Compile time and runtime dependency

Problem

There was bunch of dependency that older version of spring-boot includes as compile time dependency, meaning in your project without you explicitly including those as a dependency in your pom.xml you can use them in your code.

However, if you upgrade spring-boot version to more recent versions those dependency became RUNTIME scope, meaning those dependencies will not be included as part of the compile classpath. You must explicitly declare it as a dependency in your project in order to use it.

Why I bring this up

This is from my experience where I upgraded spring-boot to a higher version, in the older version it used a class from a transitive dependency and that compiled fine because that transitive dependency was included as a compile time dependency.

However, after upgrading it, the same transitive dependency became runtime only, thus it isn't available anymore, which lead to compilation error if you use the library without explicitly declaring it as a dependency in your pom.xml