When developing in spring + maven environment, Java changes are automatically reflected by devtools, but static files such as HTML are not automatically reflected. If you have not changed the file structure etc., you can add the following settings to application.yml (or application.properties) so that the changes will be reflected in the browser immediately.
spring: thymeleaf: prefix: classpath:/templates/
Or it will be reflected in this way of writing.
spring: thymeleaf: prefix: file:src/main/resources/templates/