Hi All,

I am coming across an issue in my sample application. Please help.

I have 4 objects in my sample application: Customer, Order, OrderItem, Product and their associations are as follows:
Customer --> Order (One-to-Many Bi-directional)
Order --> OrderItem (One-to-Many Uni-directional)
OrderItem --> Product (Many-to-One Uni-directional)

And the 4 tables are CUSTOMER, C_ORDER, ORDER_ITEM, PRODUCT.

Through my application I created an order with 2 order items. This created 1 record in C_ORDER table and 2 records in ORDER_ITEM table. Please note that this is the only Order record in the DB. Then I tried to fetch details of all orders in my application along with its order items with eager loading using the following statement:

List<Order> orderList = session.createQuery(“from Order o left join fetch o.orderItems”).list();

The above statement has returned 2 Order records in the list. Both these records contain the same data. And there is only one Order in the DB. I captured the SQL generated by Hibernate and it is as below:
select order0_.ORDER_ID as ORDER1_1_0_, orderitems1_.ORDER_ITEM_ID as ORDER1_2_1_, order0_.ORDER_TOTAL as ORDER2_1_0_, order0_.CUSTOMER_ID as CUSTOMER3_1_0_, orderitems1_.ORDER_ITEM_QUANTITY as ORDER2_2_1_, orderitems1_.PRODUCT_ID as PRODUCT3_2_1_, orderitems1_.ORDER_ID as ORDER4_0__, orderitems1_.ORDER_ITEM_ID as ORDER1_0__ from C_ORDER order0_ left outer join ORDER_ITEM orderitems1_ on order0_.ORDER_ID=orderitems1_.ORDER_ID

When I ran the above query in the HSQL DB manager, it returned two records as below:
ORDER1_1_0_ ORDER1_2_1_ ORDER2_1_0_ CUSTOMER3_1_0_ ORDER2_2_1_ PRODUCT3_2_1_ ORDER4_0__ ORDER1_0__
----------- ----------- ----------- -------------- ----------- ------------- ---------- ----------
1 1 0.0 1 2 2 1 1
1 2 0.0 1 1 1 1 2
2 row(s) in 1 ms
which seemed correct. I expected that the above 2 records should have been mapped by Hibernate into one Order object containing two OrderItem objects. But surprisingly two Order objects were returned by my HQL query. I wonder why this is happening.

I am attaching the hbm.xml files below for reference:

Customer.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
<class name="com.bpp.cm.Customer" table="CUSTOMER">
<id name="id" type="long" column="CUSTOMER_ID">
<generator class="native"/>
</id>
<property name="name" type="string" column="CUSTOMER_NAME"/>
<property name="phone" type="string" column="CUSTOMER_PHONE"/>

<set name="orders" inverse="true">
<key column="CUSTOMER_ID"/>
<one-to-many class="com.bpp.cm.Order"/>
</set>
</class>
</hibernate-mapping>


Order.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
<class name="com.bpp.cm.Order" table="C_ORDER">
<id name="id" type="long" column="ORDER_ID">
<generator class="native"/>
</id>
<property name="total" type="float" column="ORDER_TOTAL"/>
<many-to-one name="customer" column="CUSTOMER_ID" class="com.bpp.cm.Customer" not-null="true"/>
<set name="orderItems" cascade="all">
<key column="ORDER_ID"/>
<one-to-many class="com.bpp.cm.OrderItem"/>
</set>
</class>
</hibernate-mapping>


OrderItem.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
<class name="com.bpp.cm.OrderItem" table="ORDER_ITEM">
<id name="id" type="long" column="ORDER_ITEM_ID">
<generator class="native"/>
</id>
<property name="quantity" type="integer" column="ORDER_ITEM_QUANTITY"/>
<many-to-one name="product" column="PRODUCT_ID" class="com.bpp.cm.Product" lazy="false"/>
</class>
</hibernate-mapping>


Product.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
<class name="com.bpp.cm.Product" table="PRODUCT">
<id name="id" type="long" column="PRODUCT_ID">
<generator class="native"/>
</id>
<property name="name" type="string" column="PRODUCT_NAME"/>
<property name="price" type="float" column="PRODUCT_PRICE"/>
</class>
</hibernate-mapping>

I guess you are using eager fetchtype ?

Then you'll resolve it by either removing eager and get the set when you need it, or use the "DistinctResultTransformer.INSTANCE.transformList"

EDIT:

OK - note to self, learn to read the complete post prior to posting. You are not using eager, so forget what I wrote above

Perlovmo,

Thanks for your response. My scenario is that in general I want to lazy load OrderItems in an Order. But in a particular function I would like to eagerly load the OrderItems. So, I used join as part of my query in this particular function. This is baed on example given on page 587 in JAVA PERSISTENCE WITH HIBERNATE book.

I am thinking I will try out the same thing on a simpler example with just 2 entities and see. Meanwhile, if you find something please let me know.

Thanks.

bjagan this is a FAQ. See here:
http://web.archive.org/web/200702021455 ... 7.html#A12

To the webmaster: why does the current site not have a FAQ page???

xerces,

Thanks a lot! This FAQ exactly answers my question. But I somehow feel this behavior from Hibernate, for that matter from any ORM is not correct. When mapping/converting the data from SQL Resultset into objects, I guess this could have been taken care.

Thanks again!