The latest articles on DEV Community by Gursimar Singh (@gursimar_singh_ab968ebd52). https://dev.to/gursimar_singh_ab968ebd52 https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.us-east-2.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F4238060%2Fc8da5be4-8b89-4dc1-820a-174d3029cbff.jpg https://dev.to/gursimar_singh_ab968ebd52 en Gursimar Singh Wed, 11 Nov 2026 00:39:59 +0000 https://dev.to/gursimar_singh_ab968ebd52/securing-kotlin-and-spring-boot-apis-with-oauth2-and-jwt-a-beginner-guide-worth-reading-94 https://dev.to/gursimar_singh_ab968ebd52/securing-kotlin-and-spring-boot-apis-with-oauth2-and-jwt-a-beginner-guide-worth-reading-94 <p>If you’ve built a REST API with Spring Boot and Kotlin but never locked it down with tokens, JetBrains has a tutorial that’s a solid place to start: <a href="https://blog.jetbrains.com/kotlin/2026/07/secure-your-apis-oauth2-and-jwt-for-beginners/" rel="noopener noreferrer">Secure Your APIs: OAuth2 and JWT for Beginners.</a></p> <p>What it covers</p> <p>The tutorial starts with the basics: the difference between authentication and authorization, the four roles in OAuth2, and how a JWT is put together. It then builds a small document management API and sets it up as a resource server that verifies RS256-signed tokens using a public key.</p> <p>From there it gets more practical. It maps scopes, roles and permissions from token claims into Spring authorities, and uses @PreAuthorize with method security so access rules live in one place instead of being scattered through controller code.</p> <p>Who it’s for</p> <p>Developers who know some Spring or Kotlin but are new to OAuth2 and JWT. You’ll want IntelliJ IDEA, Java 17 and Gradle if you follow along.</p> <p>What I’m taking from it</p> <p>The section on issuer and audience validation. It’s easy to stop once you’ve confirmed a token is properly signed, but a valid token issued for a different service shouldn’t get into yours. I see this check skipped a lot in internal APIs, and it matters more now that AI agents are calling APIs with tokens on users’ behalf.</p> <p>Read the full tutorial here: <a href="https://blog.jetbrains.com/kotlin/2026/07/secure-your-apis-oauth2-and-jwt-for-beginners/" rel="noopener noreferrer">Secure Your APIs: OAuth2 and JWT for Beginners</a></p> kotlin springboot security beginners