I have two table, say table A and table B,
table A has primary key uid (assigned) and B has also primary key
uid (assigned).

The reationship is: if there a row in table B, there is always a row of same
uid in table A. But if there is row in A, the same uid may not exist in table
B

So I have many-to-one mapping as follows (see below).

However, whenver I try get a instance of A using
session.find(), it *ALWAYS* tries to make an instance of B of same
uid. If there is no row exist in table B,
Hibernate throws UnresolvableObjectException.


for table A:

<class
name="A'
table="A"
>
<id
name="uid"
column="uid"
type="java.loang.Long"
<generator class="assigned"
</id>

<many-to-one
name="partner"
column="uid"
update="false"
insert="false"
class="B"
not-null="false"
/>

</class>



for table B:
<class
name="B"
table="B"
>
<id
name="uid"
column="uid"
type="java.loang.Long"
<generator class="assigned"
</id>
</class>

Could you please post the query you are running in the session.find().

The query is like this

session.find("from A as a where a.uid = ?", new Long(332), Hibernate.INTEGER);

I have tested uids that appear in both table without any problem.
The problem happens only when if a uid exists in table A, but not B.

Well the problem is occuring because of the mapping. As you are mapping the primary key column of A as the many-to-one column to B, Hibernate is looking at the results it gets back and basically assuming that there is a partner associated with it, as there is a value in the uid column.

It would be better to map this as the one-to-one mapping it really is, and if you make it bidirectional, you can enforce the rules about a row in B having to have a row in A. The mappings would be as follows:

I got it working. Thank you so much.

Sorry I still have one thing that need help:

How to put these mapping as XDoclet tag in java source code file?
Can you show me how to? or can you give a place that I can examples?

Thanks

In class A, in the JavaDoc above your getter (well that's where I usually put my mappings anyway):



In class B:



Depending upon how you have your configuration set-up, you may well need the full package declared for your classes in those mappings - if hibernatedoclet moans that it can't find the class, that's the problem.

Just as a warning, you should read the document on IDs, as using assigned identifiers changes how you save and update your entities - http://www.hibernate.org/hib_docs/reference/en/html/mapping.html#mapping-declaration-id-assigned.

Thank You!!