23.3. Customer/Order/Product
In this section we consider a model of the relationships between
Customer
, Order
, Line Item
and Product
. There is a one-to-many association between Customer
and Order
, but how can you represent Order
/ LineItem
/ Product
? In the example, LineItem
is mapped as an association class representing the many-to-many association between Order
and Product
. In Hibernate this is called a composite element.

The mapping document will look like this:
<hibernate-mapping> <class name="Customer" table="customers"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <set name="orders" inverse="true"> <key column="customer_id"/> <one-to-many class="Order"/> </set> </class> <class name="Order" table="orders"> <id name="id"> <generator class="native"/> </id> <property name="date"/> <many-to-one name="customer" column="customer_id"/> <list name="lineItems" table="line_items"> <key column="order_id"/> <list-index column="line_number"/> <composite-element class="LineItem"> <property name="quantity"/> <many-to-one name="product" column="product_id"/> </composite-element> </list> </class> <class name="Product" table="products"> <id name="id"> <generator class="native"/> </id> <property name="serialNumber"/> </class> </hibernate-mapping>
customers
, orders
, line_items
and products
hold customer, order, order line item and product data respectively. line_items
also acts as an association table linking orders with products.
create table customers ( id BIGINT not null generated by default as identity, name VARCHAR(255), primary key (id) ) create table orders ( id BIGINT not null generated by default as identity, customer_id BIGINT, date TIMESTAMP, primary key (id) ) create table line_items ( line_number INTEGER not null, order_id BIGINT not null, product_id BIGINT, quantity INTEGER, primary key (order_id, line_number) ) create table products ( id BIGINT not null generated by default as identity, serialNumber VARCHAR(255), primary key (id) ) alter table orders add constraint ordersFK0 foreign key (customer_id) references customers alter table line_items add constraint line_itemsFK0 foreign key (product_id) references products alter table line_items add constraint line_itemsFK1 foreign key (order_id) references orders