Hibernate one-to-one relationships

Hibernate Mapping One-to-One

Hibernate provides facility of mapping. You can do mapping through hbm.xml or through annotation. here is an example showing one to one relationship using hbm.xml.

We have two table ?

1.Customer(id,name)

2.Invoice(id,another_field)

Steps to cover this example as-

1.put hibernate library in to lib folder in src.

2.Create getter-setter of table.

Customer.java

package net.roseindia.table;
public class Customer {

    private int id;

    private String custName;

    private Invoice invoice;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getCustName() {
        return custName;
    }

    public void setCustName(String custName) {
        this.custName = custName;
    }

    public Invoice getInvoice() {
        return invoice;
    }

    public void setInvoice(Invoice invoice) {
        this.invoice = invoice;
    }

}

Invoice.java

package net.roseindia.table;

public class Invoice {

    private int id;

    private String anotherField;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAnotherField() {
        return anotherField;
    }

    public void setAnotherField(String anotherField) {
        this.anotherField = anotherField;
    }

}

Now map the tables by using hbm.xml.Each table has its own hbm.xml.

Customer.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="net.roseindia.table.Customer" table="Customer">
        <id name="id" type="int" column="Cus_id">
            <generator class="native" />
        </id>
        <property name="custName" type="java.lang.String" column="custName" />

        <many-to-one name="invoice" class="net.roseindia.table.Invoice"
            column="id" not-null="true" cascade="all" unique="true" />
    </class>
</hibernate-mapping>

Invoice.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="net.roseindia.table.Invoice" table="Invoice">
        <id name="id" type="int" column="id">
            <generator class="native" />
        </id>
        <property name="anotherField" type="java.lang.String" column="anotherField" />
    </class>
</hibernate-mapping>

Next step -

3. hibernate-cfg.xml is configuration file saved in the same folder where the source code of class file is saved. It creates the connection pool and set-up required environment.

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernateRelationShip</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.connection.pool_size">10</property>
        <property name="show_sql">true</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.hbm2ddl.auto">create-drop</property>

        <!-- Mapping files -->
        <mapping resource="Invoice.hbm.xml" />
        <mapping resource="Customer.hbm.xml" />

    </session-factory>
</hibernate-configuration>

4. Now create an util class as HibernateUtil.java package net.roseindia.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static SessionFactory sessionFactory = null;
    static {
        sessionFactory = new Configuration().configure().buildSessionFactory();
    }

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

Continue....

Here is next step- 5 Here is your main class.

package net.roseindia.application;

import net.roseindia.table.Customer;
import net.roseindia.table.Invoice;
import net.roseindia.util.HibernateUtil;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

public class OneToOneRelation {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        SessionFactory sessFact = null;
        Session session = null;
        try {
            session = HibernateUtil.getSessionFactory().openSession();

            // Create Customer Object
            Customer cust = new Customer();
            // /cust.setId(1);
            cust.setCustName("Ratna");
            // Invoice object
            Invoice inv = new Invoice();
            // Set some values in invoice
            inv.setAnotherField("Ratna Invoice");

            cust.setInvoice(inv);// Set invoice object to customer object
            Transaction tr = session.beginTransaction();
            session.save(cust);
            tr.commit();

            System.out.println("Done");

        } catch (HibernateException he) {
            System.out.println(he.getMessage());
        } finally {
            // SessionFactory close
             session.close();
        }

    }

}

Description: For creating one to one relationship we use many-to-one element. We can achieve this by making Invoice column unique in the Customer.