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Introduction

Overview

Spring Framework is a powerful framework for building enterprise-grade Java applications, supporting dependency injection, aspect-oriented programming, and more.

Key Features
  • Lightweight: Minimal overhead, easy integration.
  • Modular: Flexible architecture for selective component use.
  • Open Source: Free under the Apache License 2.0.
  • Enterprise Ready: Robust features for large-scale applications.
  • Testable: Built-in support for testing.
  • IoC Container: Manages object creation and configuration.
  • AOP: Modularizes cross-cutting concerns.
  • Microservices Ready: Supports microservices with Spring Boot.
Spring Framework Principles
  • Choice at Every Level: Offers flexibility in architectural decisions.
  • Support for Diversity: Accommodates various application architectures.
  • Strong Backward Compatibility: Ensures smooth upgrades across versions.
  • Careful API Design: Provides intuitive and consistent APIs.
  • High Code Quality: Maintains a clean structure with no circular dependencies.

Getting Started

  1. Install Prerequisites:

    • Java Development Kit (JDK)
    • Maven or Gradle

  2. Set Up a Project:

  3. Learn and Explore:

    • Refer to official documentation and guides.

Core Concepts

IoC (Inversion of Control)

  • Principle: Transfers control of object creation and dependency management to a framework.
  • Purpose: Decouples tasks from implementation, improving modularity and testability.
  • Example: Spring manages object creation and lifecycle.

IoC Container

  • Definition: A framework component implementing IoC, managing object (bean) lifecycles and dependencies.
  • Responsibilities:
    • Instantiate and configure beans.
    • Manage bean lifecycles.
  • Examples:
    • BeanFactory: Basic IoC container providing simple functionality.
    • ApplicationContext: Advanced container with additional features like AOP, event propagation and internationalization.

DI (Dependency Injection)

  • Definition: A design pattern to achieve IoC by injecting dependencies into objects.
  • Types:
    1. Constructor Injection: Dependencies via constructor.
    2. Setter Injection: Dependencies via setter methods.
    3. Field Injection: Direct injection using @Autowired (less recommended).
  • Purpose: Reduces tight coupling, improving testability and maintainability.

Relationship Between IoC, IoC Container, and DI

  • IoC is the overarching principle.
  • The IoC Container is the implementation of IoC in Spring.
  • DI is the design pattern used by the IoC Container to achieve IoC.

Resources