The latest articles on DEV Community by Ajeet Verma (@ajeetverma01). https://dev.to/ajeetverma01 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%2F4043170%2Fd62f91ba-42f8-4901-83ca-73f8a67fcde6.jpg https://dev.to/ajeetverma01 en Ajeet Verma Thu, 23 Jul 2026 07:31:24 +0000 https://dev.to/ajeetverma01/how-i-built-jwt-authentication-in-spring-boot-beginner-friendly-guide-3hd https://dev.to/ajeetverma01/how-i-built-jwt-authentication-in-spring-boot-beginner-friendly-guide-3hd <p><strong>How I Built JWT Authentication in Spring Boot (Beginner-Friendly Guide)</strong></p> <p>Authentication is one of the first things every backend developer learns when building real-world applications.</p> <p>While learning Spring Boot, I wanted to understand how secure authentication actually works, instead of simply copying code from tutorials. So I built a complete JWT Authentication system from scratch.</p> <p>In this article, I'll share what I learned and how the authentication flow works.</p> <p><strong>Why JWT?</strong></p> <p>JWT (JSON Web Token) is a compact, secure way to authenticate users without storing session data on the server.</p> <p>This makes applications stateless, scalable, and suitable for REST APIs.</p> <p><strong>Authentication Flow</strong></p> <ol> <li><p>User signs up with an email and password.</p></li> <li><p>Password is securely hashed using BCrypt.</p></li> <li><p>User logs in with valid credentials.</p></li> <li><p>Spring Security authenticates the user.</p></li> <li><p>The server generates a JWT.</p></li> <li><p>The frontend stores the token.</p></li> <li><p>Every protected request includes the token in the Authorization header.</p></li> <li><p>A custom JWT filter validates the token before granting access.</p></li> </ol> <p><strong>What I Implemented</strong></p> <ul> <li>User Registration</li> <li>Secure Login</li> <li>Password Hashing using BCrypt</li> <li>JWT Access Token Generation</li> <li>Spring Security Configuration</li> <li>Custom JWT Authentication Filter</li> <li>Protected REST APIs</li> <li>Token Validation</li> <li>Exception Handling</li> </ul> <p><strong>Challenges I Faced</strong></p> <p>Like every beginner, I faced several issues:</p> <ul> <li>Understanding the Spring Security filter chain</li> <li>Fixing CORS errors</li> <li>Handling invalid and expired tokens</li> <li>Protecting APIs correctly</li> <li>Learning the difference between Authentication and Authorization</li> </ul> <p>Each issue helped me understand Spring Security much better.</p> <p><strong>What I Learned</strong></p> <p>Building authentication from scratch taught me much more than following tutorials.</p> <p>I now have a better understanding of:</p> <ul> <li>Spring Security</li> <li>Stateless Authentication</li> <li>JWT</li> <li>BCrypt Password Encoding</li> <li>REST API Security</li> <li>Clean Backend Architecture</li> </ul> <p><strong>What's Next?</strong></p> <p>I'm currently building more backend projects using Spring Boot and exploring Spring AI to deepen my understanding of modern Java development.</p> <p>If you have suggestions or feedback, I'd love to hear them.</p> <p>Happy Coding! 🚀</p> java springboot springsecurity jwt