Hibernate- One to One Unidirectional Mapping Annotation Example

Hibernate- One to One Unidirectional Mapping Annotation Example

We create Instructor and InstructorDetail entities and we make a one-to-one unidirectional mapping between them.

We will implement CRUD (create/save, read, update, delete) operations for Instructor and InstructorDetail entities.

For Instructor DAO CRUD operations:

voidsaveInstructor(Instructor instructor);

voidupdateInstructor(Instructor instructor);

voiddeleteInstructor(int id);

InstructorgetInstructor(int id);

For InstructorDetailDao DAO CRUD operations:

voidsaveInstructorDetail(InstructorDetailinstructorDetail);

voidupdateInstructorDetail(InstructorDetailinstructorDetail);

InstructorDetailgetInstructorDetail(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 How to Create a Simple Maven Project in Eclipse article to create a simple Maven project in Eclipse IDE.

2. Project Directory Structure

   Let’s create a packaging structure for the above created a simple maven project.

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.ducatindia.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>8.0.13< /version>
   < /dependency>
   < !-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
   < dependency>
   < groupId>org.hibernate< /groupId>
   < artifactId>hibernate-core< /artifactId>
   < version>5.3.7.Final< /version>
   < /dependency>
   < /dependencies>
   < build>
   < sourceDirectory>src/main/java< /sourceDirectory>
   < plugins>
   < plugin>
   < artifactId>maven-compiler-plugin< /artifactId>
   < version>3.5.1< /version>
   < configuration>
   < source>1.8< /source>
   < target>1.8< /target>
   < /configuration>
   < /plugin>
   < /plugins>
   < /build>
   < /project>
   

4. Creating the JPA Entities(Persistent classes)

   We are creating a unidirectional mapping, we have placed @OneToOne annotation on the Instructor entity so that the instuctor_detail_id will create in an instructor table.

   Instructor JPA Entity

   packagenet.ducatindia.hibernate.entity;
   
   importjavax.persistence.CascadeType;
   importjavax.persistence.Column;
   importjavax.persistence.Entity;
   importjavax.persistence.GeneratedValue;
   importjavax.persistence.GenerationType;
   importjavax.persistence.Id;
   importjavax.persistence.JoinColumn;
   importjavax.persistence.OneToOne;
   importjavax.persistence.Table;
   
   @Entity
   @Table(name="instructor")
   publicclassInstructor {
   
   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   @Column(name="id")
   privateint id;
   
   @Column(name="first_name")
   privateStringfirstName;
   
   @Column(name="last_name")
   privateStringlastName;
   
   @Column(name="email")
   privateString email;
   
   @OneToOne(cascade=CascadeType.ALL)
   @JoinColumn(name="instructor_detail_id")
   privateInstructorDetailinstructorDetail;
   
   publicInstructor() {
   
       }
   
   publicInstructor(StringfirstName, StringlastName, Stringemail) {
   this.firstName=firstName;
   this.lastName=lastName;
   this.email= email;
       }
   
   publicintgetId() {
   return id;
       }
   
   publicvoidsetId(intid) {
   this.id = id;
       }
   
   publicStringgetFirstName() {
   returnfirstName;
       }
   
   publicvoidsetFirstName(StringfirstName) {
   this.firstName=firstName;
       }
   
   publicStringgetLastName() {
   returnlastName;
       }
   
   publicvoidsetLastName(StringlastName) {
   this.lastName=lastName;
       }
   
   publicStringgetEmail() {
   return email;
       }
   
   publicvoidsetEmail(Stringemail) {
   this.email= email;
       }
   
   publicInstructorDetailgetInstructorDetail() {
   returninstructorDetail;
       }
   
   publicvoidsetInstructorDetail(InstructorDetailinstructorDetail) {
   this.instructorDetail=instructorDetail;
       }
   }
   

   InstructorDetail JPA Entity

   packagenet.ducatindia.hibernate.entity;
   
   importjavax.persistence.Column;
   importjavax.persistence.Entity;
   importjavax.persistence.GeneratedValue;
   importjavax.persistence.GenerationType;
   importjavax.persistence.Id;
   importjavax.persistence.Table;
   
   @Entity
   @Table(name="instructor_detail")
   publicclassInstructorDetail {
   
   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   @Column(name="id")
   privateint id;
   
   @Column(name="youtube_channel")
   privateStringyoutubeChannel;
   
   @Column(name="hobby")
   privateString hobby;
   
   publicInstructorDetail() {
   
       }
   
   publicInstructorDetail(StringyoutubeChannel, Stringhobby) {
   this.youtubeChannel=youtubeChannel;
   this.hobby= hobby;
       }
   
   publicintgetId() {
   return id;
       }
   
   publicvoidsetId(intid) {
   this.id = id;
       }
   
   publicStringgetYoutubeChannel() {
   returnyoutubeChannel;
       }
   
   publicvoidsetYoutubeChannel(StringyoutubeChannel) {
   this.youtubeChannel=youtubeChannel;
       }
   
   publicStringgetHobby() {
   return hobby;
       }
   
   publicvoidsetHobby(Stringhobby) {
   this.hobby= hobby;
       }
   }
   

5. Create Hibernate DAO Classes

   InstructorDao.java

   packagenet.ducatindia.hibernate.dao;
   
   importorg.hibernate.Session;
   importorg.hibernate.Transaction;
   
   importnet.ducatindia.hibernate.entity.Instructor;
   importnet.ducatindia.hibernate.util.HibernateUtil;
   
   publicclassInstructorDao {
   publicvoidsaveInstructor(Instructorinstructor) {
   Transactiontransaction=null;
   try (Sessionsession=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();
           }
       }
   
   publicvoidupdateInstructor(Instructorinstructor) {
   Transactiontransaction=null;
   try (Sessionsession=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();
           }
       }
   
   publicvoiddeleteInstructor(intid) {
   
   Transactiontransaction=null;
   try (Sessionsession=HibernateUtil.getSessionFactory().openSession()) {
   // start a transaction
   transaction=session.beginTransaction();
   
   // Delete a instructor object
   Instructorinstructor=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();
           }
       }
   
   publicInstructorgetInstructor(intid) {
   
   Transactiontransaction=null;
   Instructorinstructor=null;
   try (Sessionsession=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

   packagenet.ducatindia.hibernate.dao;
   
   importorg.hibernate.Session;
   importorg.hibernate.Transaction;
   
   importnet.ducatindia.hibernate.entity.InstructorDetail;
   importnet.ducatindia.hibernate.util.HibernateUtil;
   
   publicclassInstructorDetailDao {
   
   publicvoidsaveInstructorDetail(InstructorDetailinstructorDetail) {
   Transactiontransaction=null;
   try (Sessionsession=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();
           }
       }
   
   publicvoidupdateInstructorDetail(InstructorDetailinstructorDetail) {
   Transactiontransaction=null;
   try (Sessionsession=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();
           }
       }
   
   publicInstructorDetailgetInstructorDetail(intid) {
   
   Transactiontransaction=null;
   InstructorDetail instructor =null;
   try (Sessionsession=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. Create a Hibernate configuration file – 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.

   packagenet.ducatindia.hibernate.util;
   
   importjava.util.Properties;
   
   importorg.hibernate.SessionFactory;
   importorg.hibernate.boot.registry.StandardServiceRegistryBuilder;
   importorg.hibernate.cfg.Configuration;
   importorg.hibernate.cfg.Environment;
   importorg.hibernate.service.ServiceRegistry;
   
   importnet.ducatindia.hibernate.entity.Course;
   importnet.ducatindia.hibernate.entity.Instructor;
   
   /**
    * Java based configuration
    * @authorrajansingh
    *
    */
   publicclassHibernateUtil {
   privatestaticSessionFactorysessionFactory;
   
   publicstaticSessionFactorygetSessionFactory() {
   if (sessionFactory==null) {
   try {
   Configurationconfiguration=newConfiguration();
   
   // Hibernate settings equivalent to hibernate.cfg.xml's properties
   Properties settings =newProperties();
   settings.put(Environment.DRIVER, "com.mysql.cj.jdbc.Driver");
   settings.put(Environment.URL, "jdbc:mysql://localhost:3306/javafx_demo?useSSL=false");
   settings.put(Environment.USER, "root");
   settings.put(Environment.PASS, "root");
   settings.put(Environment.DIALECT, "org.hibernate.dialect.MySQL5InnoDBDialect");
   
   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(Instructor.class);
   configuration.addAnnotatedClass(Course.class);
   
   ServiceRegistryserviceRegistry=newStandardServiceRegistryBuilder()
                       .applySettings(configuration.getProperties()).build();
   System.out.println("Hibernate Java ConfigserviceRegistry created");
   sessionFactory=configuration.buildSessionFactory(serviceRegistry);
   returnsessionFactory;
   
               } catch (Exception e) {
   e.printStackTrace();
               }
           }
   returnsessionFactory;
       }
   }
   

7. Create the Main class and Run an Application

   packagenet.ducatindia.hibernate;
   
   importnet.ducatindia.hibernate.dao.InstructorDao;
   importnet.ducatindia.hibernate.entity.Instructor;
   importnet.ducatindia.hibernate.entity.InstructorDetail;
   
   publicclassManApp {
   publicstaticvoidmain(String[] args) {
   
   Instructorinstructor=newInstructor("Rajan", "Fadatare", "rajan@ducatinida.com");
   InstructorDetailinstructorDetail=newInstructorDetail("http://www.youtube.com", "Guitar");
   instructor.setInstructorDetail(instructorDetail);
   
   InstructorDaoinstructorDao=newInstructorDao();
   instructorDao.saveInstructor(instructor);
       }
   }
   

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