In continuation to previous article on two different ways of implementing Spring Security, here in this article we will learn the third way 'How to implement Spring Boot Thymeleaf Security Login Example using UserDetailsService?'. After going through the previous article, I hope we all are very familiar with basics of Security and even the basics of Security in a Spring Boot application. This time we will create a user registration form and save users with their roles into database. Then, based on the user role, we will check the authentication and authorization functionalities with the help of predefined UserDetailsService. If you are looking for 'How to implement Security in Spring Boot using UserDetailsService with Spring Boot 3 onward?, kindly visit a