Bug 31556 Export jar from Navigator view fails
(M5 build) In Navigator view (resource perspective), right-click on a src/ directory containing your sources, select export->jar file and the package selector opens with no resource selected (and finish button disabled); but it seems that the src/ dir is really selected, because if you re-select it in the window, it ends up with a "jar creation failed" and a lot of duplicate entries in the error log. If you try the same from the Projects view (Java browsing perspective), it works fine.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarPackageWizardPage.java
}
			}
		}
		
		String currentMessage= getMessage();
		if (!(new File(fDestinationNamesCombo.getText()).isAbsolute())) {
			if (currentMessage == null)
				setMessage(JarPackagerMessages.getString("JarPackageWizardPage.info.relativeExportDestination"), WizardPage.INFORMATION); 
		} else {
			if (currentMessage != null)
				setMessage(null);
		}
		return ensureTargetFileIsValid(fJarPackage.getJarLocation().toFile());
	}
	/*
	 * Overrides method from WizardDataTransferPage
	 */
	protected boolean validateOptionsGroup() {
		return true;
	}
	/*
	 * Overrides method from WizardDataTransferPage
	 */
	protected boolean validateSourceGroup() {
		if (!fExportClassFilesCheckbox.getSelection()
				&& !fExportJavaFilesCheckbox.getSelection()) {
			setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.noExportTypeChecked")); 
			return false;
		}
		if (getSelectedResources().size() == 0) {