JWT Authentication

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🗺️ JWT Authentication with Spring Boot — Full Tutorial Roadmap

🎯 Goal:

By the end, learners will understand and implement JWT-based authentication in a Spring Boot 3 / Spring Security 6 app — including login, token generation, validation, and role-based authorization.

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🧩 PHASE 1: FOUNDATIONS (Theory + Setup)

🧠 Step 1: What is JWT?

• What JWT stands for — JSON Web Token
• Structure: Header, Payload, Signature
• Example JWT and how to decode it (jwt.io)
• Stateless Authentication vs Session-based
• When to use JWT in real-world apps

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⚙️ Step 2: Spring Boot & Spring Security Basics

• How Spring Security works (filters, authentication, authorization)
• Setting up a new Spring Boot 3 project
• Disabling default login form
• Configuring your first custom SecurityFilterChain

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💡 Step 3: Project Setup

• Create a new Spring Boot project (using Spring Initializr)
• Add dependencies:
  • spring-boot-starter-security
  • spring-boot-starter-web
  • jjwt (for token)
• Folder structure: com.example.jwtsecurity ├── config ├── controller ├── filter ├── jwt ├── model ├── service └── repository

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🔐 PHASE 2: BUILDING THE AUTH SYSTEM

🧱 Step 4: Create User Entity & Repository

• Create User model with username/password/roles
• Configure UserRepository
• Use in-memory or H2 database for demo

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🧩 Step 5: Implement UserDetailsService

• Create custom UserDetailsServiceImpl
• Load user from DB
• Use PasswordEncoder (BCryptPasswordEncoder)

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🔑 Step 6: Create JwtUtil Class

• Generate JWT using username
• Set expiration time
• Validate token and extract claims

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🧱 Step 7: Create JwtAuthFilter

• Intercept every request
• Extract “Bearer token”
• Validate token
• Set authentication in SecurityContext

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⚙️ Step 8: Configure SecurityConfig

• Disable CSRF
• Permit /auth/** endpoints
• Secure /api/**
• Add JwtAuthFilter before UsernamePasswordAuthenticationFilter

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🚪 Step 9: Authentication Controller

• Create /auth/login endpoint
• Validate user credentials
• Return generated JWT token as response

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🧩 Step 10: Protected API Endpoints

• Create /api/hello or /api/user
• Add @PreAuthorize("hasRole('USER')")
• Access using token in Authorization header

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🔄 PHASE 3: ADVANCED CONCEPTS

🧭 Step 11: Refresh Tokens

• Why refresh tokens?
• Generate short-lived access + long-lived refresh token
• Endpoint: /auth/refresh

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🔐 Step 12: Role-Based Access Control

• Add roles to User entity
• Add @PreAuthorize or @Secured annotations
• Secure admin endpoints

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💣 Step 13: Handle Exceptions Properly

• Customize AuthenticationEntryPoint
• Handle invalid/expired token responses gracefully

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🧠 Step 14: Logout & Token Blacklisting (Optional)

• Stateless JWTs can’t be invalidated easily
• Discuss blacklisting (Redis / DB)
• Implement logout endpoint (optional)

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🧩 PHASE 4: REAL-WORLD PRACTICE

🚀 Step 15: Test with Postman

• Step-by-step token testing:
  1. /auth/login
  2. Copy JWT token
  3. Use in Authorization header
• Demonstrate 403 without token vs success with token

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🐳 Step 16: Dockerize the Application

• Create Dockerfile
• Run Spring Boot + MySQL containers
• Verify JWT works in containerized environment

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🧱 Step 17: Deploy to AWS (Bonus)

• Deploy using AWS Elastic Beanstalk or EC2
• Secure with HTTPS (SSL)
• Test API via public endpoint

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🧠 PHASE 5: PROJECT + WRAP UP

💻 Step 18: Mini Project — Secure REST API

Build a small app:

• UserController → /api/profile
• AdminController → /api/admin
• JWT Authentication and Role Authorization

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📚 Step 19: Summary + Best Practices

• Never store tokens in localStorage (use HttpOnly cookies)
• Use HTTPS in production
• Short token life + refresh token mechanism
• Avoid putting sensitive data in JWT payload

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🧾 Step 20: Upload Source Code to GitHub

• Clean README
• Show setup instructions
• Add Postman collection

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Read other awesome articles in Medium.com or in akcoding’s posts.

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