Spring Framework Lecture Notes by Z Ready

Overview of Spring Framework

Enterprise Market & Java: Preferred for building scalable and secure large applications.
Spring Framework: Most famous Java framework, started in 2003 to simplify Java EE. It's a comprehensive ecosystem now.
Spring Boot: Makes it easy to build applications quickly, such as creating APIs in minutes.
Spring Projects: Spring is an umbrella with multiple sub-projects like Spring Boot, Spring Cloud, Spring Data, Spring Security, etc.

IoC: Principle where control is inverted to the framework to manage object creation and lifecycle.
DI: Technique to implement IoC using Constructor injection, Setter injection, and Field injection.
Spring Container: Manages the lifecycle of beans/objects.

Spring Boot: Simplifies the creation of new applications with embedded servers and auto-configuration, reducing the need for manual setup.
Spring Initializer (start.spring.io): Tool to generate Spring Boot projects with selected dependencies like Spring Web, Spring Data, etc.
Example Project Creation: Demonstrates creating a simple Spring Boot project using Spring Initializer and coding a basic API.

Annotation-Based Configuration: Using annotations like @Component, @Autowired, @Primary, and @Qualifier to manage beans and dependencies.
Bootstrapping with SpringApplication.run: Starts the container and manages beans.
Example: Creating Dev and Laptop classes and managing their dependencies.

Creating REST Controllers: Use @RestController and @RequestMapping or @GetMapping annotations to handle HTTP requests and responses.
Serving Data: Returning data directly as JSON using Spring Boot's auto-configuration for RESTful services.
Handling Dependency Injection in Controllers: Example of creating a simple Hello World and extending to handle APIs for other functionalities.

Introduction to Spring Data JPA: Integration of JPA (Java Persistence API) in Spring Boot for simplifying database interactions using Spring Data repositories.
Configuring JPA and Database: Setting up H2 in-memory database and using application properties to configure data source and JPA settings.
Creating Repositories: Defining CRUD operations by extending JpaRepository without writing implementation code.
JPQL (Java Persistence Query Language): Writing custom queries to fetch data as needed.

Client-Side: Using React to build a user interface for an e-commerce platform, integrated with Spring Boot backend through REST APIs.
Backend API: Developing APIs for product operations (CRUD), integrating images, search functionality, and managing different layers (Controller, Service, Repository).

Add Product: Handling multi-part requests to upload product images along with product details, storing image data as byte arrays in the database.
CRUD Operations: Implementing Create, Read, Update, and Delete operations for products, along with handling file uploads and dynamic data retrieval through APIs.
Search Functionality: Developing a search feature to filter products based on various attributes using JPQL and Spring Data JPA.
Handling CORS and Validation: Configuring CORS to handle cross-origin requests and adding validation to API inputs.

Error Handling: Using response entities to manage and communicate errors and successful operations between client and server.
Configuration Management: Properly using configuration files to manage application settings for different environments (development, production).
Security and Optimization: Brief discussions on securing APIs, optimizing performance, and implementing best practices in a Spring Boot application.

Recap: Provided a comprehensive overview of Spring Framework, focusing on Spring Boot and practical implementations using Spring Data JPA and Spring Web.
Final Thoughts: Encourages continuous practice and exploration of Spring’s extensive features to build robust and scalable applications.