many-to-many with additional attributes

Pimmi · **Posted:** Mon Aug 16, 2004 4:13 am

Hibernate version: 2.1

Name and version of the database you are using: Firebird 1.5

hi,

i did some exercises with hibernate and i am content with the most functions of hibernate. today i want to tried an many-to-many association with additional attributes, as i had problems i tried to find answers in the documentation and here. but i still have a problem:

I have two classes: Employee (that is a subclass of person) and Publication. Between this 2 classes there is an association class Emp_Pub. I modelled this association class as it is told in the documentation, but now i have problems in creating objects - i think there is a fault in my java-class Emp_Pub

Person.hbm.xml

Code:

<class name="Person"
      table="PERSON"
      lazy="true">

   <id name="pId"
     type="long"
     column="PID">
     <generator class="native"/>
   </id>

...

   <joined-subclass name="Employee"
      table="EMPLOYEE"
      lazy="true">

      <key column="PID"/>

      <property name="education"
              type="string"
              column="EDUCATION"
              length="20"
              not-null="true"
              update="true"/>

         <many-to-one name="department"
             class="Department"
             cascade="all"
             not-null="true"
             column="DEPART_ID"
             update="true"/>

      
           <set name="publications" table="EMP_PUB">
            <key foreign-key="FK_EMPLOYEE_PID" column="EMPLOYEE_PID"/>

            <composite-element class="Employee_Pub">
              <property name="created" type="date"/>
             <many-to-one name="publication" foreign-key="FK_PUBLICATION_ID" column="PUBLICATION_PUBID" not-null="true"/>
            </composite-element>

   </joined-subclass>

   ...

</class>

Publication.hbm.xml

Code:

   <class name="Publication" table="PUBLICATION">
          <id name="pubId" column="PUBID" type="long">
                  <generator class="increment"/>
          </id>
          <property name="title" column="TITLE" type="string"/>
             <property name="publicated" column="PUBLICATED" type="boolean"/>
             <set name="employees"
             inverse="true"
             lazy="true"
             table="EMP_PUB"
                 cascade="all">
                 <key>
                     <column name="PUBLICATION_PUBID" not-null="true"/>
                 </key>
                 <many-to-many class="Employee">
                     <column name="EMPLOYEE_PID" not-null="true"/>
                 </many-to-many>
             </set>
        </class>

Employee_Pub.java

Code:

public class Employee_Pub {

    private Date created;
    private Employee employee;
    private Publication publication;

... getter & setter

now to my problem: how must the Employee_Pub.hbm.xml file musst looke like, i made some tries, but nothing worked.

thanks for helping, sorry that my english is not the best

Pimmi · **Posted:** Mon Aug 16, 2004 10:29 am

hm...

does anybody know a complete example of a many-to-many association with an additional attribute? i think this would be helpful for me, because i could only find fragments of of code. i would be very pleased!!

Pimmi · **Posted:** Tue Aug 17, 2004 8:33 am

i am really disappointed, that no one can or want to help me, i really do not know how to modell the xml-file of the association-class - i am also not sure how the java-file of this class has to be modelled - the two referencing objects (or only the primary keys of them?) and the additional attribut? or am i completly wrong?

as i told before: i miss a extensive example of a many to many relation with some additional properties. i can hardly not believe, that no other person had this problem before.

anthony · **Posted:** Tue Aug 17, 2004 8:56 am

understand "utilisateur" as "user"

utilisateur.hbm.xml

Code:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>   
<class name="XXX.Utilisateur" table="UTILISATEUR">      
<id column="LOGIN" name="login">      
<generator class="assigned"/>      
</id>      
<property column="NOM" name="nom" not-null="true" />      ...      
<bag name="roles" table="UTILISATEUR_ROLE">            
<key column="ID_UTILISATEUR"/>               
<composite-element class="XXX.UtilisateurRole">        
<property name="mail" />                                      
<many-to-one column="ID_ROLE" name="role" class="XXX.Role"/>    </composite-element>            
</bag>   
</class></hibernate-mapping>

role.hmb.xml

Code:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>   
<class name="com.auchan.balisage.bo.habilitation.Role" table="ROLE">
<id column="ID_ROLE" name="idRole">      
<generator class="sequence">         
<param name="sequence">SEQ_ROLE</param>   
</generator>
</id>
<property column="NOM" name="nom" not-null="false" />
                          ...   
</class>
</hibernate-mapping>

UtilisateurRole.hbm.xml

Code:

Fichier Role.hbm.xml :<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd"><hibernate-mapping>   
<class name= "XXX.UtilisateurRole" table="UTILISATEUR_ROLE">   <composite-id>
<key-many-to-one name="utilisateur" class="XXX.Utilisateur" column="ID_UTILISATEUR"/>     
<key-many-to-one name="role" classXXX.Role"column="ID_ROLE"/>    </composite-id>
<property name="mail" column="MAIL" />   
</class>
</hibernate-mapping>

Pimmi · **Posted:** Tue Aug 17, 2004 12:34 pm

Merci beaucoup anthony! now everything is clear and my testapplication works well!

anthony · **Posted:** Tue Aug 17, 2004 4:27 pm

you're welcome!
next time just be more patient ;)

sebi2706 · **Joined:** Wed Jul 07, 2004 4:38 am **Posts:** 5

Hi, I got nearly the same problem, I understand your sample Anthony, but I'm getting a little bit lost when I tried to implement th userRole java file , specially I had some CGLIB probs and I'm not sure i overided equals() et hashcode() in the right manner. Could it be possible that you post your code of the java file?
Merci d'avance !
Sebi

dangmp · **Joined:** Tue Aug 24, 2004 4:25 am **Posts:** 14

I am facing the same problem as well. I would like to know how 3 classes look like. Thanks alot.

cmou · **Joined:** Mon Mar 01, 2004 3:41 pm **Posts:** 9

Hi anthony,

i was looking for a solution to this problem as well, and i tried your code. The classes compile fine. What happens to me when i do a schema export using the schemaexport Ant task, it fails. The message is:

Quote:

Schema text failed: net.sf.hibernate.PropertyNotFoundException: Could not find a setter for property utilisateur in class XXX.UtilisateurRole

Do you know how to work around it?

Also, when looking at the classes, the Role class doesn't have a collection of Utilizateur. In the project i'm working on, i also need such a collection for the bidirectional relationship. i tried the <bag> mapping on the Role end and it doesn't work.

Would you please tell me whether there's a way to work this out?

Many thanks! i really appreciate your help!

celia

anthony wrote:

understand "utilisateur" as "user"

utilisateur.hbm.xml

Code:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>   
<class name="XXX.Utilisateur" table="UTILISATEUR">      
<id column="LOGIN" name="login">      
<generator class="assigned"/>      
</id>      
<property column="NOM" name="nom" not-null="true" />      ...      
<bag name="roles" table="UTILISATEUR_ROLE">            
<key column="ID_UTILISATEUR"/>               
<composite-element class="XXX.UtilisateurRole">        
<property name="mail" />                                      
<many-to-one column="ID_ROLE" name="role" class="XXX.Role"/>    </composite-element>            
</bag>   
</class></hibernate-mapping>

role.hmb.xml

Code:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>   
<class name="com.auchan.balisage.bo.habilitation.Role" table="ROLE">
<id column="ID_ROLE" name="idRole">      
<generator class="sequence">         
<param name="sequence">SEQ_ROLE</param>   
</generator>
</id>
<property column="NOM" name="nom" not-null="false" />
                          ...   
</class>
</hibernate-mapping>

UtilisateurRole.hbm.xml

Code:

Fichier Role.hbm.xml :<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd"><hibernate-mapping>   
<class name= "XXX.UtilisateurRole" table="UTILISATEUR_ROLE">   <composite-id>
<key-many-to-one name="utilisateur" class="XXX.Utilisateur" column="ID_UTILISATEUR"/>     
<key-many-to-one name="role" classXXX.Role"column="ID_ROLE"/>    </composite-id>
<property name="mail" column="MAIL" />   
</class>
</hibernate-mapping>

cmou · **Joined:** Mon Mar 01, 2004 3:41 pm **Posts:** 9

Hi,

The problem with schema generation and bidiretional many-to-many issue was solved. Here's my code example:

Suppose a member can belong to many organizations, and one organization can have many members; the linking table has other properties defining the role of a particular member in a particular organization:

* In the mapping for the "member" table, i have this:
-------
<bag name="orgs" lazy="true" outer-join="true" table="member_org">
<key column = "member_no" />
<many-to-many class="com.blah.member.data.Organization" column="org_no" />
</bag>
-------

* Then in the mapping for the "organization" table, i have this:
---------
<bag name="members" lazy="true" inverse="true" outer-join="true" table="member_org">
<key column = "org_no" />
<many-to-many class="com.blah.member.data.Member" column="member_no" />
</bag>
---------

* Then in the mapping for the linking table with other properties, i have this:
---------
<composite-id>
<key-many-to-one name="member" class="com.blah.member.data.Member" column="member_no"/>
<key-many-to-one name="org" class="com.blah.member.data.Organization" column="org_no"/>
</composite-id>

---------

This generates everything nicely.

Thanks to everyone who contributed to my thinking!