Question

My project P depends on dependency A which depends on dependency B. My project’s pom.xml file includes A as a dependency, and its jar is included in P’s classpath. However, there is a NoClassDefFoundError thrown at runtime of P, which stems from missing B jars.

Shouldn’t Maven have downloaded these dependencies automatically?

Answer 1

My project P depends on dependency A [with a compile scope] which depends on dependency B [with a compile scope].

Unless B is an optional dependency of A, B should be a dependency of P with a “compile(*)” scope (see the table of Dependency Scope and read the note) and should thus be available at runtime.

However, there is a NoClassDefFoundError thrown at runtime of P, which stems from missing B jars.

Since you’re running the project under Eclipse, the class path is setup for you so I’ll exclude a mistake at this level. This leaves us with the case of the optional dependency.

PS: A very useful tool to investigate this kind of problem is dependency:tree.