How do you secure REST endpoints with JWT in Spring Boot?

Table of Contents

Introduction

JSON Web Tokens (JWT) are a popular method for securing RESTful APIs. JWT tokens are compact, URL-safe tokens that are used to securely transmit information between parties, commonly for user authentication and authorization. In Spring Boot, you can integrate JWT to secure REST endpoints, ensuring that only authorized users can access protected resources.

In this guide, we’ll walk through the steps to secure REST endpoints with JWT in a Spring Boot application. We will cover:

  • How to generate JWT tokens upon login.
  • How to create a filter to validate JWT tokens in incoming requests.
  • How to configure Spring Security to secure your endpoints using JWT.

Steps to Secure REST Endpoints with JWT

1. Add Dependencies

To start, ensure your Spring Boot application has the required dependencies for Spring Security and JWT handling. You will need to include spring-boot-starter-security for authentication and jjwt for working with JWT tokens.

Here’s the necessary dependency in your pom.xml:

2. Create JWT Utility Class

Create a utility class to handle JWT creation, parsing, and validation. This class will provide methods to generate a token, extract claims, and validate the token.

Example JwtUtil.java:

In this class:

  • createJwt() generates a JWT token.
  • parseJwt() parses the token and retrieves the claims.
  • isTokenExpired() checks if the token is expired.

3. Create JWT Filter

A filter is needed to intercept HTTP requests and validate the JWT token in the Authorization header. If the token is valid, the user is authenticated and the request proceeds. If not, an error is returned.

Example JwtFilter.java:

In this filter:

  • The JWT token is extracted from the Authorization header.
  • The token is validated for expiration and authenticity.
  • If valid, the user is authenticated by setting the SecurityContext.

4. Create Authentication Token Class

Create a custom authentication token class to hold the user’s information (like the username) extracted from the JWT. This class will be used by Spring Security to represent the user’s authentication.

Example JwtAuthenticationToken.java:

5. Configure Spring Security

Now, configure Spring Security to integrate the JWT filter. You will need to add the filter to the security filter chain to ensure that every incoming request is validated for a JWT token.

Example SecurityConfig.java:

In this configuration:

  • The /login endpoint is accessible without a token.
  • All other requests are secured, requiring a valid JWT token.
  • The JwtFilter is added to the Spring Security filter chain before other filters.

6. Create Login Endpoint to Generate JWT Token

Create an endpoint to allow users to log in and generate a JWT token. This endpoint will authenticate the user and issue a JWT token.

Example AuthController.java:

In this controller:

  • The /login endpoint generates and returns a JWT token when the user submits valid credentials.

Conclusion

Securing REST endpoints with JWT in Spring Boot involves:

  1. Generating JWT tokens upon successful authentication.
  2. Validating tokens using a custom filter to ensure that only authenticated users can access protected resources.
  3. Configuring Spring Security to enforce token-based authentication across the application.

By following these steps, you can implement JWT-based security in your Spring Boot application, ensuring that only authorized users have access to your RESTful API endpoints.

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