lazy loading issue

amit_deshpande · **Joined:** Wed Nov 01, 2006 5:55 am **Posts:** 3

Hibernate version:3.0
JBoss version :4.0.3
I have two classes User and CustomerInfo and their corresponding hbm.xmls
and their is one to one mapping in between these two relations as

user.hbm.xml
<hibernate-mapping>
..
..

<one-to-one
name="CustomerInfo"
property-ref="user"
cascade="all"
lazy="no-proxy"
/>

</hibernate-mapping>

and the file
customerinfo.hbm.xml
<hibernate-mapping>
..
..


<many-to-one
name="user"
column="user_id"
unique="true"
not-null="true"
/>
</hibernate-mapping>

When i fire query on table user the select query for customerinfo is also gets fired(no lazy loading).So can any one help me so that the select query for customerInfo should not get fired

In short how to achieve lazy laoding in case of one to one mapping
<one-to-one
lazy="false|no-proxy|proxy"
/>
nothing works ! Why hibernate people removed lazy=true in case of one-to-one mapping !

Thnx and regards
Amit Deshpande

jbuswell · **Joined:** Fri Oct 27, 2006 6:53 pm **Posts:** 3

In addition to making lazy = proxy, you need to specify the fetch mode for this association. You can either use fetch="join" on the <one-to-one> mapping or you can set the fetch mode in your queries that return users (e.g., criteria.setFetchMode("customerInfo", FetchMode.JOIN) ).

amit_deshpande · **Joined:** Wed Nov 01, 2006 5:55 am **Posts:** 3

thnx for your reply

fetch = "join|select"
when one specifies fetch = "join" Hibernate retrieves the associated instance or collection in the same SELECT, using an OUTER JOIN.

And one more thing to add
when i really tried it in my application it seems that it is not working means the select query for other table(customer info ) get's fired also.

Preetam · **Joined:** Tue Apr 18, 2006 11:05 am **Posts:** 5

hi amit,
i guess you probaly want to have lazy loading for one-to-one mapping in case of hibernate. typically you have one-to-one-or-zero kind of mapping right ?
i have the same issue with me.
can any one help us in mapping one-to-one ( more precisely one-to-one-or-zero ) in hibernate?

Thanks
~pp

damnhandy · **Posted:** Sun Nov 05, 2006 1:04 pm

Amit,

here's what you mappings should look like:

Code:

 <!-- bi-directional one-to-one association to CustomerInfo -->
<one-to-one
  name="CustomerInfo"
  property-ref="user"
  cascade="all"
  lazy="proxy"
  constrained="true"
/>

<!-- bi-directional one-to-one association to User -->

<many-to-one
   name="user"
   column="user_id"
   unique="true"
   not-null="true"
   lazy="proxy"
/>
</hibernate-mapping> 

Note that on CustomerInfo, we have declared lazy="proxy" (which is equivilent to the old lazy="true") and constrained="true". The attribute lay="no-proxy" only works if you use bytecode instrumentation. If you don't know what I mean, then you're probably not using it. The constrained attribute is also important as if it is set to false, proxying is impossible, and this the association is always eagerly loaded.

Although jbuswell suggested using fetch="join", this will not solve your problem. When you use fect="join", you effectively disable lazy-loading as the entities are loading 2 objects in one SQL call. You should use the default fetch mode of select.

Ryan-

Preetam · **Joined:** Tue Apr 18, 2006 11:05 am **Posts:** 5

Quote:

<one-to-one
name="CustomerInfo"
property-ref="user"
cascade="all"
lazy="proxy"
constrained="true"
/>



<many-to-one
name="user"
column="user_id"
unique="true"
not-null="true"
lazy="proxy"
/>
</hibernate-mapping>

hi damnhandy ,
the mappping you suggested above did not work.
BTW
from http://www.hibernate.org/162.html ... i have used this mapping

<many-to-one name="CustomerInfo"
class="CustomerInfo"
column="user_id"
unique="true"
insert="false"
update="false"
cascade="all"/>

and
<one-to-one
name="user"
class="User"
constrained="true"/>

which worked !

igorochok · **Joined:** Wed Nov 08, 2006 11:14 am **Posts:** 2

hi everyone!

I have similar problem with lazy loading. I have two tables with mapping like this:

Code:

<class name="User" table="User">
        <id name="id" column="id">
            <generator class="sequence">
                <param name="sequence">tp_seq</param>
            </generator>
        </id>

        <properties name="uniqueProps">
            <property name="firstName" column="firstName" type="string"/>
            <property name="lastName" column="lastName" type="string"/>
            <property name="middleName" column="middleName" type="string"/>
        </properties>
...
</class>

<class name="Customer" table="Customer">
        <id name="id" column="id">
            <generator class="sequence">
                <param name="sequence">tp_seq</param>
            </generator>
        </id>

            <property name="firstName" column="firstName" type="string"/>
            <property name="lastName" column="lastName" type="string"/>
            <property name="middleName" column="middleName" 

<many-to-one name="user" class="User" property-ref="uniqueProps">
            <column name="firstName"/>
            <column name="lastName"/>
            <formula>Igor</formula>
</many-to-one>
...
</class>

So, I want select customer with lazy loading of appropriate user and select user with lazy loading of appropriate customer. It's doesn't work in this case. I think the problem is that the relation between these classes not uses primary key, and I have to use "property-ref" attribute.
Does anyone can help me?!

amit_deshpande · **Joined:** Wed Nov 01, 2006 5:55 am **Posts:** 3

This is a different issue.U want lazy loading if i am not wrong.

I think this will not work because you have to specify that primary key of User in Customer's hbm.xml file
Try to keep that id of User table in Customer table so that u will get records from user table when you are fetching records for Customer.

thnx and regards
Amit Deshpande

igorochok · **Joined:** Wed Nov 08, 2006 11:14 am **Posts:** 2

First af all, thanks a lot for reply.
My DB has been already designed before me, so I can't change it. The tables I use in this case relate to each other through fields that are not a primary key and a foreign key, they are just unique.
The question is, if I'm not use primary key in a relation, can I have lazy loading?