Fetch Data using One To One Relationship in Hibernate 5

Java Libraries

Copy JAR files which are listed below:

antlr-2.7.7.jar
classmate-1.3.4.jar
commons-lang3-3.6.jar
commons-logging-1.1.3.jar
dom4j-1.6.1.jar
ehcache-core-2.6.11.jar
geolatte-geom-1.1.0.jar
hibernate-commons-annotations-5.0.1.Final.jar
hibernate-core-5.2.11.Final.jar
hibernate-ehcache-5.2.12.Final.jar
hibernate-ejb3-persistence.jar
hibernate-enhance-maven-plugin-4.3.7.Final.jar
hibernate-entitymanager.jar
hibernate-java8-5.2.11.Final.jar
hibernate-jpa-2.1-api-1.0.0.Final.jar
hibernate-spatial-5.2.11.Final.jar
hibernate-validator-6.0.2.Final.jar
javassist-3.16.1-GA.jar
jboss-logging-3.3.1.Final.jar
jboss-transaction-api_1.1_spec-1.0.1.Final.jar
jts-1.11.jar
mysql-connector-java-5.1.36.jar
slf4j-api-1.7.21.jar

Create Database

Create a database with the name is hibernate5. This database have 2 tables: Employee table and EmployeeCard table. Employee table and EmployeeCard table have a One to One. One employee have one card and One card belongs to one and only one employee.

--
-- Table structure for table `employee`
--

CREATE TABLE `employee` (
  `id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `username` varchar(250) NOT NULL,
  `password` varchar(250) NOT NULL,
  `status` tinyint(1) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- Dumping data for table `employee`
--

INSERT INTO `employee` (`username`, `password`, `status`) VALUES VALUES('e1', '123', 1);
INSERT INTO `employee` (`username`, `password`, `status`) VALUES VALUES('e2', '456', 1);

--
-- Table structure for table `employeecard`
--

CREATE TABLE `employeecard` (
  `employeeId` int(11) NOT NULL PRIMARY KEY,
  `cardNumber` varchar(250) NOT NULL,
  FOREIGN KEY (`employeeId`) REFERENCES `employee` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- Dumping data for table `employeecard`
--
INSERT INTO `employeecard` (`employeeId`, `cardNumber`) VALUES(1, '111');
INSERT INTO `employeecard` (`employeeId`, `cardNumber`) VALUES(2, '222');

Structure of Employee Table

Employee Table

Structure of Employee Card Table

Employee Card Table

Entities Class

Create two entities classes – Employee.java and EmployeeCard.java, to represent the above tables

Employee.java

package entities;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = "employee")
public class Employee implements java.io.Serializable {

	private Integer id;
	private String username;
	private String password;
	private boolean status;
	private EmployeeCard employeecard;

	public Employee() {
	}

	public Employee(String username, String password, boolean status) {
		this.username = username;
		this.password = password;
		this.status = status;
	}

	public Employee(String username, String password, boolean status, EmployeeCard employeecard) {
		this.username = username;
		this.password = password;
		this.status = status;
		this.employeecard = employeecard;
	}

	@Id
	@GeneratedValue(strategy = IDENTITY)
	@Column(name = "id", unique = true, nullable = false)
	public Integer getId() {
		return this.id;
	}

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

	@Column(name = "username", nullable = false, length = 250)
	public String getUsername() {
		return this.username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	@Column(name = "password", nullable = false, length = 250)
	public String getPassword() {
		return this.password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

	@Column(name = "status", nullable = false)
	public boolean isStatus() {
		return this.status;
	}

	public void setStatus(boolean status) {
		this.status = status;
	}

	@OneToOne(fetch = FetchType.LAZY, mappedBy = "employee")
	public EmployeeCard getEmployeecard() {
		return this.employeecard;
	}

	public void setEmployeecard(EmployeeCard employeecard) {
		this.employeecard = employeecard;
	}

}

EmployeeCard.java

package entities;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name = "employeecard")
public class EmployeeCard implements java.io.Serializable {

	private int employeeId;
	private Employee employee;
	private String cardNumber;

	public EmployeeCard() {
	}

	public EmployeeCard(Employee employee, String cardNumber) {
		this.employee = employee;
		this.cardNumber = cardNumber;
	}

	@GenericGenerator(name = "generator", strategy = "foreign", parameters = @Parameter(name = "property", value = "employee"))
	@Id
	@GeneratedValue(generator = "generator")

	@Column(name = "employeeId", unique = true, nullable = false)
	public int getEmployeeId() {
		return this.employeeId;
	}

	public void setEmployeeId(int employeeId) {
		this.employeeId = employeeId;
	}

	@OneToOne(fetch = FetchType.LAZY)
	@PrimaryKeyJoinColumn
	public Employee getEmployee() {
		return this.employee;
	}

	public void setEmployee(Employee employee) {
		this.employee = employee;
	}

	@Column(name = "cardNumber", nullable = false, length = 250)
	public String getCardNumber() {
		return this.cardNumber;
	}

	public void setCardNumber(String cardNumber) {
		this.cardNumber = cardNumber;
	}

}

Hibernate Configuration File

Puts Employee.java and EmployeeCard.java in your Hibernate configuration file, and also MySQL connection details.

<?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.enable_lazy_load_no_trans">true</property>
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.password">123456</property>
		<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate5</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.dialect">org.hibernate.spatial.dialect.mysql.MySQLSpatialDialect</property>
		<property name="hibernate.current_session_context_class">thread</property>
		<mapping class="entities.Employee" />
		<mapping class="entities.EmployeeCard" />
	</session-factory>
</hibernate-configuration>

Create HibernateUtil class

The HibernateUtil class helps in creating the SessionFactory from the Hibernate configuration file. The SessionFactory is threadsafe, so it is not necessary to obtain one for each thread.

package fetch_data;

import org.hibernate.*;
import org.hibernate.boot.*;
import org.hibernate.boot.registry.*;

public class HibernateUtil {

	private static final SessionFactory sessionFactory;

	static {
		try {
			StandardServiceRegistry standardRegistry = new
					StandardServiceRegistryBuilder()
					.configure("hibernate.cfg.xml")
					.build();
			Metadata metaData = new MetadataSources(
					standardRegistry)
					.getMetadataBuilder()
					.build();
			sessionFactory = metaData.getSessionFactoryBuilder().build();
		} catch (Throwable th) {
			throw new ExceptionInInitializerError(th);
		}
	}

	public static SessionFactory getSessionFactory() {
		return sessionFactory;

	}
}

Create EmployeeModel class

The EmployeeModel class contains methods to interact with the database.

package fetch_data;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import entities.Employee;

public class EmployeeModel {

	private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

	public Employee find(int id) {
		Employee employee = null;
		Session session = null;
		Transaction transaction = null;
		try {
			session = sessionFactory.openSession();
			transaction = session.beginTransaction();
			org.hibernate.query.Query query = session.createQuery("from Employee where id = :id");
			query.setParameter("id", id);
			employee = (Employee) query.uniqueResult();
			transaction.commit();
		} catch (Exception e) {
			employee = null;
			if (transaction != null) {
				transaction.rollback();
			}
		} finally {
			session.close();
		}
		return employee;
	}

}

Run It

package fetch_data;

import entities.Employee;

public class Main {

	public static void main(String[] args) {

		EmployeeModel employeeModel = new EmployeeModel();
		Employee employee = employeeModel.find(1);
		System.out.println("Employee Info");
		System.out.println("Id: " + employee.getId());
		System.out.println("Username: " + employee.getUsername());
		System.out.println("Status: " + employee.isStatus());
		System.out.println("Card Number: " + employee.getEmployeecard().getCardNumber());

	}

}

Output

Employee Info
Id: 1
Username: e1
Status: true
Card Number: 111