CODEWITHSUNDEEP
javajsongson
csvan
csvan

Reputation: 9454

Include object type when serializing using GSON

Let's say I have a some basic types:

public class Base {
    String a = "a";
    Nested nested = new Nested()
}

public class Nested {
    String b = "b",
}

Serialising this with GSON, I get:

{
   "a": "a",
   "nested": {
      "b": "b"    
   }
}

This is all good, but what if I want to preserve the object type as well, according to the following:

{
    "Base":
    {
       "a": "a",
       "nested": {
           "Nested": {
               "b": "b"  
           }  
       }
    }
}

I could try writing a custom serializer to solve this (Just assume an equivalent one is written for Nested as well):

new JsonSerializer<Base>() {
    @Override
    public JsonElement serialize(Base src, Type typeOfSrc, JsonSerializationContext context) {
         Map<String, Base> selfMap = new HashMap<>();
         selfMap.put(src.getClass().getSimpleName(), src);
         return context.serialize(selfMap);
     }
}

The problem with this, however, is of course that I get stuck in an infinite recursion when serializing the base type.

Is there any other way to solve this?

Upvotes: 3

Views: 750

Answers (3)

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35557

You can try in this way

Base base = new Base();
base.a="a";  
base.b="b";

Gson gson = new Gson();
JsonElement je = gson.toJsonTree(base);
JsonObject jo = new JsonObject();
jo.add(Base.class.getName(), je);
System.out.println(jo.toString());

Out put:

{"Base":{"a":"a","b":"b"}}

Edit:

for your edit in the question.

You can try with Genson 

Base base = new Base();
base.a="a";
base.nested=new Nested();

Genson genson = new Genson.Builder().setWithClassMetadata(true).create();
String json = genson.serialize(base);
System.out.println(json.replaceAll("\"@class\":",""));

Out put:

{"Base","a":"a","nested":{"Nested","b":"b"}}

Upvotes: 1

Ken de Guzman
Ken de Guzman

Reputation: 2810

Why not just add the class name in top of object tree. You could have something like this.

 Gson gson = new Gson();
 JsonElement je = gson.toJsonTree(new Base());
 JsonObject jo = new JsonObject();
 jo.add(Base.class.getSimpleName(), je);

Upvotes: 0

William Falcon
William Falcon

Reputation: 9813

Just subclass the gson serializer and serialize the object as normal. Once you have it, get the class name using introspection and set it as the key to a new map with the value being gson's json object. Return this object now from your custom serialize method.

Don't override the custom serialize method, jus create a new one that uses the original serialize method.

Upvotes: 0

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