JWT Login in Spring Boot 4 Without jjwt or a Custom Filter

In this article, we will demonstrate how to implement JWT login in Spring Boot 4 using the built-in OAuth2 Resource Server module, without the need for additional JWT libraries or custom filters. By utilizing Spring Security, you can easily verify tokens signed with a secret key and grant access to protected endpoints based on the roles present in the token.

The article outlines a step-by-step process to set up JWT login in a Spring Boot application. First, you need to add the necessary dependencies to your project, including the Spring Boot starters for web, security, and OAuth2 resource server. These starters provide the essential components needed for handling HTTP requests, managing security configurations, and validating JWT tokens.

Next, you must generate a secret key to sign the JWT tokens. The secret key must be at least 32 bytes long and can be generated using a tool like OpenSSL. In the application.yml configuration file, you define the secret key as a property and specify the issuer of the tokens.

After setting up the secret key, you need to configure the JWT encoder and decoder. The JwtEncoder is responsible for generating new tokens, while the JwtDecoder validates incoming tokens. The decoder checks the signature, expiry time, and issuer claim of the token to ensure its validity. By using the Nimbus library, which is included in the Spring Boot OAuth2 Resource Server starter, you can easily create the encoder and decoder beans in your application's configuration class.

Once the JWT encoder and decoder are configured, you can create a TokenService to generate tokens for authenticated users. The TokenService will use the configured JwtEncoder to sign tokens and set the issuer and token lifetime (ttl) in minutes.

With the JWT infrastructure in place, you can now implement the four endpoints required for JWT login: a login endpoint to validate user credentials and issue a token, a public endpoint that can be accessed without a token, a protected endpoint that requires a valid token, and a protected endpoint that requires a token with the ADMIN role. By leveraging Spring Security's annotation-based security configuration, you can easily protect these endpoints and grant access based on the roles present in the JWT token.

In conclusion, this article provides a simple and efficient way to implement JWT login in Spring Boot 4 using the built-in OAuth2 Resource Server module. By following the steps outlined in the article and leveraging the power of Spring Security, you can easily add JWT authentication to your application without the need for additional libraries or custom filters.