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
if (getErrorMessage() != null)
				setErrorMessage(null);
			return false;
		}
		if (fExportClassFilesCheckbox.getSelection() || !fExportJavaFilesCheckbox.getSelection())
			return true;
			
		
		Iterator iter= getSelectedResourcesIterator();
		while (iter.hasNext()) {
			if (!(iter.next() instanceof IClassFile))
				return true;
		}
		if (getErrorMessage() != null)
			setErrorMessage(null);
		return false;
	}
	/*
	 * Overwrides method from WizardExportPage
	 */
	protected IPath getResourcePath() {
		return getPathFromText(fSourceNameField);
	}
	/**
	 * Creates a file resource handle for the file with the given workspace path.
	 * This method does not create the file resource; this is the responsibility
	 * of <code>createFile</code>.
	 *
	 * @param filePath the path of the file resource to create a handle for
	 * @return the new file resource handle