Spring/JPA and other related APIs has lots of stuff to learn. It is like the modern Java EE. It will require at-least 50–60 hours to learn basic stuff and their

Spring/JPA and other related APIs has lots of stuff to learn. It is like the modern Java EE. It will require at-least 50–60 hours to learn basic stuff and their history. Learning history like how XML configuration works might be required because some codebases might be still using it. Otherwise, just learning spring boot, assuming some things happen "by magic" will take fewer hours.