Expected Jsonobject but Was Jsonprimitive

I had a similar problem where server returned sometimes a JsonObject and sometimes a JsonPrimitive. When JsonPrimitive was returned I got 200 OK but it still ends up in onFailure because the types differed ( It expected a JsonObject but found a JsonPrimitive ).

public final class JsonPrimitive extends JsonElement

public final class JsonObject extends JsonElement

The com.google.gson documentation states that booth JsonPrimitive and JsonObject extend JsonElement so why not do:

JsonObject jsonObject = createJsonObject();
Call<JsonElement> requestCall = SomeInterface.sendRequest(jsonObject);
requestCall.enqueue(new Callback<JsonElement>() {
    @Override
    public void onResponse(Call<JsonElement> call, Response<JsonElement> response) {
        //Now when you get a JsonPrimitive it will still end up here because 
        //JsonPrimitive extends JsonElement
    }

    @Override
    public void onFailure(Call<JsonElement> call, Throwable t) {
    
    }
}

Jsonobject and jsonprimitive is different type each other .

JsonObject { "name":"John", "age":30, "car":null }

JsonPrimitive (string, number, boolean)

Your response model is wrong . try this .

Your API response is String and you try to get JsonObject. check your API in Postman and sure API response is JsonObject.