Basic Hibernate Mapping:

1. One to one mapping

One to one mapping is performed by one-to-one element. No foreign key is created in primary table. Let us see one simple example, in which we are using bidirectional association.

There are two persistent classes Student.java & Address.java. Student class contain Address class reference and vice versa

Student.java

package com.hibernateExample;  

public class Student {  
private int studentId;  
private String name,email;  
private Address address; 
}

Address.java

package com.hibernateExample;  

public class Address {  
private int addressId;  
private String addressLine1,city,state,country;  
private int pincode;  
private Student student;  

There are two mapping files for the persistent classes namely, student.hbm.xml & address.hbm.xml

In the mapping files, we are using one-to-one element.

student.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.hibernateExample.Student" table="student">  
          <id name="studentId">  
          <generator class="increment"></generator>  
          </id>  
          <property name="name"></property>  
          <property name="email"></property>  

          <one-to-one name="address" cascade="all"></one-to-one>  
          </class>  

          </hibernate-mapping>  

address.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.hibernateExample.Address" table="address">  
          <id name="addressId">  
          <generator class="foreign">  
          <param name="property">student</param>  
          </generator>  
          </id>  
          <property name="addressLine1"></property>  
          <property name="city"></property>  
          <property name="state"></property>  
          <property name="country"></property>  

          <one-to-one name="student"></one-to-one>  
          </class>  

          </hibernate-mapping>  

A configuration file named hibernate.cfg.xml contains information about the database and mapping file.

<!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="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">oracle</property>  
        <property name="connection.driver&#95;class">oracle.jdbc.driver.OracleDriver</property>  
    <mapping resource="student.hbm.xml"/>  
    <mapping resource="address.hbm.xml"/>  
    </session-factory>  

</hibernate-configuration> 

To store the data :

..........................................
.........................................


 Student st1=new Student();  
        st1.setName("RaviShekar");  
        st1.setEmail("ravi12@gmail.com");  

        Address address1=new Address();  
        address1.setAddressLine1("A-22,vikas nagar");  
        address1.setCity("Ghaziabad");  
        address1.setState("UP");  
        address1.setCountry("India");  
        address1.setPincode(201301);  


        st1.setAddress(address1);  
        address1.setStudent(st1);  

        session.persist(st1);


  ...............................................
  ................................................

To fetch the data :

       ...........................................
       ........................................

       Query query=session.createQuery("from Student s");  
        List list=query.list();  

        Iterator itr=list.iterator();  
         while(itr.hasNext()){  
         Student stu=itr.next();  
         Address address=stu.getAddress();  
   .......................................
   ...............................................

Hope it helps someone!