code: @Override
  	public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
  		if (isResolvable(base)) {
  			final Enumeration<String> keys = ((ResourceBundle) base).getKeys();
  			return new Iterator<FeatureDescriptor>() {
  				public boolean hasNext() {
  					return keys.hasMoreElements();
  				}
  				public FeatureDescriptor next() {
  					FeatureDescriptor feature = new FeatureDescriptor();
  					feature.setDisplayName(keys.nextElement());
  					feature.setName(feature.getDisplayName());
  					feature.setShortDescription("");
  					feature.setExpert(true);
  					feature.setHidden(false);
  					feature.setPreferred(true);
  					feature.setValue(TYPE, String.class);
  					feature.setValue(RESOLVABLE_AT_DESIGN_TIME, true);
  					return feature;
  				}
  				public void remove() {
  					throw new UnsupportedOperationException("Cannot remove");
  					
  				}
  			};
  		}
  		return null;
  	}
docs: If the base object is a ResourceBundle, returns an Iterator containing the set of keys
  available in the ResourceBundle. Otherwise, returns null. The Iterator returned must contain
  zero or more instances of java.beans.FeatureDescriptor. Each info object contains information
  about a key in the ResourceBundle, and is initialized as follows:
  <ul>
  <li>displayName - The String key name</li>
  <li>name - Same as displayName property</li>
  <li>shortDescription - Empty string</li>
  <li>expert - false</li>
  <li>hidden - false</li>
  <li>preferred - true</li>
  </ul>
  In addition, the following named attributes must be set in the returned FeatureDescriptors:
  <ul>
  <li>{@link ELResolver#TYPE} - String.class.</li>
  <li>{@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true</li>
  </ul>
  
  @param context
  The context of this evaluation.
  @param base
  The bundle to analyze. Only bases of type ResourceBundle are handled by this
  resolver.
  @return An Iterator containing zero or more (possibly infinitely more) FeatureDescriptor
  objects, each representing a key in this bundle, or null if the base object is not a
  ResourceBundle.