This one time, at band camp, Orjan Palsson said:
OP>
OP>I would like to make a many to many relation with a role classifier on
OP>the relation. Is it possible with Castor JDO? In that case - how? I have
OP>checked the JDO examples and the test cases, and there are only normal
OP>many-many relations without role classifier.
OP>
OP>/ Orjan
OP>
OP>Below is an example of the mapping file and the corresponding tables:
OP>
OP><mapping>
OP>
OP> <key-generator name="MAX" alias="normal">
OP> </key-generator>
OP>
OP> <class name="Station"
OP> identity="id" key-generator="normal">
OP> <description>A station participating in a session</description>
OP> <map-to table="Station" />
OP> <field name="id" type="integer" >
OP> <sql name="stationId" type="integer"/>
OP> </field>
OP> <field name="name" type="string">
OP> <sql name="name" type="varchar" />
OP> </field>
OP> </class>
OP>
OP> <class name="Session"
OP> identity="id" key-generator="normal">
OP> <description>A send/receive session</description>
OP> <map-to table="Session" />
OP> <field name="id" type="integer" >
OP> <sql name="sessionId" type="integer"/>
OP> </field>
OP> <field name="name" type="string">
OP> <sql name="name" type="varchar" />
OP> </field>
OP> <field name="participants" type="Station"
OP> collection="vector">
OP> <sql name="stationId"
OP> many-table="Participant" many-key="sessionId"/>
OP> </field>
OP> </class>
OP>
OP></mapping>
OP>
OP>Create table Session (
OP> sessionId Int NOT NULL ,
OP> name Varchar(20) ,
OP> UNIQUE (sessionId),
OP> Primary Key (sessionId));
OP>
OP>Create table Station (
OP> stationId Int NOT NULL ,
OP> name Varchar(20),
OP> UNIQUE (stationId),
OP> Primary Key (stationId));
OP>
OP>Create table Participant (
OP> role Char(5) NOT NULL , // SEND, RECEIVE, etc.
OP> stationId Int NOT NULL ,
OP> sessionId Int NOT NULL ,
OP> Primary Key (stationId,sessionId));
Orjan,
The JDO examples provide an example of a many-to-many mapping between
Product and Category. Is this not sufficent? However, seeing the
DDL above, I don't see how Participant.role would be a many-to-many?
Can you explain further what you want to do?
Bruce
--
perl -e 'print unpack("u30","<0G)U8V4\@4VYY9&5R\"F9E<G)E=\$\!F<FEI+F-O;0\`\`");'
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