How come foreign key of the email table(PersonID) will be set to the primary key of person table since i set the inverse="false"? Base on the documentation, the inverse has to be set to true inorder to do this.

Hibernate version:3

Mapping documents:


CREATE TABLE person
(
personid int4,
person_name varchar(20)
)

<?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="source.Person" table="Person">

<id name="personID" column="PersonID" type="int" >
<generator class="increment"/>
</id>

<property name="personName" column="Person_Name" type="java.lang.String" not-null="false"/>

<set name="emails" table="Email" inverse="false" cascade="all-delete-orphan" lazy="true" >
<key column="PersonID"/>
<one-to-many class="source.Email"/>
</set>

</class>

</hibernate-mapping>


CREATE TABLE email
(
emailid int4,
personid int4,
email varchar(20) null
)
<?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="source.Email" table="Email" >

<id name="emailID" column="EmailID" type="int" unsaved-value="0" >
<generator class="increment"/>
</id>

<property name="email" column="Email" type="java.lang.String" not-null="false" />
<many-to-one name="person" class="source.Person" cascade ="save-update" column="PersonID"/>
</class>

</hibernate-mapping>



Code between sessionFactory.openSession() and session.close():

Person person = new Person();
Email email = new Email();

email.setEmail("[email protected]");
email.setPerson(person);
person.getEmails().add(email);

session.save(person);



Name and version of the database you are using:
postgres 8


The generated SQL (show_sql=true):


Hibernate: insert into Person (PersonID) values (?)
Hibernate: insert into Email (PersonID, Email, EmailID) values (?, ?, ?)
Hibernate: update Email set PersonID=? where EmailID=?

You ask "How come foreign key of the email table(PersonID) will be set to the primary key of person table since i set the inverse="false"?

The reason that the foreign key of the email table (PersonId) will be set to the primary key of the person table i the following part of you mapping document:

<many-to-one name="person" class="source.Person" cascade ="save-update" column="PersonID"/>

The reference will allways be established in the database no matter what value the inverse has.

Setting inverse="false" only says that the association between a person and his email shouldn't be bidirectional. Set inverse = "false" means that you can't say person.getEmails();

Ii still can use person.getEmails. How?

Query q = session.createQuery("from Person d where d.personID=1");
List list = q.list();
Iterator iter = list.iterator();
Email email = new Email();

while(iter.hasNext()){

Person person = (Person)iter.next();
System.out.println("name="+person.getPersonName());
email = (Email) person.getEmails().iterator().next();
System.out.println("email="+email.getEmail());
}

output in console:
Hibernate: select person0_.PersonID as PersonID, person0_.Person_Name as Person2_2_ from Person person0_ where person0_.PersonID=1
name=andy lau
Hibernate: select emails0_.PersonID as PersonID__, emails0_.EmailID as EmailID__, emails0_.EmailID as EmailID0_, emails0_.Email as Email3_0_, emails0_.PersonID as PersonID3_0_ from Email emails0_ where emails0_.PersonID=?
[email protected]

Hi why,

If you want to be able to say person.getEmails() you have to set inverse="true".

No. I have tested. It work.