Projet JPA - Java Persistence API Learning Project

A comprehensive educational project demonstrating progressive JPA (Java Persistence API) concepts using Hibernate, designed for students learning database persistence in Java.

Table of Contents

• Overview
• Features
• Project Structure
• Prerequisites
• Installation
• Configuration
• Usage
  • Part 1: Basic CRUD Operations
  • Part 2: Many-to-Many Relationships
  • Part 3: Embedded Objects & Collections
  • Part 4: Inheritance Strategies
  • Part 5: Native SQL Queries
  • Part 6: JPQL & Named Queries
• Database Schema
• Learning Objectives
• Technologies Used
• Authors

Overview

This project uses a municipal governance domain model (Mayors, Communes, Departments) to demonstrate various JPA concepts across 6 progressive lessons. Each part focuses on specific JPA features, building upon previous knowledge to provide a comprehensive understanding of Java persistence.

Target Audience: Computer Science students learning enterprise Java development and ORM (Object-Relational Mapping) patterns.

Features

Part 1: Basic CRUD Operations

• Create, Read, Update, Delete operations on entities
• One-to-One relationships (Maire � Commune)
• Many-to-One relationships (Commune � Departement)
• One-to-Many relationships (Departement � Communes)
• Composite primary keys with @EmbeddedId
• Entity lifecycle management

Part 2: Many-to-Many Relationships

• Join table entities with composite keys
• Bidirectional many-to-many relationships
• Managing temporal data in relationships (date ranges)

Part 3: Embedded Objects & Collections

• @Embedded objects for value types
• @ElementCollection for basic type collections
• Cascade operations with embedded objects
• Collection ordering with @OrderBy

Part 4: Inheritance Strategies

• @MappedSuperclass inheritance pattern
• Entity hierarchy and polymorphism
• Inherited field mapping

Part 5: Native SQL Queries

• Direct SQL execution via createNativeQuery()
• Aggregate functions (COUNT, SUM)
• Parameter binding in native queries
• Result set processing

Part 6: JPQL & Named Queries

• JPQL (Java Persistence Query Language) queries
• @NamedQuery annotations
• Type-safe queries with TypedQuery
• JOIN operations and aggregations
• Bulk operations (DELETE, UPDATE)
• Case-insensitive searching

Project Structure

Prerequisites

Before running this project, ensure you have:

• Java Development Kit (JDK) 17 or higher
• Apache Maven 3.6+ for dependency management
• MySQL 8.0+ database server
• IDE (IntelliJ IDEA, Eclipse, or VS Code recommended)

Installation

1. Clone the Repository

git clone <repository-url>
cd Projet-JPA

2. Set Up MySQL Database

Create the required databases and user:

-- Create databases
CREATE DATABASE bd_glid_2025;
CREATE DATABASE bd_glid_2025_partie2;
CREATE DATABASE bd_glid_2025_partie3;
CREATE DATABASE bd_glid_2025_partie4;
CREATE DATABASE bd_glid_2025_partie6;

-- Create user and grant privileges
CREATE USER 'app_glid_2025'@'localhost' IDENTIFIED BY 'app_glid_2025';
GRANT ALL PRIVILEGES ON bd_glid_2025.* TO 'app_glid_2025'@'localhost';
GRANT ALL PRIVILEGES ON bd_glid_2025_partie2.* TO 'app_glid_2025'@'localhost';
GRANT ALL PRIVILEGES ON bd_glid_2025_partie3.* TO 'app_glid_2025'@'localhost';
GRANT ALL PRIVILEGES ON bd_glid_2025_partie4.* TO 'app_glid_2025'@'localhost';
GRANT ALL PRIVILEGES ON bd_glid_2025_partie6.* TO 'app_glid_2025'@'localhost';
FLUSH PRIVILEGES;

3. Build the Project

mvn clean install

Configuration

The project uses persistence.xml located at src/main/resources/META-INF/persistence.xml to configure 5 persistence units:

Persistence Unit	Database	Schema Action
exemple1	bd_glid_2025	update
exemple2	bd_glid_2025_partie2	update
exemple3	bd_glid_2025_partie3	update
exemple4	bd_glid_2025_partie4	update
exemple6	bd_glid_2025_partie6	create-drop

Connection Settings:

• URL: jdbc:mysql://localhost:3306/<database>
• Driver: com.mysql.cj.jdbc.Driver
• Username: app_glid_2025
• Password: app_glid_2025

To modify database credentials, edit persistence.xml:

<property name="jakarta.persistence.jdbc.user" value="your_username"/>
<property name="jakarta.persistence.jdbc.password" value="your_password"/>

Usage

Part 1: Basic CRUD Operations

Run the main application to explore basic CRUD operations:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.App"

Features demonstrated:

• ecrire() - Create a new mayor with user input
• chercher() - Find mayor by ID
• modifier() - Update mayor information
• supprimer() - Delete mayor by ID
• creerCommune() - Create commune with associated mayor
• chercherCommune() - Retrieve commune and its mayor

Entity Relationships:

• Maire � Commune (One-to-One bidirectional)
• Commune � Departement (Many-to-One)
• Departement � Communes (One-to-Many)

Example Code:

// Create EntityManager
EntityManagerFactory emf = Persistence.createEntityManagerFactory("exemple1");
EntityManager em = emf.createEntityManager();

// Create a new mayor
em.getTransaction().begin();
Maire maire = new Maire("Dupont", "Jean", Civilite.M);
em.persist(maire);
em.getTransaction().commit();

// Find by ID
Maire found = em.find(Maire.class, 1L);
System.out.println(found.getNom());

Part 2: Many-to-Many Relationships

Demonstrates join table pattern with temporal data:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.AppPartie2"

Key Concepts:

• CommuneMaire join entity with composite key
• Tracking start/end dates for relationships
• Bidirectional many-to-many associations

Part 3: Embedded Objects & Collections

Run to see embedded objects and element collections:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.AppPartie3"

Features:

• demoComposition() - Embedded address objects within mayors
• demoCollections() - Element collections for email addresses

Example:

// Create mayor with embedded address
Maire maire = new Maire("Martin", "Sophie", Civilite.Mme);
Adresse adresse = new Adresse("123 Rue de la Paix", commune);
maire.setAdresse(adresse);

// Add email collection
Set<String> emails = new HashSet<>();
emails.add("sophie.martin@mairie.fr");
maire.setEmails(emails);

Part 4: Inheritance Strategies

Demonstrates @MappedSuperclass inheritance:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.AppPartie4"

Inheritance Hierarchy:

Utilisateur (@MappedSuperclass)
    �   Employe (@Entity)

Example:

Employe employe = new Employe();
employe.setNom("Durand");
employe.setSalaire(35000.0);
em.persist(employe);

Part 5: Native SQL Queries

Execute native SQL queries:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.AppPartie5"

Methods:

• afficherNombreMaires() - Count total mayors
• afficherNomsAdressesMaires() - List names and addresses
• afficherNomAdressMaire() - Find specific mayor

Example:

// Native SQL with parameter binding
String sql = "SELECT * FROM maire WHERE nom = :nom";
Query query = em.createNativeQuery(sql, Maire.class);
query.setParameter("nom", "Dupont");
List<Maire> results = query.getResultList();

Part 6: JPQL & Named Queries

Advanced querying with JPQL:

mvn exec:java -Dexec.mainClass="tn.ensit.info3.glid.projet_jpa.AppPartie6"

Features:

• afficherMaires() - Retrieve all mayors
• afficherDepartementPopulation() - Aggregate queries with JOIN
• afficherStatistiquesCommunes() - Statistics with COUNT/SUM
• supprimerMaires() - Bulk delete operations

Example JPQL:

// Type-safe JPQL query
TypedQuery<Maire> query = em.createQuery(
    "SELECT m FROM Maire m WHERE LOWER(m.nom) LIKE :pattern",
    Maire.class
);
query.setParameter("pattern", "%dupont%");
List<Maire> results = query.getResultList();

// Named query usage
TypedQuery<Commune> query = em.createNamedQuery("Commune.byName", Commune.class);
query.setParameter("nom", "Paris");
Commune commune = query.getSingleResult();

Database Schema

Part 1 Schema (bd_glid_2025)

Tables:

• maire (id, nom, prenom, civilite, commune_id)
• commune (id, nom, departement_id)
• departement (id, nom)
• classe (niveau, annee, nombreEE) - Composite key

Constraints:

• UNIQUE(nom, prenom) on maire table
• Foreign keys with cascade options

Part 3 Schema (bd_glid_2025_partie3)

Additional Fields:

• maire.adresse_adresse - Embedded address string
• maire.adresse_commune_id - Embedded commune reference
• maire_emails - Collection table for email addresses

Key Annotations Reference

Annotation	Purpose	Example Entity
@Entity	Marks a class as a JPA entity	All model classes
@Id	Defines primary key	All entities
@GeneratedValue	Auto-generates ID values	Maire, Commune
@OneToOne	One-to-one relationship	Maire � Commune
@ManyToOne	Many-to-one relationship	Commune � Departement
@OneToMany	One-to-many relationship	Departement � Communes
@Embedded	Embeds value object	Maire.adresse
@Embeddable	Marks class as embeddable	Adresse
@ElementCollection	Collection of basic types	Maire.emails
@EmbeddedId	Composite primary key	Classe
@MappedSuperclass	Inheritance base class	Utilisateur
@NamedQuery	Pre-defined query	Commune.byName
@Enumerated	Maps enum to DB	Civilite

Learning Objectives

By working through this project, you will learn:

1. JPA Fundamentals

   • Entity lifecycle (transient, managed, detached, removed)
   • Persistence context and EntityManager
   • Transaction management

2. Relationship Mapping

   • Unidirectional vs bidirectional relationships
   • Cascade types (PERSIST, REMOVE, ALL)
   • Fetch strategies (LAZY vs EAGER)
   • Join strategies and foreign keys

3. Advanced Mapping

   • Composite keys with @EmbeddedId
   • Embedded objects with @Embedded
   • Element collections
   • Inheritance strategies

4. Querying

   • JPQL (Java Persistence Query Language)
   • Native SQL queries
   • Named queries for reusability
   • Aggregate functions and joins
   • Bulk operations

5. Best Practices

   • Entity design patterns
   • Performance optimization
   • Transaction boundaries
   • Lazy loading pitfalls

Technologies Used

Technology	Version	Purpose
Java	17	Programming language
Maven	3.x	Build automation and dependency management
JPA	3.x	Java Persistence API specification
Hibernate	7.1.10.Final	JPA provider and ORM framework
MySQL	8.0+	Relational database management system
MySQL Connector/J	9.5.0	JDBC driver for MySQL
JUnit Jupiter	5.11.0	Unit testing framework

Authors

Institution: ENSIT (�cole Nationale Sup�rieure d'Informatique et des T�l�communications)

Program: Information Technology - Year 3

Course: Database Management and JPA

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Additional Resources

• JPA Specification
• Hibernate Documentation
• MySQL Documentation
• Java Records

License

This project is for educational purposes only.

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Happy Learning! If you encounter any issues, please review the configuration settings and ensure your MySQL database is properly set up.