How is the following one-to-many relationship mapped in Hibernate?

For example, suppose we have two entities: a US_State entity with attributes abbreviation and name, with abbreviation being a key, and an Address entity with attributes street, city, zip and state_abbrev. With the restriction that every state_abbrev value occurs as a value of abbreviation in some US_State instance, we have a one-to-many relationship from US_State to Address (See figure.) http://www2002.org/CDROM/alternate/698/

dekalaked,

What you have there are two tables defined as follows:
(MySQL Code used to demonstrate)



Given the following SQL snippet what you have is a many-to-one relationship between the Address tables state_abbrev and the US_State tables abbreviation field therefore you can map it in hibernate like so:



Most (note: I said MOST) one-to-many mappings can also be thought of as many-to-one mappings.

I hope this clarifies things for you!

------------------------------------------------
Nathan

Hibernate seems to want to update the US_State table when the Address table is updated. Can Hibernate be configured to not update thet US_State table?

dekalaked,

Hibernate will only update the US_State table when the instance of an Address object that you are persisting has a US_State object attached to the getStateAbbrev() field that is not in the database already.

It would be helpful if you could post some code snippets of where you are creating your objects and where you are persisting them.

Also, some snippets of your mapping files and actual object construction would be helpful also.

-----------------------------------------------
Nathan

Here are two mappings: Property and Office.
This works: <many-to-one name="office" class="Office" column="office_id" cascade="none" />
The error below is generated if cascade="none" is removed from
<many-to-one name="office" class="Office" column="office_id" />

21:51:26,453 DEBUG DefaultFlushEntityEventListener:229 - Updating entity: [domain.Property#2]
21:51:26,468 DEBUG DefaultFlushEntityEventListener:229 - Updating entity: [domain.Office#1]
21:51:26,468 WARN RequestProcessor:528 - Unhandled Exception thrown: class org.hibernate.PropertyValueException

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping
default-cascade="save-update"
auto-import="true"
package="domain"
default-lazy="false">

<class
name="domain.Property"
table="property"
>

<id
name="id"
type="java.lang.Integer"
column="property_id"
>
<generator class="increment" />
</id>

<many-to-one name="office" class="Office" column="office_id" cascade="none" />

<property
name="price"
type="java.lang.Integer"
column="price"
/>

</class>
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping
auto-import="true"
package="domain"
default-lazy="false">

<class
name="domain.Office"
table="office"
>

<id
name="id"
type="java.lang.Integer"
column="office_id"
>
<generator class="increment" />
</id>

<property
name="name"
type="java.lang.String"
column="name"
not-null="true"
length="30"
/>

</class>
</hibernate-mapping>