Maven, Hibernate, and Spring Framework

This document provides a high-level understanding of Maven, Hibernate, and Spring, including why we use them, their core features, and how they integrate in Java applications.

Maven

What is Maven?

• Maven is a build automation and dependency management tool for Java projects.
• It simplifies project setup, building, packaging, dependency handling, and deployment.

Why Maven is Used

• Dependency Management Automatically downloads libraries (JARs) and manages versions.
• Build Automation Compiles code, runs tests, packages JAR/WAR files.
• Standard Directory Structure Makes projects predictable (src/main/java, src/test/java).
• Plugins Used for building, testing, compiling, Docker building, etc.
• Easy Integration Works with Spring, Hibernate, Jenkins, Docker, IntelliJ, Eclipse.

How Maven Works

Maven is driven by a pom.xml file that defines:

• Project metadata
• Dependencies
• Build plugins
• Build lifecycle

Example:

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

Hibernate ORM

What is Hibernate?

• Hibernate is a Java ORM (Object–Relational Mapping) framework that maps Java classes to database tables.
• It eliminates writing most SQL manually.

Why Hibernate is Used

• Less SQL coding Converts Java objects into tables/rows automatically.
• Portable (DB independent) Same Java code works with MySQL, PostgreSQL, Oracle, etc.
• HQL / Criteria API Database-independent query language.
• Caching Faster performance using first & second level cache.
• Transaction management Makes committing/rolling back easier.

Common Hibernate Annotations

• @Entity: Represents a database table
• @Id: Primary key
• @GeneratedValue: Auto-increment ID
• @OneToOne, @OneToMany, @ManyToMany: Relationships
• @Table(name="..."): Custom table name

Example Entity:

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private String name;
}

Spring Framework

What is Spring?

Spring is a lightweight, modular framework for building Java enterprise applications with:

• Dependency Injection (DI)
• Inversion of Control (IoC)
• Web MVC
• AOP
• Security
• Data access
• Cloud & Microservices (via Spring Boot)

Why Spring is Used:

• Loose Coupling Uses Dependency Injection to reduce tight coupling between classes.
• Scalable Applications Perfect for large enterprise systems.
• Spring Boot Rapid development with auto-configuration.
• Spring MVC Build REST APIs easily.
• Spring Data JPA Removes boilerplate Hibernate code.
• Highly testable DI and mocks make unit testing easy.

Core Spring Features

1. Dependency Injection / IoC: Spring creates objects and injects their dependencies automatically.

Example:

@Component
public class HelloService {
    public void sayHello() {
        System.out.println("Hello from Spring!");
    }
}

2. Spring MVC: Build REST APIs and web applications.

3. Spring Data JPA: Works on top of Hibernate to simplify database operations.

• Integration: Spring + Hibernate + Maven
• Maven manages dependencies → Spring manages beans, DI → Hibernate manages database mapping.