This one time, at band camp, Helmut Meisel said:
HM>Hi,
HM>
HM>when I want to retrieve an object from the database that has got a
HM>many-to-many relationship to another object of the same type I get the
HM>following exception:
HM>
HM>org.exolab.castor.jdo.TransactionAbortedException: Nested error:
HM>org.exolab.castor.jdo.PersistenceException: The identity of a data object
HM>of type castortest.data.Entity, has been changed from 2 to 0 since it is
HM>loaded/create/update.
HM>
HM>This is the code I am executing:
HM>
HM> //create test data
HM> Entity child = new Entity(1, "CubanCigar");
HM> Entity parent = new Entity(2, "Cigar");
HM> //create link (method creates child-link as well)
HM> child.addParentEntity(parent);
HM> db.begin();
HM> db.create(parent);
HM> db.create(child);
HM> db.commit();
HM>
HM> //re-read data
HM> db.begin();
HM> Entity cigar = (Entity) db.load( Entity.class, new Integer( 2 ));
HM> db.commit();
HM>
HM>The corresponding Mapping file is:
HM>
HM><?xml version="1.0"?>
HM><mapping>
HM> <description>TestMapping for EntityTest</description>
HM> <class name="castortest.data.Entity" identity="id">
HM> <map-to table="entity" xml="Entity"/>
HM> <!-- id -->
HM> <field name="id" type="integer">
HM> <bind-xml name="identifier"/>
HM> <sql name="id" type="integer"/>
HM> </field>
HM> <!-- name -->
HM> <field name="name" type="string">
HM> <sql name="name"/>
HM> </field>
HM> <!-- Vector parentEntities-->
HM> <field name="parentEntities"
HM> type="castortest.data.Entity" collection="vector">
HM> <bind-xml name="Parent" node="element"/>
HM> <!-- parent relationship -->
HM> <sql many-table="entityparent_rel"
HM> many-key="parentid" name="childid"/>
HM> </field>
HM> <!-- Vector childEntities-->
HM> <field name="childEntities"
HM> type="castortest.data.Entity" collection="vector">
HM> <bind-xml name="Child" node="element"/>
HM> <!-- child relationship -->
HM> <sql many-table="entityparent_rel"
HM> many-key="childid" name="parentid"/>
HM> </field>
HM> </class>
HM></mapping>
HM>
HM>Does anybody know what I am doing wrong?
Helmut,
I noticed that you're mapping an object of type Entity to an object
of type Entity. This is known as a self relation. Castor does not
provide the ability for self relations (i.e. relating two objects
of the same type).
I don't believe that this is the cause of the exception you're
getting, but I'm trying to save you some time. You might spend a
long time trying to chase down this exception only to find that
ultimately, Castor cannot provide what you're trying to do.
Bruce
--
perl -e 'print unpack("u30","<0G)U8V4\@4VYY9&5R\"F9E<G)E=\$\!F<FEI+F-O;0\`\`");'
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