Check Out my Top 20 Udemy Courses with 75-80% Discount: Grab the Deal 🎯

Hibernate One to One Mapping CRUD Example

Author:

🎓 Top 15 Udemy Courses (80-90% Discount): My Udemy Courses - Ramesh Fadatare — All my Udemy courses are real-time and project oriented courses.

▶️ Subscribe to My YouTube Channel (178K+ subscribers): Java Guides on YouTube

▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube

In this tutorial, we implement one-to-one bidirectional entity mapping using JPA, Hibernate, and MySQL databases. We will perform CRUD ( Create, Read, Update, and Delete) operations with the MySQL database.
In this example, we create Instructor and InstructorDetail entities and we make a one-to-one mapping between them.
We will implement CRUD (create/save, read, update, delete) operations for Instructor and InstructorDetailentities.
For Instructor DAO CRUD operations:
void saveInstructor(Instructor instructor); void updateInstructor(Instructor instructor); void deleteInstructor(int id); Instructor getInstructor(int id);
For InstructorDetailDao DAO CRUD operations:
void saveInstructorDetail(InstructorDetail instructorDetail); void updateInstructorDetail(InstructorDetail instructorDetail); InstructorDetail getInstructorDetail(int id);

Development Steps

  1. Create a Simple Maven Project
  2. Project Directory Structure
  3. Add jar Dependencies to pom.xml
  4. Creating the JPA Entities(Persistent classes)
  5. Create Hibernate DAO Classes
  6. Create a Hibernate configuration file - HibernateUtil.java (Java Configuration)
  7. Create the Main class and Run an Application

1. Create a Simple Maven Project

Use the How to Create a Simple Maven Project in Eclipse article to create a simple Maven project in Eclipse IDE.

2. Project Directory Structure

Refer to the below screenshot to create a project or packaging structure for our Hibernate application:


3. Add dependencies to pom.xml

We are using MySQL database so add MySQL dependency to pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>net.javaguides.hibernate</groupId> <artifactId>hibernate-tutorial</artifactId> <version>0.0.1-SNAPSHOT</version> </parent> <artifactId>hibernate-one-to-one-example</artifactId> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.32</version> </dependency> <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>6.1.7.Final</version> </dependency> </dependencies> <build> <sourceDirectory>src/main/java</sourceDirectory> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.5.1</version> <configuration> <source>17</source> <target>17</target> </configuration> </plugin> </plugins> </build> </project>
Note that we are using the mysql-connector-java driver dependency to connect the Java Hibernate application to the MySQL database:
 <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.32</version> </dependency>
We are using Hibernate core dependency:
 <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>6.1.7.Final</version> </dependency>
We are using the maven-compiler-plugin to compile the Java Hibernate application with JRE 17 version:
 <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.5.1</version> <configuration> <source>17</source> <target>17</target> </configuration> </plugin>

4. Creating the JPA Entities(Persistent classes)

We are creating a bidirectional mapping, we will place @OneToOne annotation on both entity classes.

Instructor JPA Entity

package net.javaguides.hibernate.entity; import jakarta.persistence.*; @Entity @Table(name = "instructor") public class Instructor { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id") private int id; @Column(name = "first_name") private String firstName; @Column(name = "last_name") private String lastName; @Column(name = "email") private String email; @OneToOne(cascade = CascadeType.ALL, mappedBy = "instructor", fetch = FetchType.LAZY) private InstructorDetail instructorDetail; public Instructor() { } public Instructor(String firstName, String lastName, String email) { this.firstName = firstName; this.lastName = lastName; this.email = email; } // getters and setters }

InstructorDetail JPA Entity

package net.javaguides.hibernate.entity; import jakarta.persistence.*; @Entity @Table(name = "instructor_detail") public class InstructorDetail { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "id") private int id; @Column(name = "youtube_channel") private String youtubeChannel; @Column(name = "hobby") private String hobby; @OneToOne(fetch = FetchType.LAZY) @JoinColumn(name = "instructor_id") private Instructor instructor; public InstructorDetail() { } public InstructorDetail(String youtubeChannel, String hobby) { this.youtubeChannel = youtubeChannel; this.hobby = hobby; } // getters and setters }
Note that we are using the below JPA annotations:
  • @Table maps the entity with the table. If no @Table is defined, the default value is used: the class name of the entity.
  • @Entity - This annotation specifies that the class is an entity. 
  • @Id declares the identifier property of the entity.
  • @Column maps the entity's field with the table's column. If @Column is omitted, the default value is used: the field name of the entity.
  • @GeneratedValue - This annotation specifies the generation strategies for the values of primary keys.
  • @OneToOne - The @OneToOne annotation is used to specify a one-to-one database relationship.

5. Create Hibernate DAO Classes

InstructorDao.java

Let's create InstructorDao class and add the following code to it:
package net.javaguides.hibernate.dao; import org.hibernate.Session; import org.hibernate.Transaction; import net.javaguides.hibernate.entity.Instructor; import net.javaguides.hibernate.util.HibernateUtil; public class InstructorDao { public void saveInstructor(Instructor instructor) { Transaction transaction = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // save the student object session.save(instructor); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } } public void updateInstructor(Instructor instructor) { Transaction transaction = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // save the student object session.update(instructor); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } } public void deleteInstructor(int id) { Transaction transaction = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // Delete a instructor object Instructor instructor = session.get(Instructor.class, id); if (instructor != null) { session.delete(instructor); System.out.println("instructor is deleted"); } // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } } public Instructor getInstructor(int id) { Transaction transaction = null; Instructor instructor = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // get an instructor object instructor = session.get(Instructor.class, id); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } return instructor; } }

InstructorDetailDao.java

Let's create InstructorDetailDao class and add the following code to it:
package net.javaguides.hibernate.dao; import org.hibernate.Session; import org.hibernate.Transaction; import net.javaguides.hibernate.entity.InstructorDetail; import net.javaguides.hibernate.util.HibernateUtil; public class InstructorDetailDao { public void saveInstructorDetail(InstructorDetail instructorDetail) { Transaction transaction = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // save the student object session.save(instructorDetail); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } } public void updateInstructorDetail(InstructorDetail instructorDetail) { Transaction transaction = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // save the student object session.update(instructorDetail); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } } public InstructorDetail getInstructorDetail(int id) { Transaction transaction = null; InstructorDetail instructor = null; try (Session session = HibernateUtil.getSessionFactory().openSession()) { // start a transaction transaction = session.beginTransaction(); // get an instructor object instructor = session.get(InstructorDetail.class, id); // commit transaction transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } return instructor; } }

6. HibernateUtil.java (Java Configuration)

The HibernateUtil Java configuration file contains information about the database and mapping file. Let's create a HibernateUtil file and write the following code in it.
package net.javaguides.hibernate.util; import java.util.Properties; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; import org.hibernate.cfg.Environment; import org.hibernate.service.ServiceRegistry; import net.javaguides.hibernate.entity.Instructor; import net.javaguides.hibernate.entity.InstructorDetail; /**  * Java based configuration  * @author ramesh Fadatare  *  */ public class HibernateUtil { private static SessionFactory sessionFactory; public static SessionFactory getSessionFactory() { if (sessionFactory == null) { try { Configuration configuration = new Configuration(); // Hibernate settings equivalent to hibernate.cfg.xml's properties Properties settings = new Properties(); settings.put(Environment.DRIVER, "com.mysql.cj.jdbc.Driver"); settings.put(Environment.URL, "jdbc:mysql://localhost:3306/hibernate_db"); settings.put(Environment.USER, "root"); settings.put(Environment.PASS, "root"); settings.put(Environment.SHOW_SQL, "true"); settings.put(Environment.CURRENT_SESSION_CONTEXT_CLASS, "thread"); settings.put(Environment.HBM2DDL_AUTO, "create-drop"); configuration.setProperties(settings); configuration.addAnnotatedClass(InstructorDetail.class); configuration.addAnnotatedClass(Instructor.class); ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder() .applySettings(configuration.getProperties()).build(); System.out.println("Hibernate Java Config serviceRegistry created"); sessionFactory = configuration.buildSessionFactory(serviceRegistry); return sessionFactory; } catch (Exception e) { e.printStackTrace(); } } return sessionFactory; } }

7. Create the Main class and Run an Application

package net.javaguides.hibernate; import net.javaguides.hibernate.dao.InstructorDao; import net.javaguides.hibernate.entity.Instructor; import net.javaguides.hibernate.entity.InstructorDetail; public class ManApp { public static void main(String[] args) { Instructor instructor = new Instructor("Ramesh", "Fadatare", "ramesh@javaguides.com"); InstructorDetail instructorDetail = new InstructorDetail("http://www.youtube.com", "Guitar"); // associate the objects instructorDetail.setInstructor(instructor); // associate the objects instructor.setInstructorDetail(instructorDetail); // when you get instructorDetail then hibernate also saves instructor info InstructorDao instructorDao = new InstructorDao(); instructorDao.saveInstructor(instructor); } }
Note that when you save instructorDetail then hibernate also saves instructor info because of cascade and bidirectional mapping.

Output

Conclusion

In this tutorial, we successfully built a Hibernate project from scratch and learned how to map a one-to-one database relationship using JPA, Hibernate 6, and MySQL database.

Comments

Post a Comment

Leave Comment

Spring Boot 3 Paid Course Published for Free
on my Java Guides YouTube Channel

Subscribe to my YouTube Channel (165K+ subscribers):
Java Guides Channel

Top 10 My Udemy Courses with Huge Discount:
Udemy Courses - Ramesh Fadatare