It contains few lines of code to boot up tomcat, add servlets, set some context parameters. I've done this with Jetty, and sure the first few handlers/servlets

It contains few lines of code to boot up tomcat, add servlets, set some context parameters. I've done this with Jetty, and sure the first few handlers/servlets are dead simple. But when it starts to grow, manually coding these things becomes unruly quickly. As the other commentor says, converting this to Spring Boot should be easy, and a good learning exercise.