Hi, folks

I am learning Hibernate and I am following the book 'hibernate quickly'. When I run the the example from the website site(http://www.manning.com/peak/, following the source code link) for chapter 5, after running the ant to create the tables, I found that in the 'join' or 'link' tables between the 2 tables, m_events & m_attendees, and the 'link' table, event_attendees, which should have only 2 PKs from the 2 tables, has an unexpected column, named 'elt'?

The mapping files are the follows:

//======= EventManyToMany.hbm.xml =======//

<?xml version="1.0"?>
<!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.manning.hq.ch05.manytomany.EventManyToMany" table="m_events">
<id name="id" column="uid" type="long" unsaved-value="null">
<generator class="native"/>
</id>
<property name="name" type="string" length="100"/>
<property name="startDate" column="start_date"
type="date"/>
<property name="duration" type="integer"/>
<many-to-one name="location" column="location_id"
class="com.manning.hq.ch05.manytomany.LocationManyToMany"/>
<set name="speakers" table="event_speakers" cascade="all">
<key column="event_id"/>
<many-to-many class="com.manning.hq.ch05.manytomany.SpeakerManyToMany"/>
</set>
<set name="attendees" table="event_attendees" cascade="all">
<key column="event_id"/>
<many-to-many class="com.manning.hq.ch05.manytomany.AttendeeManyToMany"/>
</set>
</class>
</hibernate-mapping>

//=== AttendeeManyToMany.hbm.xml =====//

<?xml version="1.0"?>
<!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.manning.hq.ch05.manytomany.AttendeeManyToMany" table="m_attendees">
<id name="id" column="uid" type="long">
<generator class="native"/>
</id>
<property name="firstName" type="string" length="20"/>
<property name="lastName" type="string" length="20"/>
<set name="events" table="event_attendees" cascade="all">
<key column="attendee_id"/>
<many-to-many class="com.manning.hq.ch05.manytomany.EventManyToMany"/>
</set>
</class>
</hibernate-mapping>

The resultant 'event_attendees' table will have structure like this:

event_id elt attendee_id

The 'elt' field is the one that is confusing me.

Could anyone give me some hints why hibernate created such field?

Btw, I have hibernate 3.0.

Thanks in advance!

X.Chen

Just got it. That change I made is like this :

//======= EventManyToMany.hbm.xml =======//
...

set name="attendees" table="event_attendees" cascade="all">
<key column="event_id"/>
<many-to-many column="attendee_id" class="com.manning.hq.ch05.manytomany.AttendeeManyToMany"/>
</set>


//=== AttendeeManyToMany.hbm.xml =====//
...

<set name="events" table="event_attendees" cascade="all">
<key column="attendee_id"/>
<many-to-many column="event_id" class="com.manning.hq.ch05.manytomany.EventManyToMany"/>
</set>

Notice the symetry by adding the 'column' attribute in both file.

FYI, the "elt" symbol that has been mentioned in several posts is the default column name hibernate uses. It generally indicates that you failed to provide some mapping information for a key column, so Hibernate makes one up.