I checked out the existing project source code from SVN to a folder in my system. Then I opened eclipse. Import Project-> Existing Maven Project.
It imported without iss
Right click the project->Configure->Convert to Faceted Form
This solution worked for me
Delete the metadata folder. Checkout again but select "Checkout as a project configured using the New Project Wizard" instead of "Checkout as a project in the workspace". Then a New Project wizard will open, type maven there and select "Checkout Maven Projects from SCM" preferably or "Maven Project". It should work. Remember this step should be performed for Maven Projects only. For normal Projects just select Java Project or whatever relevant type Eclipse project it is.
Right click the project, then click Configure -> Convert to Maven Project. If the packages still display as ordinary folders, then right click on the folder one level up (the one that is supposed to be the source folder), then click Build Path -> Use as a source folder.
You just need to change the nature of the project.
For MAC-> Right click on project->Properties->Check Project Natures->Then add or remove according if you are having maven project then add Maven, add Java
I had the same problem. I tried a lot of things that I read on internet but the only way that I found to solve my problem was exclude all of my workspace files (.metadata folder) and create another one.
After that, I imported a existing maven project and all my problems are gone.
Check and make sure you have eclipse pointing at a Java JDK directory instead of a Java JRE directory.
I had just installed eclipse and only the JRE was in the settings. I added the JDK path, changed it to the default and clicked on Maven -> Update project. Then the packages appeared in Package Explorer.
The hint that helped me figure this out is that when I tried to use the refactor to rename a class, it wouldn't do it, complaining that it wasn't a JDK.