java - Getting the following build error: "the type {---} cannot be resolved. it is indirectly referenced from required .class files"

Question

So, I have the following setup in Eclipse (Java):

1. I have a project (lets call this "project 1") which provides an interface (which is package private)
2. I have another project ("project 2") which contains a package from project 1... Classes in this package extend the package private interfaces in "project 1" and provide a nice public interface.
3. Now, I have "project 3" which references "project 2". Project 3 then uses the public object provided in project 2.

Upon calling the constructor from project 2 in project 3, I get the following:

"the type {---} cannot be resolved. it is indirectly referenced from required .class files"

If I add a reference to project 1 from project 3, all is well. Is there a way to NOT have to reference project 3 in this way though? It really doesn't make sense to reference it.

I'm using Eclipse (Helios) with the most recent JDK etc...

Answer 1

This is a "transitive dependency". You need on your classpath all classes that are required by any class you use. So you need to have the classes from project 1 in the classpath somehow - you can package them as a .jar, for example. Or you can go to Build Path > Order and Export of Project 2, and mark Project 1 as exported.

An important thing here is that the project dependencies are a mere development "goodie" - when you execute the program standalone (or deploy it to container), the Eclipse project dependencies are gone. So you must ensure your dependencies are met.