Topic 5- Working with Persistent Objects

Play Store Application link – Hibernate – in 10 steps – Apps on Google Play

Github project link (XML version) – https://github.com/kuldeep101990/HibernateSimpleCrud

Github project link (Annotation version)- https://github.com/kuldeep101990/HibernateSimpleCrudAnnotated

Here we are going to perform following operations-

Saving objects
Retrieving objects
Updating objects
Deleting objects

First, we will configure everything which will be needed-

1- Class (which need to be saved/updated/deleted and retrieved.
2- Hibernate Configuration file
3- Hibernate Mapping File
4- Create the Hibernate SessionFactory object
5- Open a Hibernate session

1- Class, we going to use for all above operations is below-

import java.util.Date;

public class Person {
 
    private long id;
    private String name;
    private Date dob;
 
    public Person() {
    }
 
    public Person(String name, Date dob) {
        this.name = name;
        this.dob = dob;
    }
 
    // getters and setters
 
    public long getId() {
        return id;
    }
 
    public void setId(long id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Date getDob() {
        return dob;
    }
 
    public void setDob(Date dob) {
        this.dob = dob;
    }
 
}

2- Hibernate configuration file

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/testdb</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">password</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        <mapping resource="Person.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

3- Hibernate Mapping File

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="Person" table="person">
        <id name="id" column="id">
            <generator class="native"/>
        </id>
        <property name="name" column="name"/>
        <property name="dob" column="dob"/>
    </class>
</hibernate-mapping>

4- Create the Hibernate SessionFactory object

Configuration cfg = new Configuration();
cfg.configure("hibernate.cfg.xml");
SessionFactory sessionFactory = cfg.buildSessionFactory();

5- Open a Hibernate session

Session session = sessionFactory.openSession();

– Saving objects-

To save a persistent object using Hibernate in a MySQL database with XML configuration and XML mapping files, you need to follow these steps:

Step1 – Create a Person object –

Create a Person object and set its properties using the setter methods.

Person person = new Person();
person.setName("Kuldeep kaushik");
person.setDob(new Date());

Step 2: Save the Person object

Save the Person object using the save() method of the Hibernate session.

Transaction transaction = session.beginTransaction();
session.save(person);
transaction.commit();

Step 3: Close the Hibernate session

Close the Hibernate session to release the database connection and free up resources.

session.close();

That’s it! Your Person object has been saved as a persistent object in the MySQL database using Hibernate with XML configuration and XML mapping files.

So complete code will look like this-

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import java.util.Date;

public class Main {
 
    public static void main(String[] args) {
 
        // Step 1: Set up the Hibernate configuration file
        Configuration cfg = new Configuration();
        cfg.configure("hibernate.cfg.xml");
 
        // Step 2: Define the Hibernate mapping file
        // Person.hbm.xml is already defined
 
        // Step 3: Create the Hibernate SessionFactory object
        SessionFactory sessionFactory = cfg.buildSessionFactory();
 
        // Step 4: Open a Hibernate session
        Session session = sessionFactory.openSession();
 
        // Step 5: Create a Person object
        Person person = new Person();
        person.setName("Kuldeep kaushik");
        person.setDob(new Date());
 
        // Step 6: Save the Person object
        Transaction transaction = session.beginTransaction();
        session.save(person);
        transaction.commit();
 
        // Step 7: Close the Hibernate session
        session.close();
 
    }
}

Similarly, for Retrieving/Updating/Deleting-

Complete code will be –

import java.util.Date;
import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;

public class Main {

    public static void main(String[] args) {

        // Step 1: Set up the Hibernate configuration file
        Configuration cfg = new Configuration();
        cfg.configure("hibernate.cfg.xml");

        // Step 2: Define the Hibernate mapping file
        // Person.hbm.xml is already defined

        // Step 3: Create the Hibernate SessionFactory object
        SessionFactory sessionFactory = cfg.buildSessionFactory();

        // Step 4: Open a Hibernate session
        Session session = sessionFactory.openSession();

        // Step 5: Create and save a new Person object
        Person person = new Person();
        person.setName("Kuldeep kaushik");
        person.setDob(new Date());

        Transaction transaction = session.beginTransaction();
        session.save(person);
        transaction.commit();

        // Step 6: Update the Person object
        transaction = session.beginTransaction();
        person.setName("Kuldeep sharma");
        session.update(person);
        transaction.commit();

        // Step 7: Retrieve the Person object
        Query<Person> query = session.createQuery("from Person where id = :id");
        query.setParameter("id", person.getId());
        List<Person> results = query.list();

        if (!results.isEmpty()) {
            Person retrievedPerson = results.get(0);
            System.out.println("Retrieved person: " + retrievedPerson.getName() + " (DOB: " + retrievedPerson.getDob() + ")");
        } else {
            System.out.println("No person found with id " + person.getId());
        }

        // Step 8: Delete the Person object
        transaction = session.beginTransaction();
        session.delete(person);
        transaction.commit();

        // Step 9: Close the Hibernate session
        session.close();
    }
}

Note – Here’s a breakdown of the changes made to the Main class:

After saving the Person object, a new transaction is started to update the Person object. The name is changed to “Kuldeep sharma” and the updated object is saved to the database.
A new query is created to retrieve the Person object using the id property. The query is parameterized to avoid SQL injection attacks.
The results of the query are retrieved and checked to see if any objects were returned. If a Person object was returned, its name and DOB are printed to the console. Otherwise, a message indicating that no Person object was found is printed.
Another transaction is started to delete the Person object from the database.
The Hibernate session is closed to free up resources.

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