In a Person class, i have id property for natural id which is primary key. Then i have two more fields, subject and year. How to specify both of them as UNIQUE key. So in database, combination of (subject, year) should be unique and id is the primary key.

class Person{
private Long id;
private String subject;
private int year;
}


I am looking for simple solution instead of writing a PersonId class for composite key.

Thanks

As annotations:


As xml:

Mike,
Thanks for your reply. It has partially solved my problem. Here is my actual POJO:

class Person{
private Long id;
private Subject subject; //subject
private Batch batch; //student batch
//other properties
}

I want to make Subject, Batch as UNIQUE key. Also I am using xdoclet2 to genernate the hbm.

In Person.hbm.xml as the Subject and Batch has many-to-one relation, there is a properties-name tag. But when I add, all the properties of the Person classes are added between properties tag.

So I am adding my <properties> tag after generating the hbm.
Do you have any idea how to fix this problem in xdoclet2?

Thanks
Shyam

Saw the following on the net... should work for you.

Mike,
I have already tried that solution with XDoclet. And my xdoclet parser is generating a invalid hbm file. Then I referred to hibernate-mapping-3.0.dtd
http://hibernate.sourceforge.net/hibern ... ng-3.0.dtd
It has the following defination for properties
*******************************************
<!-- properties declares that the contained properties form an alternate key. The name
attribute allows an alternate key to be used as the target of a property-ref. -->

<!ELEMENT properties (
(property|many-to-one|component|dynamic-component)*
)>
<!ATTLIST properties name CDATA #REQUIRED>
<!ATTLIST properties unique (true|false) "false">
<!ATTLIST properties insert (true|false) "true">
<!ATTLIST properties update (true|false) "true">
<!ATTLIST properties optimistic-lock (true|false) "true">
<!ATTLIST properties node CDATA #IMPLIED>
**************************************************

And here what I have to write in Person.hbm.xml

<properties name="subject_batch_unique" unique="true">
<many-to-one
name="subject"
not-null="true"
cascade="save-update"
lazy="false"
>
</many-to-one>

<many-to-one
name="batch"
not-null="true"
>
</properties>

So after generating my hbm using xdoclet, I have to add the above text for properties. I wish xdoclet could have parsed this properly.

P.S. It is always better to refer to the hibernate-mapping-xxx.xx.dtd to resolve the issues. We can't trust the tools like xdoclet as it not fully mature and well developed.

Thanks
Shyam