Hibernate Many to One Mapping using XML

In many to one mapping, various attributes can be referred to one attribute only.

In this example, every employee has one company address only and one address belongs to many employees. Here, we are going to perform many to one mapping using XML.

1) Persistent classes for one to one mapping

There are two persistent classes Employee.java and Address.java. Employee class contains Address class reference and vice versa.

Employee.java

package com.javatpoint;  
  
public class Employee {  
private int employeeId;  
private String name,email;  
private Address address;  
//setters and getters  
}  

Address.java

package com.javatpoint;  
  
public class Address {  
private int addressId;  
private String addressLine1,city,state,country;  
private int pincode;  
private Employee employee;  
//setters and getters  
}

2) Mapping files for the persistent classes

The two mapping files are employee.hbm.xml and address.hbm.xml.

employee.hbm.xml

<?xml version='1.0' encoding='UTF-8'?>  
<!DOCTYPE hibernate-mapping PUBLIC  
          "-//Hibernate/Hibernate Mapping DTD 5.3//EN"  
          "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd">  
  
          <hibernate-mapping>  
          <class name="com.javatpoint.Employee" table="emp22">  
          <id name="employeeId">  
          <generator class="increment"></generator>  
          </id>  
          <property name="name"></property>  
          <property name="email"></property>  
            
          <many-to-one name="address" cascade="all"></many-to-one>  
          </class>  
            
          </hibernate-mapping> 

address.hbm.xml

<?xml version='1.0' encoding='UTF-8'?>  
<!DOCTYPE hibernate-mapping PUBLIC  
          "-//Hibernate/Hibernate Mapping DTD 5.3//EN"  
          "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd">  
  
          <hibernate-mapping>  
          <class name="com.javatpoint.Address" table="address22">  
          <id name="addressId">  
          <generator class="increment"></generator>  
          </id>  
          <property name="addressLine1"></property>  
          <property name="city"></property>  
          <property name="state"></property>  
          <property name="country"></property>  
          <property name="pincode"></property>  
          </class>  
          </hibernate-mapping>  

3) Configuration file

This file contains information about the database and mapping file.

<?xml version='1.0' encoding='UTF-8'?>  
<!DOCTYPE hibernate-configuration PUBLIC  
          "-//Hibernate/Hibernate Configuration DTD 5.3//EN"  
          "http://hibernate.sourceforge.net/hibernate-configuration-5.3.dtd">  
   
<hibernate-configuration>  
  
    <session-factory>  
        <property name="hbm2ddl.auto">update</property>  
        <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>  
        <property name="connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>  
        <property name="connection.username">system</property>  
        <property name="connection.password">jtp</property>  
        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>  
    <mapping resource="employee.hbm.xml"/>  
    <mapping resource="address.hbm.xml"/>  
    </session-factory>  
  
</hibernate-configuration>  

4) User classes to store and fetch the data

Store.java

package com.javatpoint;  

import org.hibernate.*;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;  
  
public class Store {  
public static void main(String[] args) {  
	
	StandardServiceRegistry ssr=new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build();
	Metadata meta=new MetadataSources(ssr).getMetadataBuilder().build();
	
	SessionFactory factory=meta.getSessionFactoryBuilder().build();
	Session session=factory.openSession();
	
    Transaction t=session.beginTransaction();  
      
    Employee e1=new Employee();  
    e1.setName("Ravi Malik");  
    e1.setEmail("ravi@gmail.com");  
    
    Employee e2=new Employee();
    e2.setName("Anuj Verma");
    e2.setEmail("anuj@gmail.com");
      
    Address address1=new Address();  
    address1.setAddressLine1("G-13,Sector 3");  
    address1.setCity("Noida");  
    address1.setState("UP");  
    address1.setCountry("India");  
    address1.setPincode(201301);  
      
    e1.setAddress(address1);  
    e2.setAddress(address1);

    session.persist(e1);  
    session.persist(e2);
    t.commit();  
      
    session.close();  
    System.out.println("success");  
}  
}  

Output

Fetch.java

package com.javatpoint;  
import java.util.Iterator;  
import java.util.List;

import javax.persistence.TypedQuery;  
import org.hibernate.Session;  
import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder; 
  
public class Fetch {  
public static void main(String[] args) {  
	StandardServiceRegistry ssr=new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build();
	Metadata meta=new MetadataSources(ssr).getMetadataBuilder().build();
	
	SessionFactory factory=meta.getSessionFactoryBuilder().build();
	Session session=factory.openSession();
      
    TypedQuery query=session.createQuery("from Employee e");  
    List<Employee> list=query.getResultList(); 
      
    Iterator<Employee> itr=list.iterator();  
    while(itr.hasNext()){  
     Employee emp=itr.next();  
     System.out.println(emp.getEmployeeId()+" "+emp.getName()+" "+emp.getEmail());  
     Address address=emp.getAddress();  
     System.out.println(address.getAddressLine1()+" "+address.getCity()+" "+  
        address.getState()+" "+address.getCountry()+" "+address.getPincode());  
    }  
  
    session.close();  
    System.out.println("success");  
}  
}  