Last two years I worked on Spring Boot Applications with Springfox. Springfox generate a documentation and a test ui for your REST API.
But actually Springfox project is dead and do not support the newest Spring.
How do you implement swagger ui into a Spring Boot 3.4 project?
I haven't tried it myself yet, but this looks quite promising:
https://github.com/springdoc/springdoc-openapi
OpenAPI 3.0 is the successor of Open API 2.0 (sometimes referred to as Swagger, though that is actually the tooling around Open API). Not sure how much this project offers in terms of customization and how mature it is, but I guess it's worth a try ;-)
Update:
Since version 3, Spring Fox offers support for Open API 3. Please see the release log for more details.