Many-To-Many w/ Composite Key

[Russell Ray]

I am hoping someone can guide me through this issue. I have solved this problem earlier using JPA, but I now must use Hibernate only.

This is the annotation I used in JPA.

@ManyToMany(cascade={CascadeType.ALL}) 
      @JoinTable(name="DOCUMENT_COLLECTION", 
                  joinColumns=@JoinColumn(name="DC_DOCUMENT_ID", referencedColumnName="DOCUMENT_ID"), 
                  inverseJoinColumns={@JoinColumn(name="DC_COLLECTION_SITE", referencedColumnName="SITE_ID"), 
                                      @JoinColumn(name="DC_COLLECTION_NAME", referencedColumnName="NAME"), 
                                      @JoinColumn(name="DC_COLLECTION_GROUPDATE", referencedColumnName="GROUP_DATE")} 

The goal is a document may belong to many groups. A group may have many documents. How I handled this using JPA was create a Document_Collection table. I have done the same in Hibernate by creating a table called document_collection_groupXref.

I've tried to follow the "Java Persistence with Hibernate" book in creating my solution. Here are the hibernate files


jtdiDocument.hbm.xml

<hibernate-mapping default-cascade="all"> 
    <class name="jtdi.metadata.orm.JtdiDocument" table="jtdi_document" catalog="jtdi_metadata_db"> 
        <id name="jtdiDocumentId" type="java.lang.Integer"> 
            <column name="jtdi_document_id" /> 
            <generator class="native" /> 
        </id> 
.... 
        
         <set name="documentCollectionGroup" inverse="true"> 
            <key><column name="dc_document_id" not-null="true" /></key> 
            <one-to-many class="jtdi.metadata.orm.DocumentCollectionGroupXref" /> 
        </set> 
        
    </class> 
</hibernate-mapping> 

CollectionGroup.hbm.xml

<hibernate-mapping default-cascade="all"> 
    <class name="jtdi.metadata.orm.CollectionGroup" table="collection_group" catalog="jtdi_metadata_db"> 
    
        <composite-id name="id" class="jtdi.metadata.orm.CollectionGroupId"> 
            <key-property name="siteId" type="java.lang.String"> 
                <column name="site_id" length="50" /> 
            </key-property> 
            <key-property name="groupName" type="java.lang.String"> 
                <column name="group_name" length="50" /> 
            </key-property> 
            <key-property name="groupDate" type="java.lang.String"> 
                <column name="group_date" length="50" /> 
            </key-property> 
        </composite-id> 
        
.... 
        
 
        <set name="documentCollectionGroup" table="document_collection_group_xref"> 
            <key><column name="id" not-null="true" /> </key> 
            <composite-element class="jtdi.metadata.orm.DocumentCollectionGroupXref"> 
                <parent name="CollectionGroup"/> 
                <many-to-one name="JtdiDocument" 
                             column="jtdi_document_id" 
                             not-null="true" 
                             class="jtdi.metadata.orm.JtdiDocument" /> 
            </composite-element> 
        </set> 
    </class> 
</hibernate-mapping> 

Lastly, DocumentCollectionGroupXref.hbm.xml

<hibernate-mapping default-cascade="all"> 
    <class name="jtdi.metadata.orm.DocumentCollectionGroupXref" 
           table="document_collection_group_xref" 
           catalog="jtdi_metadata_db" 
           mutable="false"> 
        
        
        <composite-id name="id" class="jtdi.metadata.orm.DocumentCollectionGroupXrefId"> 
            <key-property name="dcDocumentId" type="java.lang.Integer"> 
                <column name="dc_document_id" /> 
            </key-property> 
            <key-property name="dcCollectionSite" type="java.lang.String"> 
                <column name="dc_collection_site" length="50" /> 
            </key-property> 
            <key-property name="dcCollectionGroupName" type="java.lang.String"> 
                <column name="dc_collection_group_name" length="50" /> 
            </key-property> 
            <key-property name="dcCollectionGroupDate" type="java.lang.String"> 
                <column name="dc_collection_group_date" length="50" /> 
            </key-property> 
        </composite-id> 
        
        <many-to-one name="jtdi_document" 
                     column="jtdi_document_id" 
                     not-null="true" 
                     insert="false" 
                     update="false"/> 
                      
        <many-to-one name="collection_group" 
                     column="id" 
                     not-null="true" 
                     insert="false" 
                     update="false"/> 
                      
                      
    </class> 
</hibernate-mapping> 

I've thoroughly confused myself on how to proceed. In JPA I never had to touch the xref table. All I had to do was add the collection group to the Document class and add the document to the CollectecionGroup Class and JPA would do all the mapping to the cross-reference table.

What the Hibernate book tells me to maintain a Set of DocumentCollectionGroupXref classes in the Document class and in the CollectionGroup Class. However, this approach assumes a Group already exist.

Any counsel would be greatly appreciated.


Russ