🌱 Spring Boot Learning Repository

Welcome to my Spring Boot Learning Repository!
This repo contains examples, notes, and practice projects I’ve built while learning Spring Boot and related backend frameworks.

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🧠 Language and Tools

• Language: Java
• Framework: Spring Boot
• Databases: MySQL / PostgreSQL
• Tools Used: STS4, IntelliJ IDEA, Postman, Maven

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🧱 CRUD REST API Application

📘 About

This is a simple REST API application that performs CRUD (Create, Read, Update, Delete) operations.
It demonstrates how to handle data using HTTP methods such as:

• POST → Create new data
• GET → Retrieve data
• PUT → Update existing data
• DELETE → Remove data

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🚀 What is Spring Boot?

Spring Boot is a Java-based framework designed to simplify the development of standalone, production-grade Spring applications.
It eliminates boilerplate configuration and provides built-in support for embedded servers, making it extremely easy to get started with minimal setup.

✨ Key Features of Spring Boot

• Auto Configuration: Automatically configures your project based on added dependencies.
• Embedded Servers: No need for external servers — uses Tomcat, Jetty, or Undertow.
• Production Ready: Built-in tools for health checks, metrics, and monitoring.
• Spring Initializr: Quickly create new Spring Boot projects with required dependencies.
• Dependency Management: Uses “starter” dependencies (like spring-boot-starter-web) to simplify configuration.

🧩 What’s Inside Spring Boot

Spring Boot internally includes several modules:

• Spring Core – Provides dependency injection and core container features.
• Spring MVC – Supports building RESTful APIs and web apps.
• Spring Data JPA – Handles database operations and ORM mapping.
• Spring Security – Adds authentication and authorization layers.
• Spring Boot Actuator – Offers health and performance monitoring endpoints.

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🧰 What is Postman?

Postman is a powerful API testing and collaboration tool used by developers to test, debug, and document RESTful APIs.
It helps verify that your Spring Boot backend endpoints are working correctly before connecting them to a frontend or mobile app.

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🔍 Why Developers Use Postman

• 🧪 Test REST APIs easily: You can send HTTP requests like GET, POST, PUT, DELETE and instantly see the server’s response.
• ⚙️ Check response data: View status codes, headers, and JSON responses clearly.
• 🔐 Handle authentication: Supports API keys, Bearer tokens, Basic Auth, and OAuth.
• 🧰 Environment variables: Define variables (like base URLs or tokens) for different setups — development, testing, production.
• 📦 Collections: Organize multiple API requests into folders, making it easy to manage large projects.
• 💾 Export & Share: You can share your API tests with teammates or import/export as JSON files.
• 🔄 Automated Testing: You can create scripts using JavaScript inside Postman for automation or CI/CD testing.

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🧪 Example Usage with Spring Boot

1. Run your Spring Boot app → usually runs at http://localhost:8080/
2. Open Postman → Create a new request tab
3. Choose a method (like GET, POST, PUT, or DELETE)
4. Enter your endpoint, for example:
   • GET http://localhost:8080/Earth
   • POST http://localhost:8080/Earth
5. For POST/PUT, go to the Body tab → select raw → JSON → and type:

   {
     "name": "Pirate",
     "tech": "Java",
     "aid": 101
   }
   
   

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💫 About Me

• 🌱 I love learning and building web applications
• ✨ Currently working on projects about environment & awareness
• 🎯 Interested in Java, Spring Boot, Frontend & API development
• 📚 Always exploring new technologies to grow

🗄️ What is JPA (Java Persistence API)?

JPA is a specification that allows you to manage relational data in Java applications.
It defines how Java objects (entities) are mapped to database tables.

⚙️ Why Use JPA

• Simplifies database operations (CRUD) using objects instead of SQL queries.
• Works with ORM frameworks like Hibernate for automatic SQL generation.
• Allows easy data persistence and retrieval using Repository Interfaces.

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💡 Example

public interface HumanRepo extends JpaRepository<Human, Integer> {
    List<Human> findByTech(String tech);
    List<Human> findByAidGreaterThan(int aid);
    
    @Query("from Human where tech=?1 order by name")
    List<Human> findByTechSorted(String tech);
}