I have a user object with a many-to-many relationship table user_relationship. When I call user.getRelations(), it's null in the set. Any idea why? Is there something wrong in the "relations" mapping?

Thanks.



Here is the table DDL:

CREATE TABLE user_relationship
(
`id` VARCHAR(48) NOT NULL,
`user_id` VARCHAR(48) NOT NULL,
`friend_id` VARCHAR(48) NOT NULL,
`relationship_flag_id` VARCHAR(2) NOT NULL DEFAULT 'F',
PRIMARY KEY(`id`),
INDEX `User_Relationship_Composite_PK`(`user_id`, `friend_id`),
CONSTRAINT `FK_user_relationship_user` FOREIGN KEY `FK_user_relationship_user` (`user_id`)
REFERENCES `user` (`id`),
CONSTRAINT `FK_user_relationship_friend` FOREIGN KEY `FK_user_relationship_friend` (`friend_id`)
REFERENCES `user` (`id`),
CONSTRAINT `FK_user_relationship` FOREIGN KEY `FK_user_relationship` (`relationship_flag_id`)
REFERENCES `relationship` (`id`)
)




UserRelationship mapping:

<?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="UserRelationship"
table="user_relationship"
lazy="true"
>
<cache usage="read-write" />

<id
name="id"
column="id"
type="java.lang.String"
unsaved-value="null"
>
<generator class="uuid.hex">
<!--
To add non XDoclet generator parameters, create a file named
hibernate-generator-params-UserRelationshipData.xml
containing the additional parameters and place it in your merge dir.
-->
</generator>
</id>

<many-to-one
name="friend"
class="User"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="friend_id"
not-null="true"
/>

<many-to-one
name="owner"
class="User"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="user_id"
not-null="true"
/>

<many-to-one
name="relationship"
class="Relationship"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="relationship_flag_id"
not-null="true"
/>

<!--
To add non XDoclet property mappings, create a file named
hibernate-properties-UserRelationshipData.xml
containing the additional properties and place it in your merge dir.
-->

</class>

</hibernate-mapping>




UserRelationship class snippet:

public class UserRelationship implements Serializable
{
private String id;
private User owner;
private User friend;
private Relationship relationship;
}



User class mapping snippet:

<hibernate-mapping
>
<class
name="User"
table="user"
lazy="false"
>
<cache usage="read-write" />

<set name="relations" lazy="true" table="user_relationship">
<key column="user_id"/>
<composite-element class="UserRelationship">
<parent name="owner"/>
<many-to-one name="friend" class="User" column="friend_id" not-null="true"/>
<many-to-one name="relationship" class="Relationship" column="relationship_flag_id" not-null="true"/>
</composite-element>
</set>
</hibernate-mapping>

Bump. Anyone can help me out?

Hi,

You should use a lazy=false.

A brief explanation would be: If you use a lazy=true, then you must have a opened session.

Don't forget to rate,

Regards.

It's not about the lazy fetch. I have the session open.

It seems that the association is completely ignored.

I've seen similar behavior if your association mapping definition isn't defined in your hibernate.cfg.xml file.

Its a open session problem. its called Open Session view pattern. Its works in Transaction scoped level. Hence its better for u to use HQL query to get the parent object, then u'ld definetly get the collections rather than null.