How do you implement token validation in Spring Boot?

Table of Contents

• Introduction
  • Steps to Implement Token Validation in Spring Boot
    • 1. Add Dependencies
    • 2. Create a JWT Utility Class
    • 3. Create a JWT Filter for Validation
    • 4. Create an Authentication Token Class
    • 5. Register the JWT Filter
• Conclusion

Introduction

Token-based authentication, such as using JSON Web Tokens (JWTs), is a common method for securing RESTful APIs. After generating and issuing a JWT token during the login process, it becomes crucial to validate the token on subsequent requests to ensure that users are authenticated and authorized to access protected resources.

In this guide, we will explain how to implement token validation in a Spring Boot application using JWT. We will cover how to:

• Create a filter to intercept requests and validate the token.
• Use Spring Security to manage authentication and authorization.
• Extract and validate the token from the HTTP request headers.

Steps to Implement Token Validation in Spring Boot

1. Add Dependencies

Ensure that your Spring Boot project includes the necessary dependencies for Spring Security and JWT handling. The main dependencies required are spring-boot-starter-security for security and jjwt for working with JWTs.

Example pom.xml dependencies:

2. Create a JWT Utility Class

You need a utility class that will handle the generation, parsing, and validation of JWT tokens. This class will include methods to create a JWT token, parse it, and validate its signature and expiration.

Example JwtUtil.java:

3. Create a JWT Filter for Validation

To validate the JWT token on each request, you need a filter that will intercept incoming requests and check the presence and validity of the token. This filter will extract the token from the Authorization header of the HTTP request and validate it using the JwtUtil class.

Example JwtFilter.java:

In this filter:

• The Authorization header is extracted, and the JWT token is parsed.
• The token is validated to check if it’s expired or malformed.
• If the token is valid, the user’s authentication is set in the SecurityContext.

4. Create an Authentication Token Class

For Spring Security to handle the authentication, you’ll need a custom authentication token class. This class will hold the username or any other authentication data extracted from the JWT.

Example JwtAuthenticationToken.java:

5. Register the JWT Filter

Now that we have the filter to validate the JWT token, we need to register it with Spring Security. You can do this by creating a custom security configuration class.

Example SecurityConfig.java:

In this configuration:

• The JwtFilter is added before other filters in the filter chain.
• The /login endpoint is allowed without authentication, while other endpoints require a valid JWT token.

Conclusion

Token validation in Spring Boot is essential for securing RESTful APIs. By implementing a JWT filter and integrating it with Spring Security, you can ensure that only authorized users can access protected resources. This process involves extracting the token from the Authorization header, validating it using a utility class, and setting the authentication context for further request processing. With this setup, your Spring Boot application will be able to handle token-based authentication securely and efficiently.