Hibernate one-to-one unidirectional mapping using annotation

Hi friends,

Here i’m gonna tell you something about Hibernate mapping. I’m not exploring the core of hibernate Object Relational Mapping (ORM) tool. Let’s me come to the point.

I’m giving you an example of student and address. Since the relation is one to one, each student has exactly one address.

The DAO class looks like this, DAO.java.

package hba.dao;

import hba.util.HibernateUtil;
import org.hibernate.FlushMode;
import org.hibernate.Session;

public class DAO {

    private static final ThreadLocal THREAD = new ThreadLocal();

    protected DAO() {
    }

    public static Session getSession() {
        Session session = (Session) DAO.THREAD.get();
        if (session == null) {
            session = HibernateUtil.getSessionFactory().openSession();
            DAO.THREAD.set(session);
            getSession().setFlushMode(FlushMode.COMMIT);
        }
        return session;
    }

    protected static void begin() {
        getSession().beginTransaction();
    }

    protected static void commit() {
        getSession().getTransaction().commit();
    }

    protected static void rollback() {
        getSession().getTransaction().rollback();
        getSession().close();
        DAO.THREAD.set(null);
    }

    protected static void flush() {
        getSession().flush();
    }

    protected static void close() {
        getSession().close();
        DAO.THREAD.set(null);
    }
}

The hibernate configuration file, hibernate.cfb.xml.

<?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>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hba</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">password1.</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <mapping class="hba.pojo.o2o_u_student"/>
        <mapping class="hba.pojo.o2o_u_address"/>
    </session-factory>
</hibernate-configuration>

Here’s the student POJO, o2o_u_student.java.

package hba.pojo;

import java.io.Serializable;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "STUDENT", catalog = "hba")
public class o2o_u_student implements Serializable {

    private long std_id;
    private String std_name;
    private o2o_u_address std_address;

    @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "STD_ADD_ID")
    public o2o_u_address getStd_address() {
        return std_address;
    }

    public void setStd_address(o2o_u_address std_address) {
        this.std_address = std_address;
    }

    @Id
    @GeneratedValue
    @Column(name = "STD_ID")
    public long getStd_id() {
        return std_id;
    }

    public void setStd_id(long std_id) {
        this.std_id = std_id;
    }

    @Column(name = "STD_NAME", length = 20, nullable = false)
    public String getStd_name() {
        return std_name;
    }

    public void setStd_name(String std_name) {
        this.std_name = std_name;
    }
}

Download Student POJO

Here’s the address POJO, o2o_u_address.java.

package hba.pojo;

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

@Entity
@Table(name = "ADDRESS", catalog = "hba")
public class o2o_u_address implements Serializable {

    private long add_id;
    private String add_address;

    @Column(name = "ADD_ADDRESS", length = 50, nullable = false)
    public String getAdd_address() {
        return add_address;
    }

    public void setAdd_address(String add_address) {
        this.add_address = add_address;
    }

    @Id
    @Column(name = "ADD_ID")
    public long getAdd_id() {
        return add_id;
    }

    public void setAdd_id(long add_id) {
        this.add_id = add_id;
    }
}

Download address POJO

Finally, here’s the save() method.

public class o2o_u_std_add extends DAO {
public void save() {
        try {
            begin();
            o2o_u_student student = new o2o_u_student();
            o2o_u_address address = new o2o_u_address();
            address.setAdd_id(2);
            address.setAdd_address("Sydney Place, Washington, DC 20521-4150");
            student.setStd_name("deepesh");
            student.setStd_address(address);
            getSession().save(student);
            commit();
        } catch (Exception e) {
            rollback();
            System.out.println("Exception :" + e.getMessage() + "Cause :" + e.getCause());
        } finally {
            flush();
            close();
        }
    }

public static void main(String[] args) throws Exception {
        new o2o_u_std_add().save();
    }
}

Download save() method.

The output of the above save() method will be

Hibernate: select o2o_u_addr_.ADD_ID, o2o_u_addr_.ADD_ADDRESS as ADD2_1_ from hba.ADDRESS o2o_u_addr_ where o2o_u_addr_.ADD_ID=?
Hibernate: insert into hba.STUDENT (STD_ADD_ID, STD_NAME) values (?, ?)

Thank You.