public String getString(String key){
		String str = null;
		if(json != null){
			JSONObject v = json;
			Object o = null;
			for(String k: key.split("\\.")){
				if(!v.containsKey(k)) {
					v = null;
					break;
				}
				o = v.get(k);
				if(o == null)break;
				if(o instanceof JSONObject){
					v = (JSONObject)o;
				}else{
					str = o.toString();
				}
			}
		}
		return str;
	}