In the current version of AEM Plugin, there is a known issue while exporting a plugin created project into server. This has been fixed in the latest version of Sling IDE but the same is expected to be bundled with AEM plugin in its next release. Meanwhile to fix this issue, follow the below steps.
Step 1: Download the latest Sling IDE code from https://svn.apache.org/repos/asf/sling/trunk/tooling/ide/ . Build the above package and get ‘org.apache.sling.ide.p2update-1.0.3-SNAPSHOT.zip’ file
Or you can also download the same from here org.apache.sling.ide.p2update-1.0.3-SNAPSHOT.zip
Step 2: Then open your eclipse, Click Help > Install New Software… > and click on ‘Add’
Step 3: Click on ‘Archive’ and select the zip file that is created manually and click ‘Ok’
Step 4: Select ‘Sling’ and Click ‘Next’, agree to the license terms and install
Once it’s installed successfully, restart the eclipse. Now Import and Export of AEM project into server will be successful
Click here to see how to create an AEM project from Eclipse