代码：

    public static void main(String[] args) {
        String str = "{\"bussDatas\":[{\"fieldDesc\":\"string\",\"isSelected\":0,\"optionType\":0,\"optionValue\":\"string\",\"orderNum\":0,\"placeHolder\":\"string\"}],\"moduleName\":\"string\",\"packageId\":\"string\",\"techDatas\":{\"fieldDesc\":\"string\",\"isSelected\":0,\"optionType\":0,\"optionValue\":\"string\",\"orderNum\":0,\"placeHolder\":\"string\"}}\n";
        JSONObject jsonObject = JSONObject.parseObject(str);

        // 格式化输出JSON
        String pretty = JSON.toJSONString(jsonObject, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue, SerializerFeature.WriteDateUseDateFormat);
        System.out.println(String.format("原始JSON：\r\n%s", pretty));

        // 获取JSON第一层所有的key
        Set<String> keys = jsonObject.keySet();
        // 获取第一层每个key对应的值 的类型
        for (String key : keys) {
            System.out.println(String.format("%s(key)：%s(值类型)", key, jsonObject.get(key).getClass().getSimpleName()));
        }
    }

输出：