Lazy Loading with many-to-one

takashi · **Joined:** Tue Jul 06, 2010 7:56 am **Posts:** 4

I have 2 Beans with a many-to-one association connecting them: an Order and a Customer.
Both Beans are configured with lazy loading = false.
The Association is configured with lazy loading = proxy.

Code:

<hibernate-mapping>
  <class lazy="false" name="Order" table="Salesorder" optimistic-lock="version">
  ...
  <many-to-one name="customer"
       class="Customer"
       column="customer_id"
       not-null="true"
       lazy="proxy"/>
  ...

Code:

<hibernate-mapping>
  <class lazy="false" name="Customer" table="Customer" optimistic-lock="version">
  ...

In this scenario Hibernate ignores the lazy configuration for the association while loading an Order: the Customer record is fetched eagerly.
The lazy configuration for the Bean seems to override the lazy configuration for the association.
Is this assumption true? I didn't find a hint in the documentation.
Can I change this behaviour?

Greetings,
Takashi

takashi · **Joined:** Tue Jul 06, 2010 7:56 am **Posts:** 4

I have tested my lazy loading settings with an one-to-many association and in contrast to the many-to-one association the lazy attribute for the association is evaluated.
Here are my code snippets for two Beans, Order and Orderposition:

Code:

<hibernate-mapping>
  <class lazy="false" name="Order" table="Salesorder" optimistic-lock="version">
  ...
  <set name="positions" inverse="true" lazy="true" >
    <key column="salesorder_id" not-null="true"/>
    <one-to-many class="Orderposition"/>
  </set>
  ...

Code:

<hibernate-mapping>
  <class lazy="false" name="Orderposition" table="Orderposition" optimistic-lock="version">
  ...

With these settings the Orderpositions are really lazy loaded when loading the Order bean. Even though the Orderposition bean itself is configured with lazy = false.
Maybe this inconsistency to the many-to-one association is a Bug in Hibernate?
I have tested this behaviour with Hibernate 3.5.0 and 3.5.3.

rakesh436 · **Joined:** Tue Jul 06, 2010 11:37 am **Posts:** 6

Hi takashi,
didnt you get any error by giving lazy="proxy"??? for many to one.... i didnt try for associations up 2 now....please reply me for your way of doing.......

as per i know........the way of doing is......

there is no reason to brig in the entire collection when u only want to look at a few elements.you can help hibernate by specifying the proxy attribute in the <class> or <sub-class> element ,defining the class that should be used for lazy initialization.the class is the same as the class being mapped.

example :

<class name ="Group" proxy="Group">
<set lazy="true">
</set>
</class>

please reply after solving it.......

Thanks,
M.Rakesh

takashi · **Joined:** Tue Jul 06, 2010 7:56 am **Posts:** 4

Thx for your answer!

Quote:

didnt you get any error by giving lazy="proxy"???

Actually lazy="proxy" is the default value for this many-to-one attribute. Other possible values are "false" and "no-proxy".

As i have written in my second posting the lazy attribute for the <set> works fine for me.
1) <set name="..." lazy="true"> the collection is lazy loaded as expected.
2) <set name="..." lazy="false"> the collection is fetched eagerly.

The <many-to-one> makes my confusion.
1) <many-to-one name="..." lazy="proxy"/> the object is fetched eagerly. <<<<<Thats the problem
2) <many-to-one name="..." lazy="false"/> fetched eagerly too, as you expected.

VampBoy · **Posted:** Thu Jul 08, 2010 11:52 am

To lazy load a many to one the class on the one side also has to be marked as lazy as it needs to be able to be proxied.

takashi · **Joined:** Tue Jul 06, 2010 7:56 am **Posts:** 4

Thx for your answer!

I suppose the collection object used for the ony-to-many association is proxied in contrast to the object on the one side in the many-to-one association. This is the major difference to many-to-one. It seems to be inconsistent for me. Where would I improve the documentation to give other users a hint for this behaviour? I think it's an important aspect of associations.