如何使用GSON将地图映射转换为JSON，然后又转换为JSON？

Question

I've got a Map<Integer, Map<Class<?>, Serializable>> that I'm trying to store as a JSON string. Then, later, I'm trying to read from that same JSON formatted String to recreate the object. How would you do this using GSON?

Answer 1

Rather then using Map of Map try to use class structure.

Or you can use following library to achieve the same.

com.google.gson.Gson.Gson()

use following method :

public static String getJSONString(Object jsonObject)
{
    if(jsonObject == null) return "";
    return new Gson().toJson(jsonObject);
}

Answer 2

You will not have any issue at all when trying to serialize Map<Integer, Map<Class<?>, Serializable>> , the problem is when trying to deserialize the JSON back. I guess you can write your own deserializer for the Class<?> depending on what you actually need, but deserializing Serializable is not possible.

Serializable is not a concrete class, it is an interface. You can't instantiate a Serializable , you can only instantiate a concrete class that implements Serializable . Sure you can write you own custom serializer/deserializer for Serializable by including the concrete class information inside the serialized JSON, but then you need to include all possible classes which implements Serializable , which is not realistic at all.

Reference: https://sites.google.com/site/gson/gson-user-guide#TOC-Serializing-and-Deserializing-Collection-with-Objects-of-Arbitrary-Types