儿童的序列化和反序列化

Question

Let's assume I have the following structure:

abstract class foo{}
class bar1 extends foo{
     int demo1 = 0;
}
class bar2 extends foo{
     int demo1 = 0;
     int demo2 = 0;
}
class bar3 extends foo{}

Usually when I need to send a Json, I use the following code

Gson gson = new Gson()
gson.toJson(bar1);

Recieving end

Gson gson = new Gson()
bar1 test = gson.fromJson(gsonString, bar1);

The issue here is that I need to send bar1/bar2/bar3 and get back the original object - Meaning I don't know what the current JSON should be parsed back into . Another layer of complexity is added due to the fact that an array of bar1/bar2/bar3 are being sent back.

Ex:

//Issue: is the second param bar1 bar2 or bar3?
//I put a questionmark where the issues occur, due to the fact 
//that I wouldn't know on the recieving side whether I'm going 
//to recieve bar1/bar2/bar3
? test = gson.fromJson(gsonString, ?);

I tried storing the type in foo, but without being able to parse it back there is no way to know the type.

Answer 1

If you store the type in Foo like this:

private String fqcn; 

The you could do first a string search on the json string when receiving, to extract the fully qualified classname. Then you can use:

Foo test = gson.fromJson(gsonString, Class.forName( foundFqcn);