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Mapping with a composite-id

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willbarker

Post subject: Mapping with a composite-id

Posted: Tue Feb 05, 2008 8:35 am

Newbie

Joined: Mon Feb 04, 2008 7:42 am
Posts: 7

I am trying to map a many-to-many relationship where the join table has extra fields. I am trying to follow the hibernate best practises and use two one-to-many associations to an intermediate link class.

The DB setup is:
Hotel: PK=(hotl_id)
Language Data: PK=(hld_hotl_id, hld_lang_id), + extra fields
Language: PK=(lang_id)

Hibernate version: 3.2.5

Mapping documents:

So far I have the following mapping. I would be grateful if someone could help with the mapping I should add to the Hotel.hbm.xml mapping.

LanguageData

Code:

<hibernate-mapping>
   <class name="core.languagedata.LanguageData" table="HTL_LANGUAGE_DATA" lazy="false">
      <composite-id name="id" class="core.languagedata.LanguageDataId">
         <key-property name="hotelId" column="HLD_HOTL_ID"/>
         <key-property name="languageId" column="HLD_LANG_ID"/>
      </composite-id>
      <property name="name" column="HLD_NAME" type="java.lang.String" />
      <property name="description" column="HLD_DESCRIPTION" type="java.lang.String" />
      <!--  many-to-one unidirectional association -->
      <many-to-one name="language" column="HLD_LANG_ID" insert="false" update="false"/>
   </class>
</hibernate-mapping>

Language

Code:

<hibernate-mapping>
   <class name="core.language.Language" table="REF_LANGUAGES">
      <id name="id" column="LANG_ID">
         <generator class="assigned" />
      </id>
      <property name="description" column="LANG_DESCRIPTION" type="java.lang.String" />
   </class>
</hibernate-mapping>

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farzad

Post subject: Re: Mapping with a composite-id

Posted: Tue Feb 05, 2008 12:16 pm

Expert

Joined: Wed Apr 11, 2007 11:39 am
Posts: 735
Location: Montreal, QC

What I personally like to do is to give the relationship table its own primary key and do the mapping as below:

Code:

<hibernate-mapping>
   <class name="core.languagedata.LanguageData" table="HTL_LANGUAGE_DATA" lazy="false">
      <id name="id" column="id"..../>
      <property name="name" column="HLD_NAME" type="java.lang.String" />
      <property name="description" column="HLD_DESCRIPTION" type="java.lang.String" />

      <many-to-one name="language" column="HLD_LANG_ID" />
      <many-to-one name="hotel" column="HLD_HOTL_ID" />
   </class>
</hibernate-mapping>

and for both language and hotel you will have a one-to-many to LanguageData:

Code:

....
 <set name="languageData" table="xyz" ...>
     <key column="HLD_LANG_ID"/>
    <one-to-many class="LanguageData" .../>
</set>

However, if you have to keep teh relationship table's schema as it is then you might want to use <key-many-to-one name="propertyName class="ClassName" column="column_name"/>:

Code:

<hibernate-mapping>
   <class name="core.languagedata.LanguageData" table="HTL_LANGUAGE_DATA" lazy="false">
      <composite-id>
         <key-many-to-one name="language" class="Language" column="HLD_LANG_ID"/>        
         <key-many-to-one name="hotel" class="Hotel" column="HLD_HOTL_ID"/>
      </composite-id>
      <property name="name" column="HLD_NAME" type="java.lang.String" />
      <property name="description" column="HLD_DESCRIPTION" type="java.lang.String" />     
   </class>
</hibernate-mapping>

and the many-to-one sides on both Hotel and Language stays the same.

Farzad-

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