OneToOne Mapping in Hibernate using Annotations

OneToOne Mapping in Hibernate using Annotations:

In this example lets see how to implement OneToOne mapping in hibernate using Annotations.

There are 3 types of Mappings in Hibernate,
1. OneToOne
2. ManyToOne
3.ManyToMany

Here lets see an example of OntToOne Mapping.

In our example we are going to have 2 entities Address and Employee.  When we enter the employee details there will a column that points to another table ID where the related address of that employee is stored.

Once you go through this example, you can understand clearly.

Structure:

hibernate.cfg.xml

<hibernate-configuration>
  <session-factory>
    <property name="hibernate.hbm2ddl.auto">update</property>
    <property name="hibernate.show_sql">true</property>  
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernateannotation</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">root</property>
    <mapping class="com.javainfinite.pojo.Employee"/>
    <mapping class="com.javainfinite.pojo.Address"/>
  </session-factory>
</hibernate-configuration>

NewHibernateUtil.java

package com.javainfinite.pojo;

import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.SessionFactory;

public class NewHibernateUtil {

    private static final SessionFactory sessionFactory;
    
    static {
        try {
            // Create the SessionFactory from standard (hibernate.cfg.xml) 
            // config file.
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Log the exception. 
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

Address.java

package com.javainfinite.pojo;

import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity

@Table(name="Address_Mapping")
public class Address implements Serializable {
    
    @Id
    @GeneratedValue
    private int address1;
    private String city;
    @Column(name="State_EMP")
    private String state;
    

    public int getAddress1() {
        return address1;
    }

    public void setAddress1(int address1) {
        this.address1 = address1;
    }
    

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }   
}

Employee.java

package com.javainfinite.pojo;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name="Employee_Mapping")
public class Employee {
    
    @Id
    @GeneratedValue
    @Column(name="Employee_ID")
    private int eid;
    @Column(name="Employee_Name")
    private String ename;
    @Column(name="Employee_Dept")
    private String edept;
    
    @OneToOne (cascade={CascadeType.ALL})
    @JoinColumn(name="Address_Joining")
    private Address address;

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
    

    public int getEid() {
        return eid;
    }

    public void setEid(int eid) {
        this.eid = eid;
    }
    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public String getEdept() {
        return edept;
    }

    public void setEdept(String edept) {
        this.edept = edept;
    }
    
}

Execution.java

package com.javainfinite.execution;

import com.javainfinite.pojo.Address;
import com.javainfinite.pojo.Employee;
import com.javainfinite.pojo.NewHibernateUtil;
import org.hibernate.Session;
import org.hibernate.Transaction;


public class Execution {
  public static void main(String args[])
    {
        Session session=NewHibernateUtil.getSessionFactory().openSession();
        Transaction trans=session.beginTransaction();
        
        Employee emp=new Employee();
        Address addr=new Address();

        emp.setEname("Alpha");
        emp.setEdept("Model");
        
        addr.setState("Venganza");
        addr.setCity("Veidsa");

        emp.setAddress(addr);
        
        session.save(emp);
        trans.commit();
    }
}

Output:

Employee Table

Here we can see that a new column “Address_Joining” has been included in table and it points to ID: 1 of Address table

Here we can see the address table with pointing id:1