Java Tutorial Blog

Many-to-One Relationship in Hibernate Mappings – Example

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This example program demonstrates how to write the many-to-one accociations using the hibernate mapping files.

Book.java

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package hibernate;
 
import java.io.Serializable;
 
public class Book implements Serializable{
	private long id;
	private String title;
	private Publisher publisher;
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public Publisher getPublisher() {
		return publisher;
	}
	public void setPublisher(Publisher publisher) {
		this.publisher = publisher;
	}
 
}

Publisher.java

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package hibernate;
 
import java.io.Serializable;
 
public class Publisher implements Serializable{
	private long id;
	private String 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;
	}
 
}

HibernateExample.java

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package hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
 
/**
 * source : www.javabeat.net
 */
public class HibernateExample {
    public static void main(String args[]){
        Configuration configuration = new Configuration();
        SessionFactory  sessionFactory = configuration.configure().buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        Publisher publisher = new Publisher();
        publisher.setName("First");
        session.save(publisher);
        transaction.commit();
        transaction = session.beginTransaction();
        Book book = new Book();
        book.setTitle("Test");
        book.setPublisher(publisher);
        session.save(book);
        transaction.commit();
        session.close();
    }
}

Book.hbm.xml

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<?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="hibernate.Book" table="Book">
        <id name="id" column="id" type="java.lang.Long" >
        	<generator class="increment"/>
        </id>
        <property name="title" column="title" type="java.lang.String"/>
        <many-to-one name="publisher" class="hibernate.Publisher" column="publisher"/>
    </class>
</hibernate-mapping>

Publisher.hbm.xml

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<?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="hibernate.Publisher" table="Publisher">
        <id name="id" column="id" type="java.lang.Long">
        	<generator class="increment"/>
        </id>
        <property name="name" column="name" type="java.lang.String"/>
    </class>
</hibernate-mapping>

hibernate.cfg.xml

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<?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>
        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/SampleDB</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
 
        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>
 
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
 
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
 
        <!-- Mapping files -->
        <mapping  resource="Publisher.hbm.xml"/>
        <mapping  resource="Book.hbm.xml"/>
    </session-factory>
</hibernate-configuration>