In this example we are describing one-to-many relation. There are two table one is Faculty and other is Subject.

Faculty Table

Facultyi_Id Faculty_Name
1 Neelesh
2 Remu
3 Kripa

Subject Table

Subject_Id Subject_Name
1 c
2 c++
3 Java
4 VB
5 Dotnet

Bridge Table i.e  Facult_Subject

Faculty_Id

Subject_Id

1 1
1 2
2 3
2 4
2 5

In a College  suppose different subjects can assign to one faculty but that same subject can't assign to different faculty. This is an one-to-many relationship.  In this example we have shown facuty_id no 1 has assigned two subjects i.e  c and c++, faculty_id no 2 - one subject java and so on. The Bridge table contains  Faculty_id and Subject_id. This can be achieve by many-to-many mapping but we have to add one more attribute i,e unique="true"

TO achiving this relation we have to follow these steps

Step1: Create  Faculty and Subject class

Faculty.java

```package com.bullraider.onetomany;
import java.util.HashSet;
import java.util.Set;
public class Faculty {
private long id;
private String name;
private Set<Subject> subjects=new HashSet<Subject>(0);
public Faculty(String name) {
super();
this.name = name;

}
public Set<Subject> getSubjects() {
return subjects;
}
public void setSubjects(Set<Subject> subjects) {
this.subjects = subjects;
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

}

```

Subject.java

```package com.bullraider.onetomany;
public class Subject {
private long id;
private String name;
public Subject(String name) {
super();
this.name = name;
}

public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

```

Step2: Create Faculty.hbm.xml and Subject.hb.xml

Faculty.hbm.xml

```<?xml version="1.0" encoding="UTF-8"?>
<!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.bullraider.onetomany.Faculty" table="Faculty">
<meta attribute="class-description"> This class contains Faculties details. </meta>
<id name="id" type="long" column="id">
<generator class="native" />
</id>
<property name="name" type="string" not-null="true" />
<key column="faculty_Id" />
<many-to-many column="subject_Id" class="com.bullraider.onetomany.Subject" unique="true"/>
</set>
</class>
</hibernate-mapping>

```

Subject.hbm.xml

```<?xml version="1.0" encoding="UTF-8"?>
<!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.bullraider.onetomany.Subject" table="subject">
<meta attribute="class-description"> This class contains policy details. </meta>
<id name="id" type="long" column="id">
<generator class="native" />
</id>
<property name="name" type="string" not-null="true" />
</class>
</hibernate-mapping>

Step3: Create Configuration file

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">oracle.jdbc.OracleDriver</property>
<property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:ORCL</property>
<property name="connection.pool_size">1</property>
<property name="hibernate.dialect">org.hibernate.dialect.OracleDialect</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">create-drop</property>
<mapping resource="com/bullraider/manytomany/Subject.hbm.xml"/>
<mapping resource="com/bullraider/manytomany/Faculty.hbm.xml"/>
</session-factory>
</hibernate-configuration>

```

step4: Create HibernateUtil class to get SessionFactory Object

```package com.bullraider.manytomany;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
private static final SessionFactory sessionFactory;
static {
try {
sessionFactory = new Configuration().configure()
.buildSessionFactory();
} catch (Throwable ex) {
System.err.println("SessionFactory creation failed" + ex);
throw new ExceptionInInitializerError(ex);
}
}

public static SessionFactory getSessionFactory() {
return sessionFactory;
}
}

```

step5: Create One Main Class for adding opertions.

```package com.bullraider.onetomany;
import java.util.HashSet;
import java.util.Set;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.bullraider.onetomany.util.HibernateUtil;
public class Main {

public static void main(String[] args) {
Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction = null;
try {
transaction = session.beginTransaction();
Set<Subject> subject= new HashSet<Subject>();
Faculty fc1=new Faculty("Srinivas");
fc1.setSubjects(subject);
session.save(fc1);
transaction.commit();
System.out.println("Records inserted sucessessfully");
} catch (HibernateException e) {
transaction.rollback();
e.printStackTrace();
} finally {
session.close();
}

}
}

```

Note:

```<set name="subjects" table="subject_faculty" cascade="all" >
<key column="faculty_Id" />
<many-to-many column="subject_Id" class="com.bullraider.o2m.Subject" unique="true"/>
</set>

```

Here we are creating Bridge table "subject_faculty" having attribute "faculty_Id" ,"subject_Id.