Understanding JWT with Spring Boot 3

Introduction

• Welcome to Amigos Code.
• Focus on JWT (JSON Web Token) using Spring Boot 3.
• Previous crash course on Spring Security had a lag in JWT section, leading to this extensive video.
• Importance of security in API design.

Community Engagement

• Encourage liking the video and subscribing to the channel.
• Join the private Facebook group and Discord for community support.

Overview of JWT Validation Mechanism

• Process Initiation:
  • Client sends HTTP request to Spring Boot backend.
  • The first executed component is the JWT authentication filter.

JWT Authentication Filter

• Filter Purpose: Validates the JWT token for each request.
• Process Steps:
  1. Check for JWT Token:
     • If missing, respond with 403 (Forbidden).
  2. Fetch User Info:
     • Call UserDetailsService to fetch user based on email (claim from JWT).
     • If user does not exist, respond with 403.
  3. Validate JWT:
     • If token is valid, update SecurityContextHolder to authenticate user.
     • If invalid (e.g., expired), respond with 403.
  4. Forward Request:
     • Once authenticated, forward request to DispatcherServlet and Controller.

Implementation Steps

1. Create Spring Boot Project:

   • Use Spring Initializr with Maven and Java 17.
   • Add dependencies: Spring Web, Spring Security, Spring Data JPA, PostgreSQL Driver, Lombok.

2. Configure Database:

   • Use tools like pgAdmin to connect and configure PostgreSQL.
   • Modify application.yml to set up data source properties.

3. User Class Creation:

   • Attributes: id, firstName, lastName, email, password.
   • Use Lombok annotations for boilerplate reduction.
   • Make the class an entity with JPA annotations.

4. Create User Repository:

   • Extend JpaRepository to communicate with the database.
   • Add method to find user by email.

5. JWT Authentication Filter Implementation:

   • Extend OncePerRequestFilter to create a JWT authentication filter.
   • Implement logic to extract JWT from headers and validate it.

6. Create JWT Service:

   • Handle JWT generation, extraction, validation, and expiration checks.
   • Use dependencies for JWT (jjwt library).

7. Security Configuration:

   • Create a SecurityConfig class to configure security filter chains.
   • Set session management to be stateless for JWT use.
   • Configure paths that require authentication.

8. Create Authentication Controller:

   • Implement endpoints for user registration and authentication.
   • Use DTO classes for request and response objects.

9. Test Application:

   • Use Postman to test registration and authentication endpoints.
   • Verify secured endpoints and JWT functionality.

Conclusion

• Understanding JWT with Spring Boot 3 enhances API security.
• Call to action: like the video, subscribe to the channel for more content.

Key Takeaways

• JWT is essential for securing APIs.
• Spring Boot simplifies JWT implementation through filters and services.
• Community support is vital for learning and troubleshooting.
• Practice by building a sample application to cement learning.