Caused by: java.lang.IllegalAccessException: Class org.json.JSONObject can not access a member of class java.util.HashMap with modifiers "private"

DTO有3个属性：

private list aList = new ArrayList();
private Map<String,Map<String,BigDecimal>> aMapOfMaps = new HashMap<String,BigDecimal>>();
private Map<String,BigDecimal> aMap = new HashMapMap<String,BigDecimal>();

在创建JSON对象时抛出错误,
obj = new JSONObject(object);

其中object是DTO对象.
不确定我在这里做错了什么或遗漏了什么.我真的很感激任何指向soln的指针.