How to fix error "Updating Maven Project". Unsupported IClasspathEntry kind=4?

This issue has been fixed in m2e 1.5.0 which is available for Eclipse Kepler (4.3) and Luna (4.4)

Please see https://bugs.eclipse.org/bugs/show_bug.cgi?id=374332#c14

The problem is caused by the fact that STS (the Spring IDE/Eclipse), as well Eclipse and other Eclipse based IDE's, use the m2e(clipse) plugin but that eclipse:eclipse has been probably been run on the project. When m2e encounters a "var" .classpath entry, it throws this error.

The update sites are specified at the following url:
http://eclipse.org/m2e/m2e-downloads.html

If you can't use m2e 1.5.0 for any reason, then :

1. Disable the maven nature for the project (via the right-click menu)

2. Run mvn eclipse:clean (while your project is open in STS/eclipse). Depending on the timing, you might need to do a refresh or two on the project before re-enabling the maven nature. You should be able to see that your project has lost it's Maven nature. (The eclipse:clean goal just deletes the .project, .classpath and .settings/ files/directories. You can also just remove those files (again while the project is open) instead of running mvn eclipse:clean.)

3. Re-enable the maven nature.
   (Most of the time, this can be done by right-clicking on the project in question in the package explorer pane, and then choosing 'Configure'-> 'Convert to Maven Project')

1. Right-click on your project, select Maven -> Remove Maven Nature.

2. Open you terminal, go to your project folder and do mvn eclipse:clean

3. Right click on your Project and select “Configure -> Convert into Maven Project”

Now you got “Unsupported IClasspathEntry kind=4 Eclipse Scala” disappear.