public ViewManagerProvider getViewManagerProvider(String extension) {
String className = extensionMap.get(extension);
if (className == null)
return getDefaultViewManagerProvider();
ViewManagerProvider vmp = viewManagerProviders.get(className);
if (vmp == null) {
try {
vmp = (ViewManagerProvider) loader.loadClass(className).newInstance();
viewManagerProviders.put(className, vmp);
} catch (Exception e) {