Hibernate - Spring - problem with mapping (many-to-many)

Question

Hello,
I want to map the following situation. I have a table called EDUCATION and a table called SCHOOLS. Between those tables I have an associative table called EDUCATION_SCHOOLS. The (usefull) fields:
EDUCATION:
id (long) - PK
name (varchar)
versionNr (long)
SCHOOLS:
id (long) - PK
name (varchar)
versionNr (long)
EDUCATION_SCHOOLS:
id (long) - PK
education_id (long) (FK to EDUCATION.id)
school_id (long) (FK to SCHOOLS.id)
name (varchar)
versionNr (long)
Their is a Unique Constraint between EDUCATION_SCHOOLS.education_id and EDUCATION_SCHOOLS.school_id.
What I want to be able to do:
EDUCATION: select, update, insert
SCHOOLS: select, update, insert
EDUCATION_SCHOOLS: select, update (only the non-FK fields), insert
I never want to delete anything in those tables. (and it's never ever going to be an option either)
Hibernate version:
Hibernate-Version: 3.0.5
Mapping documents:
Education:
<hibernate-mapping>
     <class name="##.Education" table="EDUCATION">
          <id name="id" column="ID" type="java.lang.Long">
               <generator class="sequence">
                    <param name="sequence">EDUCATION_SEQ</param>
               </generator>
          </id>
          <version name="versionNr" column="VERSIONNR" type="long"/>
          <property name="name" column="NAME" type="string" />
        <set name="SCHOOLS" table="EDUCATION_SCHOOLS">
            <key column="EDUCATION_ID" />
            <many-to-many class="##.Schools" column="SCHOOL_ID" lazy="false" />
        </set>
</hibernate-mapping>
Schools:
<hibernate-mapping>
     <class name="##.Schools" table="SCHOOLS">
          <id name="id" column="ID" type="java.lang.Long">
               <generator class="sequence">
                    <param name="sequence">SCHOOLS_SEQ</param>
               </generator>
          </id>
          <version name="versionNr" column="VERSIONNR" type="long"/>
          <property name="name" column="NAAM_NAME" type="string" />
        <set name="educations" table="EDUCATION_SCHOOLS" inverse="true" cascade="none">
            <key column="SCHOOL_ID" />
            <many-to-many class="##.Schools" column="SCHOOL_ID" lazy="proxy"/>
        </set>
</hibernate-mapping>
Education_schools:
<hibernate-mapping>
<class name="##.EducationSchools" table="EDUCATION_SCHOOLS">
           <id name="id" column="ID" type="java.lang.Long" unsaved-value="0">
               <generator class="sequence">
                    <param name="sequence">SEQ_EDUCATION_SCHOOLS</param>
               </generator>
          </id>
          <version name="versionNr" column="VERSIONNR" type="long" />
          <many-to-one name="education" class="##.Education" cascade="none" lazy="proxy"
                       column="EDUCATION_ID" not-null="true"/>
        <many-to-one name="schools" class="##.Schools" cascade="none" lazy="proxy"
                    column="SCHOOL_ID" not-null="true"/>  
</hibernate-mapping>   
Name and version of the database you are using:
Oracle XE 10g
I am able to:
EDUCATION: select, insert, update
SCHOOLS: select, insert, update
EDUCATION_SCHOOLS: select
Problems:
EDUCATION_SCHOOLS: when I try to insert, I sometimes get unique constraint violations. (when I should get them, thus I'm trying to insert something that already exists .. but how do I stop Hibernate from Inserting?)
EDUCATION_SCHOOLS: when I try to update, sometimes it works, but often I get:
23:03:55,484 [http-8081-1] ERROR be.vlaanderen.lne.vea.epb.ui.struts.EpbExceptionHandler - org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [##.EducationSchools] with identifier [null]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [##.EducationSchools#<null>]
ex.getMessage() Object of class [##.EducationSchools] with identifier [null]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [##.EducationSchools#<null>]
org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [##.EducationSchools] with identifier [null]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [##.EducationSchools#<null>]
Caused by: org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect):As you can see from the stacktrace I use Spring for the transactionManager: org.springframework.orm.hibernate3.HibernateTransactionManager in which I use e sessionFactory: org.springframework.orm.hibernate3.LocalSessionFactoryBean
In my DAO, I try to save with the regular this.getHibernateTemplate().saveOrUpdate that has always worked for me.
Another problem I have:
when i update "name" in EDUCATION, the records with that ID are delete from EDUCATION_SCHOOLS ...
As I am experiencing 3 different problems, I'm pretty sure something is wrong in the mapping files .. however I fail to find out what .. Any input would be greatly appreciated.
(I translated some class/table-names, that's what the ## cause)
Edited by: Bart_Blommaerts on Jul 29, 2008 11:53 PM

Answer 1

Thank you for your input.
When I try what you suggest, I still get the same error:
16:39:30,406 [http-8081-1] ERROR ###.EpbExceptionHandler - org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [###.EducationSchools] with identifier [2]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [###.EducationSchools#2]
ex.getMessage() Object of class [###.EducationSchools] with identifier [2]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [###.EducationSchools#2]
org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [###.EducationSchools] with identifier [2]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [###.EducationSchools#2]
Caused by: org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [###.EducationSchools#2]If you had to map the database tables, I'm trying to map, how would you do it?