In particular, I'd expect
a2 not pointing to b2 anymore, as this clearly is supposed to be is a 1:1
relationship. The implementation can determine this being a 1:1 association, as
there are two corresponding fields, and consequently it should issue
Bu
default, there is no 1:1 relationships either in Java or in RDBMS.
If
you want to insure this 1:1 bi-directional link you have to:
- use some triggers in your db
- use a JDO callback
- do it cleanly in your set /getters in Java
- use an ORM tool that can manage 1:1
bi-directional links
Best
Regards,
....: Eric Samson, Founder &
CTO, xcalia
Service
your Data!
De : Jörg von Frantzius
[mailto:[EMAIL PROTECTED]
Envoyé : mercredi 17 mai 2006
17:40
À : Apache JDO project
Cc : JDO Expert Group
Objet : Setting a 1:1
association with "mapped-by"
Hello JDO experts,
when writing some JUnit test today I came across an interesting phenomenon. I
have two classes A and B with a 1:1 association between them. The FK is put on
class A, and the corresponding field on B has "mapped-by" with the
corresponding field on A (see metadata below).
Now when I have the following object graph:
![]()
and perform the operation
a1.setB_1to1(b2)
then I'd expect the object graph to look like the
following:
![]()
In particular, I'd expect a2 not pointing to b2
anymore, as this clearly is supposed to be is a 1:1 relationship. The
implementation can determine this being a 1:1 association, as there are two
corresponding fields, and consequently it should issue
"UPDATE A SET B_1TO1_FK=NULL WHERE
B_1TO1_FK=2"
before
"UPDATE A SET B_1TO1_FK=2 WHERE ID=1"
to keep this being a 1:1 association.
However, what I end up with in the database is:
![]()
Does this really work as expected?
Here's the metadata:
<class name="A"
identity-type="application" table="A"
detachable="true"
objectid-class="javax.jdo.identity.LongIdentity"
persistence-modifier="persistence-capable">
<inheritance
strategy="new-table"/>
<version
strategy="version-number" column="jdoversion"/>
<field
name="id" primary-key="true"
persistence-modifier="persistent" value-strategy="sequence"
sequence="A_SEQ" >
<extension vendor-name="jpox" key="key-database-cache-size"
value="100"/>
</field>
<field name="b_1to1" column="b_1to1_FK"
persistence-modifier="persistent" >
</field>
</class>
<class name="B" identity-type="application"
table="B" detachable="true"
objectid-class="javax.jdo.identity.LongIdentity"
persistence-modifier="persistence-capable">
<inheritance
strategy="new-table"/>
<version
strategy="version-number" column="jdoversion"/>
<field
name="id" primary-key="true"
persistence-modifier="persistent" value-strategy="sequence"
sequence="B_SEQ" >
<extension vendor-name="jpox"
key="key-database-cache-size" value="100"/>
</field>
<field name="a_1to1" mapped-by="b_1to1"
persistence-modifier="persistent" >
</field>
</class>
Regards,
Jörg
P.S.
I hope the pictures survived...
