idbag collection mapping - surrogate key question

jhg · **Joined:** Mon Oct 23, 2006 11:03 pm **Posts:** 17

On page 254 of JPWH is an example of a collection mapped as an
<idbag> with a surrogate key declared as a <collection-id>.

My question has to do with the definition of the Java class corresponding
to the <composite-element> class. Does the Java class contain a property
for the collection-id (in the example "ITEM_IMAGE_ID")?

If not, does that mean that the Java class cannot (should not?) be aware
of its surrogate key, and the surrogate key is not retrievable in Java?

The reason for this question is that I implemented this pattern with
getter/setter methods for the surrogate key in the Java class, but
the setter method is not being called when Hibernate loads the collection
from the database. The debug log shows that the column is being
fetched but its value is not being placed into the Java object.

jhg · **Joined:** Mon Oct 23, 2006 11:03 pm **Posts:** 17

I tried just adding the column to the composite-element. See below,
the "PROJECT_ID" column inside the <composite-element> tag inside
the <idbag> tag.

Unfortunately, Hibernate doesn't like the fact that the PROJECT_ID
column is now mapped twice, once as the collection-id, and once as
an attribute. The exception is

org.hibernate.MappingException: Repeated column in mapping for collection: com.wholefoods.ittoolkit.ws.admin.Team.projects column: PROJECT_ID

I tried adding a 'name=' attribute to the <collection-id> but that is
not allowed by the DTD.

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.wholefoods.ittoolkit.ws.admin">
  <class name="Team" table="CR_TEAM">
     <id name="id" column="TEAM_ID">
        <generator class="sequence">
           <param name="sequence">CR_TEAM_ID</param>
        </generator>
     </id>
     <property name="version" column="VERSION"/>
     <property name="name" column="NAME"/>
     <property name="email" column="EMAIL"/>
     <property name="remedyGroupId" column="RMDY_GROUP_ID"/>
     
     <set name="members" table="CR_TEAM_MEMBER">
        <key column="TEAM_ID"/>
        <composite-element class="TeamMember">
           <property name="name"   column="NAME"    not-null="true"/>
           <property name="email"  column="EMAIL"   not-null="true"/>
           <property name="userId" column="USER_ID" not-null="true"/>
           <property name="roleId" column="ROLE_ID" not-null="true"/>
        </composite-element>
     </set>

     <idbag name="projects" table="CR_PROJECT" order-by="NAME asc">
        <collection-id type="long" column="PROJECT_ID">
           <generator class="sequence">
              <param name="sequence">CR_PROJECT_ID</param>
         </generator>
      </collection-id>
      
        <key column="TEAM_ID"/>
        
        <composite-element class="TeamProject">
           <property name="id"     column="PROJECT_ID"/>
           <property name="name"   column="NAME"    not-null="true"/>
        </composite-element>
     </idbag>
     
  </class>
</hibernate-mapping>

christian · **Posted:** Fri Mar 02, 2007 4:44 pm

formula="repeatedcolumn"