I have two tables A and B. B is child table of A.
A have Primary Key and a seq assigned to it. B have a Primary key and seq assigned to it and alo FK which is the PK in Table A.

For table A I need to insert a PK value So I used <generator class="assigned" />

But for table B System has to assign a uniqID as PK Then what is my generater class value in the mapping file ?

Thanks in advance for the clarification

Sudhakar

This is more of a database design question than Hibernate question.
You wrote that table B was a child of table A. I'm assuming you're talking about many-to-one relationship (many B records link to a single A record).
If this is the case, then your problem is how to generate the A key, not the B key, since B simply references A key. Either way, I would suggest using sequence generators (for both tables) if your database supports it. If you don't know what it is, talk to your DBA.
This is example hbm mapping for table A (for Oracle db):

<class name="ClassA" table="TABLE_A" schema="MY_SCHEMA" lazy="true">

<!-- primary key -->
<id name="aId" type="long">
<column name="TABLE_A_ID" precision="10" scale="0" />
<generator class="sequence">
<param name="sequence">seq_table_a_id</param>
</generator>
</id>

<!-- example property -->
<property name="xxx" type="xxx">
<column name="xxx" precision="10" scale="0" />
</property>

<!-- collection of children records -->
<set name="bRecords" inverse="true" lazy="true">
<key>
<column name="TABLE_A_ID" precision="10" scale="0" />
</key>
<one-to-many class="ClassB" />
</set>

</class>
</hibernate-mapping>

"seq_table_a_id" is the name of the sequence generator that will give you new values for table_a_id (this needs to be created in the database).

This is example hbm mapping for table B:

<class name="ClassB" table="TABLE_B" schema="MY_SCHEMA" lazy="true">

<!-- primary key -->
<id name="bId" type="long">
<column name="TABLE_B_ID" precision="10" scale="0" />
<generator class="sequence">
<param name="sequence">seq_table_b_id</param>
</generator>
</id>

<!-- link to parent record (reference) -->
<many-to-one name="aRecord" class="ClassA" fetch="select">
<column name="TABLE_A_ID" precision="10" scale="0" />
</many-to-one>

<!-- example property -->
<property name="yyy" type="string">
<column name="yyy" length="20" />
</property>

</class>
</hibernate-mapping>

HTH,

Bratek

PS. If you really have to insert a value for primary key, for example you have an algorithm that generates those keys for you, then just change generator class to assigned for ClassA. It would still be a good idea to use sequence generators for ClassB.

Bratek

Depending on your database there are different generators. increment, sequence, ...
Please look for this in the Reference, Wiki or FAQ. I am sure it is there.
google for hibernate mydatabase generator could also help.

Regards Sebastian

Thank you so much for your quick repply. I am using Oracle database and both tables have defined a sequence for primary Key.And I came to know I don not insert any value for this primaryky for any of the tables. "bratek" is right and he has given example I think I can just use it as it is without any changes.

correct ?

Thanks

BTW I am using the middle gen tool to generate mapping files. Can I just use as it is or should I do any modifications for this relation of tables

I would check the id elements of each class. In my case after importing mappings from an existing schema generator property was set by default to assign. You might need to change it to sequence.

Bratek

You are right. Middle gen identified generator and showing a dropdown to select sequence for some table and not for other tables even it has defined a sequnce for the primary key. I will have to manually modify those mapping files generator as sequence.

Thanks

I am a new user and if I am trying to post new thread, it is displaying a message saying I need atleast 1 credit to post a new topic. How can a new user can get a credit when he does not have a knowledge to answer any hibernate questions.

Thanks

It seems to me I have consumed all my intial 10 credits. Beacuse of this reson I am posting a new question in my old thread. I want to lern about all attributes and their usage in mapping.hbm.xml file. Where can I find?

Example: cascade,lazy, inverse ...etc.

Thanks

The Online Reference at
http://www.hibernate.org/hib_docs/v3/re ... ml_single/
has all the things required to start doing work with Hibernate. Hibernate in Action is also a good reference. Go through the online reference (and the tutorial that comes with it). That should be a good start!

Good luck :)