NHibernate Many-to-Many Mapping not working

I have a Nhibernate mapping file for a simple user/role mapping.

Here are the mapping files:

Users.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Sample.Persistence" namespace="Sample.Persistence.Model">
    <class name="User" table="Users">
        <id name="UserKey">
            <generator class="identity"/>
        </id>

        <property name="UserName" column="UserName" type="String" />
        <property name="Password" column="Password" type="Byte[]" />

        <property name="FirstName" column="FirstName" type="String" />
        <property name="LastName" column="LastName" type="String" />
    开发者_Python百科    <property name="Email" column="Email" type="String" />

        <property name="Active" column="Active" type="Boolean" />
        <property name="Locked" column="Locked" type="Boolean" />

        <property name="LoginFailures" column="LoginFailures" type="int" />
        <property name="LockoutDate" column="LockoutDate" type="DateTime" generated="insert" />

        <property name="Expired" column="Expired" type="Boolean" generated="insert"/>

        <set name="Roles" table="UsersRolesBridge"   lazy="false">
            <key column="UserKey" />
            <many-to-many class="Role"
            not-found="exception"
            column="RoleKey" />
        </set>

    </class>
</hibernate-mapping>

Role.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Sample.Persistence" namespace="Sample.Persistence.Model">
    <class name="Role" table="Roles">
        <id name="RoleKey">
            <generator class="identity"/>
        </id>
        <property name="Name" column="Name" type="String" />

        <set name="Users" inverse="true" table="UsersRolesBridge" lazy="false" >
            <key column="RoleKey" />
            <many-to-many class="User" column="UserKey" />
        </set>
    </class>
</hibernate-mapping>

I am able to retrieve roles for each user via NHibernate but when I go to save a new object, the roles are not saved in the Bridge table.

The user is created and insert with no issues. I've checked that the Role collection, a field on the user, is being populated with the proper rolekey before the Session.Save() is called.

There is no exception thrown as well.

UPDATE:

After adding a cascade, there was still no actual insert taking place to the M-2-M table.

The logs from Nhibernate showed the following:

12/22/2010 23:18:11.684 [11] INFO  NHibernate.Engine.Cascade 
Message: processing cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for: Sample.Persistence.Model.User
Exception: 

12/22/2010 23:18:11.686 [11] INFO  NHibernate.Engine.Cascade 
Message: done processing cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for: Sample.Persistence.Model.User
Exception: 

12/22/2010 23:18:11.789 [11] INFO  NHibernate.Engine.Cascade 
Message: processing cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for: Sample.Persistence.Model.User
Exception: 

12/22/2010 23:18:11.792 [11] INFO  NHibernate.Engine.Cascade 
Message: cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for collection: Sample.Persistence.Model.User.Roles
Exception: 

12/22/2010 23:18:11.814 [11] INFO  NHibernate.Engine.Cascade 
Message: done cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for collection: Sample.Persistence.Model.User.Roles
Exception: 

12/22/2010 23:18:11.814 [11] INFO  NHibernate.Engine.Cascade 
Message: done processing cascade NHibernate.Engine.CascadingAction+SaveUpdateCascadingAction for: Sample.Persistence.Model.User

You haven't specified a cascade on the relationship. By default, inserts, updates, and deletes are not cascaded. More information here:

http://ayende.com/Blog/archive/2006/12/02/nhibernatecascadesthedifferentbetweenallalldeleteorphansandsaveupdate.aspx

I generally find that many to many issues are caused by not setting the cascade properties properly.

Try setting the cascade = "save-update" attribute on the Roles set in the Users.hbm.xml file

<set name="Roles" table="UsersRolesBridge"   lazy="false" cascade="save-update">