Token-based API authentication with Spring and JWT

Token-based authentication is a widely-used method for securing RESTful APIs. In this authentication method, the client sends an authentication request to the server, which returns a token that the client can use in subsequent requests. This token acts as a proof of authentication, allowing the server to determine the identity of the client and authorize access to protected resources.

One popular implementation of token-based authentication is JSON Web Tokens (JWT). JWTs are compact, URL-safe, and can be signed and encrypted, making them well-suited for use in RESTful APIs. In this blog, we'll explore how to implement token-based API authentication with Spring and JWT.

To get started, you'll need to add the necessary dependencies to your project. For this example, we'll be using the spring-security-jwt library, which provides a convenient way to implement JWT authentication in a Spring application. Here's an example of the dependencies you'll need to add to your project's build file:

Next, you'll need to configure the Spring Security authentication manager. The authentication manager is responsible for verifying the authenticity of the JWT token in each request. Here's an example of a simple authentication manager configuration:

In this configuration, we're allowing unauthenticated access to the /api/auth/login endpoint, and requiring authentication for all other requests. The JwtTokenFilterConfigurer is a custom filter that verifies the JWT token in each request and sets the authentication principal if the token is valid.

Next, we'll create a JWT token provider class that will be responsible for generating and verifying JWT tokens. Here's an example of a simple JWT token provider: