Starters

The file spring-boot-starter-webmvc-4.1.2.jar is 4,749 bytes long. When we listed its contents, it held a manifest, a license, and a notice file, and not a single Java class. Yet this one dependency put 34 library jars into the packaged booking service.

A starter is valuable because of the list it carries, not because of the code inside it. That list, and a second list that fixes a version for every library on it, decide most of what the service can do before you write a line