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Re: [eclipselink-users] inheritance with TABLE_PER_CLASS
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Hi Markus,
Table per class inheritance is available as an optional feature in the
specification.
EclipseLink provides some basic support based on what is described in the
specification.
The following wiki page is from our design cycle and points out some current
limitations:
http://wiki.eclipse.org/EclipseLink/Development/JPA_1.0/table_per_class
Are you having specific issues? If so, this list is a good place to discuss
them. Also, if you are encountering bugs related to the limitations, please
have a look through bugzilla and vote for any bugs that are issues for you, or
file your own.
-Tom
Hahn, Markus wrote:
Hi,
i want to use inheritance for a hierarchy where the base class contains
ALL attributes and the 2 subclasses none. But the subclasses are mapped
to different database tables.
I know that polymorphic associations are not possible in JPA 1.0 but are
there ways to capture this scenario in EL?
Below an xml snippet:
Base class:
<orm:entity class="ChangeTrackingExportEntryBase">
<orm:inheritance strategy="TABLE_PER_CLASS"/>
<orm:attributes>
<orm:id name="id">
<orm:column column-definition="decimal" length="18" name="ID"/>
<orm:generated-value generator="SeqChangeTrackingExportEntry"/>
</orm:id>
<orm:basic name="attributeName">
<orm:column length="128" name="ATTRIBUTENAME" nullable="true"/>
</orm:basic>
<orm:basic name="domainObjectName">
<orm:column length="1000" name="DOMAINOBJECTNAME" nullable="true"/>
</orm:basic>
<orm:basic name="acknowledged">
<orm:column name="ACKNOWLEDGEDATE" nullable="true"/>
</orm:basic>
<orm:basic name="exported">
<orm:column name="EXPORTDATE" nullable="true"/>
</orm:basic>
<orm:basic name="created">
<orm:column name="TSCREATE" nullable="false"/>
</orm:basic>
<orm:basic name="objectId">
<orm:column column-definition="decimal" length="10"
name="DOMAINOBJECTENTRYID" nullable="false"/>
</orm:basic>
<orm:version name="versionTimestamp">
<orm:column name="TSUPDATE" nullable="false"/>
</orm:version>
<orm:many-to-one name="company" fetch="LAZY">
<orm:join-column column-definition="decimal" length="18"
name="ID_COMPANY" nullable="true"/>
<orm:cascade>
<orm:cascade-merge/>
</orm:cascade>
</orm:many-to-one>
<orm:many-to-one name="changeExportRegistration" fetch="LAZY">
<orm:join-column column-definition="decimal" length="18"
name="ID_CHANGEEXPORTREGISTRATION" nullable="false"/>
<orm:cascade>
<orm:cascade-persist/>
<orm:cascade-merge/>
</orm:cascade>
</orm:many-to-one>
<orm:many-to-many name="changeTrackingLogEntries"
mapped-by="changeTrackingExportEntries">
<orm:cascade>
<orm:cascade-persist/>
<orm:cascade-merge/>
</orm:cascade>
</orm:many-to-many>
<orm:many-to-one name="confirmedState" fetch="LAZY">
<orm:join-column column-definition="decimal"
name="ID_CONFIRMEDSTATE" nullable="true"/>
<orm:cascade>
<orm:cascade-merge/>
</orm:cascade>
</orm:many-to-one>
</orm:attributes>
</orm:entity>
The subclasses:
<orm:entity class="ChangeTrackingExportEntry">
<orm:table name="BUYING.CHANGETRACKINGEXPORTENTRY"/>
</orm:entity>
<orm:entity class="ChangeTrackingExportEntryHistory">
<orm:table name="BUYING.CHANGETRACKINGEEHIST"/>
</orm:entity>
Regards, Markus
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