Hibernate Many-To-Many Mapping Using Annotations Part -2

The @ManyToMany annotation is used to create the many-to-many relationship between the Studentand Course entities. The @JoinTable annotation is used to create the STUDENT_COURSE link table and @JoinColumn annotation is used to refer the linking columns in both the tables.

Course class is used to create the COURSE table.

package com.vaannila.student;

 

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.Table;

 

@Entity

@Table(name="COURSE")

public class Course {

 

private long courseId;

private String courseName;

 

public Course() {

}

 

public Course(String courseName) {

this.courseName = courseName;

}

 

@Id

@GeneratedValue

@Column(name="COURSE_ID")

public long getCourseId() {

return this.courseId;

}

 

public void setCourseId(long courseId) {

this.courseId = courseId;

}

 

@Column(name="COURSE_NAME", nullable=false)

public String getCourseName() {

return this.courseName;

}

 

public void setCourseName(String courseName) {

this.courseName = courseName;

}

 

}

Now create the hibernate configuration file with the Student and Course class mapping.

<?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"> org.hsqldb.jdbcDriver</property>

<property name="hibernate.connection.url"> jdbc:hsqldb:hsql://localhost<;/property>

<property name="hibernate.connection.username">sa</property>

<property name="connection.password"></property>

<property name="connection.pool_size">1</property>

<property name="hibernate.dialect"> org.hibernate.dialect.HSQLDialect</property>

<property name="show_sql">true</property>

<property name="hbm2ddl.auto">create-drop</property>

<mapping class="com.vaannila.student.Student" />

<mapping class="com.vaannila.student.Course" />

</session-factory>

</hibernate-configuration>

Create the Main class to run the example.

package com.vaannila.student;

 

import java.util.HashSet;

import java.util.Set;

 

import org.hibernate.HibernateException;

import org.hibernate.Session;

import org.hibernate.Transaction;

 

import com.vaannila.util.HibernateUtil;

 

public class Main {

 

public static void main(String[] args) {

 

Session session = HibernateUtil.getSessionFactory().openSession();

Transaction transaction = null;

try {

transaction = session.beginTransaction();

 

Set<Course> courses = new HashSet<Course>();

courses.add(new Course("Maths"));

courses.add(new Course("Computer Science"));

 

Student student1 = new Student("Eswar", courses);

Student student2 = new Student("Joe", courses);

session.save(student1);

session.save(student2);

 

transaction.commit();

} catch (HibernateException e) {

transaction.rollback();

e.printStackTrace();

} finally {

session.close();

}

 

}

}