Bug 26699 Create Jar fails with no warning if jar read-only
Once *.jardesc has been created, if I invoke "Create JAR" from the context menu and the jar file already exists and is read-only, the progress dialog flashes and nothing more happens. Please add check for this condition and at least an error message should be displayed. Even better, ask something like "Jar file read-only, overwrite?" Y/N and overwrite the file on yes (similar to what the option "warn if jar file exists" does).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.ui.jarpackager.IJarDescriptionWriter;
import org.eclipse.jdt.ui.jarpackager.IJarExportRunnable;
import org.eclipse.jdt.ui.jarpackager.JarPackageData;
import org.eclipse.jdt.ui.jarpackager.JarWriter;
import org.eclipse.jdt.internal.corext.util.JavaModelUtil;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.JavaStatusConstants;
import org.eclipse.jdt.internal.ui.util.BusyIndicatorRunnableContext;
/**
 * Operation for exporting a resource and its children to a new  JAR file.
 */
public class JarFileExportOperation implements IJarExportRunnable {
	private static class MessageMultiStatus extends MultiStatus {
		MessageMultiStatus(String pluginId, int code, String message, Throwable exception) {
			super(pluginId, code, message, exception);
		}
		/*
		 * allows to change the message
		 */
		protected void setMessage(String message) {
			super.setMessage(message);
		}
	}
	private JarWriter fJarWriter;
	private JarPackageData fJarPackage;
	private JarPackageData[] fJarPackages;
	private Shell fParentShell;
	private Map fJavaNameToClassFilesMap;
	private IContainer fClassFilesMapContainer;