Meyyappan has posted 101 posts at DZone. View Full User Profile

Hibernate One-To-One Mapping Tutorial

06.14.2012
| 135272 views |
  • submit to reddit

In this example you will learn how to map one-to-one relationship using Hibernate. Consider the following relationship between Student and Address entity.

According to the relationship each student should have a unique address.

To create this relationship you need to have a STUDENT and ADDRESS table. The relational model is shown below.

To create the STUDENT and ADDRESS table you need to create the following hibernate mapping files.

Student.hbm.xml is used to create the STUDENT table.

<?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="com.vaannila.student.Student" table="STUDENT">
        <meta attribute="class-description">This class contains student details.</meta>
        <id name="studentId" type="long" column="STUDENT_ID">
            <generator class="native" />
        </id>
        <property name="studentName" type="string" not-null="true" length="100" column="STUDENT_NAME" />
        <many-to-one name="studentAddress" class="com.vaannila.student.Address" column="STUDENT_ADDRESS" not-null="true" cascade="all" unique="true" />
    </class>
</hibernate-mapping>

We use the many-to-one element to create the one-to-one relationship between the Student and Address entities. We do this my making the STUDENT_ADDRESS column unique in the STUDENT table.

Address.hbm.xml is used to create the ADDRESS table.

<?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="com.vaannila.student.Address" table="ADDRESS">
		<meta attribute="class-description">This class contains the student's address
			details.</meta>
		<id name="addressId" type="long" column="ADDRESS_ID">
			<generator class="native" />
		</id>
		<property name="street" column="ADDRESS_STREET" type="string" length="250" />
		<property name="city" column="ADDRESS_CITY" type="string" length="50" />
		<property name="state" column="ADDRESS_STATE" type="string" length="50" />
		<property name="zipcode" column="ADDRESS_ZIPCODE" type="string" length="10" />
	</class>
</hibernate-mapping>

Now create the hibernate configuration file and add all the mapping files.

<?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.connection.driver_class"> org.hsqldb.jdbcDriver </property>
        <property name="hibernate.connection.url"> jdbc:hsqldb:hsql://localhost</property>
        <property name="hibernate.connection.username">sa</property>
        <property name="connection.password"></property>
        <property name="connection.pool_size">1</property>
        <property name="hibernate.dialect"> org.hibernate.dialect.HSQLDialect </property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">create-drop</property>
        <mapping resource="com/vaannila/student/Student.hbm.xml"/>
        <mapping resource="com/vaannila/student/Address.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

After creating the configuration file, generate java class files using Hibernate Tools.(To generate code using Hibernate Tools refer this example )

The following classes will be generated.

package com.vaannila.student;

// Generated Sep 3, 2009 7:20:37 PM by Hibernate Tools 3.2.4.GA

/**
 * This class contains student details.
 */
public class Student implements java.io.Serializable {

	private long studentId;
	private String studentName;
	private Address studentAddress;

	public Student() {
	}

	public Student(String studentName, Address studentAddress) {
		this.studentName = studentName;
		this.studentAddress = studentAddress;
	}

	public long getStudentId() {
		return this.studentId;
	}

	public void setStudentId(long studentId) {
		this.studentId = studentId;
	}

	public String getStudentName() {
		return this.studentName;
	}

	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}

	public Address getStudentAddress() {
		return this.studentAddress;
	}

	public void setStudentAddress(Address studentAddress) {
		this.studentAddress = studentAddress;
	}

}
package com.vaannila.student;

// Generated Sep 3, 2009 7:20:37 PM by Hibernate Tools 3.2.4.GA

/**
 * This class contains the student's address
 * 			details.
 */
public class Address implements java.io.Serializable {

	private long addressId;
	private String street;
	private String city;
	private String state;
	private String zipcode;

	public Address() {
	}

	public Address(String street, String city, String state, String zipcode) {
		this.street = street;
		this.city = city;
		this.state = state;
		this.zipcode = zipcode;
	}

	public long getAddressId() {
		return this.addressId;
	}

	public void setAddressId(long addressId) {
		this.addressId = addressId;
	}

	public String getStreet() {
		return this.street;
	}

	public void setStreet(String street) {
		this.street = street;
	}

	public String getCity() {
		return this.city;
	}

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

	public String getState() {
		return this.state;
	}

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

	public String getZipcode() {
		return this.zipcode;
	}

	public void setZipcode(String zipcode) {
		this.zipcode = zipcode;
	}

}

Create the Main class to run the example.

package com.vaannila.student;

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

import com.vaannila.util.HibernateUtil;

public class Main {

	public static void main(String[] args) {
		Session session = HibernateUtil.getSessionFactory().openSession();
		Transaction transaction = null;
		try {
			transaction = session.beginTransaction();
			Address address1 = new Address("OMR Road", "Chennai", "TN", "600097");
			Address address2 = new Address("Ring Road", "Banglore", "Karnataka", "560000");
			Student student1 = new Student("Eswar", address1);
			Student student2 = new Student("Joe", address2);
			session.save(student1);
			session.save(student2);
			transaction.commit();
		} catch (HibernateException e) {
			transaction.rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}

	}

}

On executing the Main class you will see the following output.

The Student table has two records.

The Address table has two record.

Each student record points to a different address record, this illustrates the one-to-one mapping.

The folder structure of the example is shown below.

You can download the source code of this example here.

Source :Download
Published at DZone with permission of its author, Meyyappan Muthuraman.

(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)

Comments

Pawas Sharma replied on Mon, 2012/12/10 - 2:28pm

what do u mean by property in java?

Antonio Espinosa replied on Mon, 2013/06/24 - 3:39pm

 excuse me mr. i use netbeans and hibernate i guess the only change is the tools bundled to interact with hibernate but i follow your procedure and hibernate maps me a table relationship one to many, i use mysql with inodb engine (the persistence java class is created by a reverse engineering file ) where do you think i can find the problem? ( i don't want to write entities classes because it's slower and first i diagram the database wich is faster ) please help me

Amit Himani replied on Tue, 2013/07/02 - 6:17am

Thanks for very good article. Please help me understand use of antlr.jar, javassist.jar and self4j.jar.

I can run the code without using them. I might be missing some thing.

Divya Jeganathan replied on Tue, 2014/01/07 - 2:56am

Excellent Tutorial to learn Java.....

Know More About Java 

Akki Rocks replied on Wed, 2014/01/08 - 2:22am in response to: Pawas Sharma

any attribute of class is also known as property

Anoop St replied on Wed, 2014/02/26 - 5:07am

why many-to-one mapping is used, example says one-to-one mapping?

Dilesh Sahoo replied on Thu, 2014/04/24 - 6:11am

Since the example is about one to one mapping the tag has to be <one-to-one>.

Pradeep Yadav replied on Sun, 2014/06/15 - 4:54pm

thanks 

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.