Spring Boot Backend Development Course, Implementing Login and Logout with JWT, Prerequisites Token-based Authentication

In this course, we will delve deeply into how to implement login and logout functionality based on JWT (JSON Web Token) using Spring Boot. This article explains the basic concepts of JWT and how to utilize JWT in Spring Boot. Furthermore, we will start with the necessary prerequisites and development environment setup, aiming to enhance understanding through actual code examples.

1. Prerequisites: Token-Based Authentication

Token-based authentication is a technology that provides a reliable authentication method between a server and a client by converting user authentication information into a token. Unlike traditional session-based authentication, this approach is advantageous for scaling as the backend server does not need to maintain the user’s state. JSON Web Token is a widely used standard in such token-based authentication.

1.1 What is JWT?

JWT is a token that contains information encoded in JSON format, primarily used for user authentication and information transmission procedures. JWT is divided into three parts:

  1. Header: Specifies the type of token and the hashing algorithm.
  2. Payload: Contains user information and additional claims (e.g., expiration time).
  3. Signature: Generated by combining the Header and Payload and hashing them with a secret key.

An example of a JWT is as follows:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

1.2 Advantages of JWT

  • Statelessness: The server does not need to maintain sessions.
  • Cross-Domain Authentication: Authentication information can be stored on the client, making it usable across various clients.
  • Security: Capable of encryption and signing on its own.

2. Environment Setup

To use Spring Boot, prepare the following items.

2.1 Development Tool Setup

  1. Install Java Development Kit (JDK) version 17 or higher.
  2. Create a project using Spring Initializr (adding web, security, JPA, and Lombok dependencies).
  3. Install an IDE (IntelliJ IDEA or Eclipse).

2.2 Project Structure

src
├── main
│   ├── java
│   │   └── com
│   │       └── example
│   │           └── jwt
│   │               ├── JwtApplication.java
│   │               ├── controller
│   │               │   └── AuthController.java
│   │               ├── dto
│   │               │   └── AuthRequest.java
│   │               ├── security
│   │               │   ├── JwtRequestFilter.java
│   │               │   └── JwtUtil.java
│   │               └── service
│   │                   └── UserService.java
│   └── resources
│       └── application.properties
└── test