Gson: Serialization issue with RuntimeTypeAdapterFactory

[ultraon]

Hello, i found after serialization root object 'type' field is not injected, for inner object 'type' fields are added. Example:

public class Test {
  public class Base {
    String baseField = "base";
  }
  public class Child extends Base {
    String childField = "child";
    Base baseInChild = new Base();
  }

  public static void main(String[] args) {
        Gson mGson = new GsonBuilder()
                .setPrettyPrinting()
                .registerTypeAdapterFactory(
                        RuntimeTypeAdapterFactory.
                                of(Base.class).
                                registerSubtype(Base.class).
                                registerSubtype(Child.class)
                )
                .create();

        final String jsonStr = mGson.toJson(new Child());
        final Base child = mGson.fromJson(jsonStr, Base.class); // ERROR HERE: "Caused by: com.google.gson.JsonParseException: cannot deserialize class mypackage.Test$Base because it does not define a field named type"
  }
}

and json output after serialization:

{
  "baseInChild": {
    "type": "Base",
    "baseField": "base"
  },
  "childField": "child",
  "baseField": "base"
//in this place should be generated field 'type' with value 'Child'
}

[ultraon]

Hello, i've found bug in RuntimeTypeAdapterFactory (line185, method create(), and resolved this issue, need replace

if (type.getRawType() != baseType)

with

if (null == type || !baseType.isAssignableFrom(type.getRawType()))

Then RuntimeTypeAdapterFactory works well as expected.
Full version: RuntimeTypeAdapterFactory

[renanferrari]

@ultraon Thanks, just ran into this issue today and your answer solved it.

[calrsom]

Thank you. This solved an issue I had with serializing an subtype with a custom serializer and type field not being included. This fix should really get pulled into the codebase.

[swankjesse]

Try replacing this:

        final String jsonStr = mGson.toJson(new Child());

With this:

        final String jsonStr = mGson.toJson(new Child(), Base.class);

[ghost]

@swankjesse i guess thats where the problem is. i tried using the same it didnt work. Am about to try with the solution which @ultraon has given.

[headsvk]

@swankjesse What if you want to serialize a List? @ultraon solution works for that

[luizfp]

The solution proposed by @ultraon have worked for me as well. I agree with @calrsom, this should be added in the codebase with the proper tests.