src/main/java/com/googlecode/objectify/util/GenericUtils.java
public static Type getMapKeyType(Type mapType) {
		Type componentType = GenericTypeReflector.getTypeParameter(mapType, Map.class.getTypeParameters()[0]);
		if (componentType == null)	// if it was a raw type, just assume Object
			return Object.class;
		else
			return componentType;
	}
public static Type getMapKeyType(Type mapType) {
		Type componentType = GenericTypeReflector.getTypeParameter(mapType, Map.class.getTypeParameters()[0]);
		if (componentType == null)	// if it was a raw type, just assume Object
			return Object.class;
		else
			return componentType;
	}
Get the key type of a Map.