Eclipse java debugging: source not found

While debugging a java app in eclipse I receive a “Source not found” error in two cases:

• Stepping in to a file in a different project which is already imported
• Stepping in to a file in an installed maven repository

The files are there, but eclipse won’t step into them, instead it shows a button to “attach source“

I tried attaching (which opened a dialog to define a variable?!) and eclipse did jump to the file, but the debugger could not inspect any variables there. Also manually attaching the source for each dependency isn’t practical, as in my case there are thousands of dependency files.

I’m new to eclipse\java so an explanation of why this is happening + how to resolve this would help a lot!

Just 3 steps to configuration Eclipse IDE:

Note: After updating the Source Lookup paths, you’ll have to stop and restart your debug session. Otherwise, the file with the missing source will continue to show “missing source”.

Edit Source Lookup
Select the Edit Source Lookup… command [ Edit Source Lookup ] to open the Source Path Dialog, which allows you to make changes to the source lookup path of the selected debug target.

IMPORTANT Restart Eclipse after this last step.