Securing Spring Boot Applications with JWT and Spring Security

This article demonstrates how to protect a Spring Boot web application using Spring Security and JSON Web Tokens (JWT), providing a step‑by‑step tutorial with code examples.

First, a simple Spring Boot project is created (e.g., via start.spring.io) with the spring-boot-starter-web dependency, and a basic controller returns JSON data.

A utility class JSONResult formats responses with status, message, and result fields.

The spring-boot-starter-security and jjwt dependencies are added, and a WebSecurityConfig class extends WebSecurityConfigurerAdapter to define URL access rules, disable CSRF, and register custom filters.

Custom authentication components are implemented: AccountCredentials, GrantedAuthorityImpl, CustomAuthenticationProvider, JWTLoginFilter, JWTAuthenticationFilter, and a TokenAuthenticationService that creates and validates JWTs.

Login requests are processed by JWTLoginFilter, which authenticates the user and returns a JWT in the response body; subsequent requests include the token in the Authorization: Bearer … header and are validated by JWTAuthenticationFilter.

Testing is performed with curl commands to obtain a token and access protected endpoints such as /users, demonstrating successful authentication and role‑based access control.