Hibernate Getting Started

pom.xml - Hibernate Dependencies

<dependencies>
    <!-- Hibernate Core -->
    <dependency>
        <groupId>org.hibernate.orm</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>6.4.0.Final</version>
    </dependency>

    <!-- MySQL Connector -->
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.2.0</version>
    </dependency>

    <!-- C3P0 Connection Pool (optional) -->
    <dependency>
        <groupId>org.hibernate.orm</groupId>
        <artifactId>hibernate-c3p0</artifactId>
        <version>6.4.0.Final</version>
    </dependency>
</dependencies>

hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <!-- Database connection -->
        <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/mydb?useSSL=false</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">password</property>

        <!-- SQL Dialect -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Show generated SQL -->
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.format_sql">true</property>

        <!-- Schema management: validate | update | create | create-drop -->
        <property name="hibernate.hbm2ddl.auto">update</property>

        <!-- Annotated entity classes -->
        <mapping class="com.example.entity.User"/>
        <mapping class="com.example.entity.Product"/>
        <mapping class="com.example.entity.Order"/>
    </session-factory>
</hibernate-configuration>

Entity Class and SessionFactory Setup

package com.example.entity;

import jakarta.persistence.*;

@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "username", nullable = false, unique = true, length = 50)
    private String username;

    @Column(nullable = false)
    private String email;

    // No-arg constructor required by Hibernate
    public User() {}

    public User(String username, String email) {
        this.username = username;
        this.email    = email;
    }

    // Getters and setters
    public Long getId() { return id; }
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }

    @Override
    public String toString() {
        return "User{id=" + id + ", username='" + username + "', email='" + email + "'}";
    }
}

package com.example.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static final SessionFactory sessionFactory;

    static {
        try {
            // Load hibernate.cfg.xml from classpath
            sessionFactory = new Configuration()
                    .configure("hibernate.cfg.xml")
                    .buildSessionFactory();
        } catch (Exception e) {
            System.err.println("SessionFactory creation failed: " + e);
            throw new ExceptionInInitializerError(e);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    public static void shutdown() {
        getSessionFactory().close();
    }
}

package com.example;

import com.example.entity.User;
import com.example.util.HibernateUtil;
import org.hibernate.*;

public class Main {
    public static void main(String[] args) {
        // Save a user
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction tx = session.beginTransaction();

        User user = new User("alice", "alice@example.com");
        session.persist(user); // INSERT INTO users ...

        tx.commit();
        session.close();
        System.out.println("Saved: " + user);

        // Retrieve the user
        session = HibernateUtil.getSessionFactory().openSession();
        User found = session.get(User.class, user.getId());
        System.out.println("Found: " + found);
        session.close();

        HibernateUtil.shutdown();
    }
}

Maven Dependencies

hibernate.cfg.xml Configuration

First Entity and SessionFactory

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