsaved-value="-1" type="string" >
      <generator class="assigned" />
    </id>    
  </class>
</hibernate-mapping>

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" default-lazy="false">

Code:

  <class name="NHibernate.Test.SomeClassesOnTable.SomeClassesOnTableEntity, NHibernate.Test" table="SomeClassesOnTable">
    <id name="identifier" access="field" column="identifier" unsaved-value="-1" type="string" >
      <generator class="assigned" />
    </id>
    <property name="data" type="BinaryBlob" access="field" />
  </class>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():

Code:

  [Test]
        public void Test()
            {
            using ( ISession s1 = OpenSession() )
                {
                ITransaction t1 = s1.BeginTransaction();
                SomeClassesOnTableDigest sb = s1.Get<SomeClassesOnTableDigest>("aaa"); //SessionImpl.nonExists collection now have EntityKey with SomeClassesOnTableDigest  type
                if ( sb == null )
                    {
                        SomeClassesOnTableEntity sb1 = s1.Get<SomeClassesOnTableEntity>("aaa");  //SessionImpl.nonExists collection now have EntityKey with SomeClassesOnTableEntity type
                    Assert.IsNull( sb1 );
                    sb1 = new SomeClassesOnTableEntity("aaa", new byte[] { 1, 2, 3, 4, 5 }); //SessionImpl.nonExists collection remove EntityKey with SomeClassesOnTableEntity type
                    s1.Save( sb1 );
                    }
                SomeClassesOnTableDigest result = s1.Get<SomeClassesOnTableDigest>("aaa");
                Assert.IsNotNull( result, "SessionImpl.nonExists collection still contains EntityKey with SomeClassesOnTableDigest  type. ");
                t1.Rollback();
                s1.Close();
                }
            }

Name and version of the database you are using: MSSQL 2005

Does this case supported?
If not, what is alternative? need need have something like lazy property, that have BIG binary data, and not want load it before it really need.

[/code]

PeteWeissbrod · **Joined:** Tue Sep 04, 2007 12:36 pm **Posts:** 23

Perhaps this is obvious but I wanted to make sure.

Is it OK to separate the BLOB in to a separate table with a many-to-one reference on the "Digest" table?

This way, the "Digest" object could lazily load the BLOB in a simple manner.

Another way would be the component mapping feature, where the blob is a component of the digest object
http://www.hibernate.org/hib_docs/nhibernate/html/components.html

Finally, Ayende has a solution for lazy property loading, but it is somewhat new:
http://www.ayende.com/Blog/archive/2007/08/26/Lazy-Property-Loading-In-NHibernate.aspx

I dont know if this makes your design ugly, but these options have potential to solve your problem in a simple way.[/url]