Hi

I'm using one to many mapping with *Set*,,,, while inserting data its giving the Error like "Foreign key constraint failed"

My Mapping files are :

[*]1
<?xml version="1.0"?>
<!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.sample.User" table="x_user">
<id name="userid" type="long" column="user_id">
<generator class="increment"/>
</id>
<property name="userName" type="string" column="user_name"/>

<set name="roles" lazy="false" cascade="all">
<key column="user_id"/>
<one-to-many class="com.sample.Role"/>
</set>
</class>
</hibernate-mapping>

[*]2


<?xml version="1.0"?>
<!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.sample.Role" table="x_role">
<id name="roleid" type="long" column="role_id">
<generator class="increment"/>
</id>
<property name="roleName" type="string" column="role_name"/>
</class>
</hibernate-mapping>

[*]Tables structure :



CREATE TABLE x_user (user_id INT NOT NULL AUTO_INCREMENT,
user_name VARCHAR(30) NOT NULL,
PRIMARY KEY(user_id ))ENGINE =InnoDB;


CREATE TABLE x_role (role_id INT NOT NULL AUTO_INCREMENT ,
user_id INT NOT NULL ,
role_name VARCHAR(30) NOT NULL,
PRIMARY KEY(role_id ),
CONSTRAINT `0-122` FOREIGN KEY( user_id) REFERENCES x_user (user_id) )ENGINE =InnoDB;


Please correct me where i have done the wrong and how to rectify that ?

I hopes can get quick reply.

Thanks,
Malli.

This is covered in the Parent/Child example in the Hibernate documentation: http://docs.jboss.org/hibernate/stable/ ... child.html

Basically, it happens because you have declared x_role.user_id column NOT NULL, but you have not mapped the corresponding column in your Role class.

Hi,

you use a unidirectional one-to-many association on a foreign key,
which is an unusual case, and is not recommended
(see http://docs.jboss.org/hibernate/core/3.3/reference/en/html/associations.html#assoc-unidirectional-12m section 7.2.3 ).

Your current mapping maps the foreign key on the schema with NOT NULL
Therefore before you persists a new role instance, it already must be assigned to a user.

Solution: try to user the not-null="true" property



Or better: switch to another type of mapping which use is not discouraged.

Hi,
Thanks lot its useful for me.

Thanks
Malli.