How to ask gson to avoid escaping json in a json response?

Question

I have a response object like this:

public class TestResponse {

    private final String response;
    private final ErrorCodeEnum error;
    private final StatusCodeEnum status;

    // .. constructors and getters here
}

I am serializing above class using Gson library as shown below:

Gson gson = new GsonBuilder().setPrettyPrinting().serializeNulls().create();
System.out.println(gson.toJson(testResponseOutput));

And the response I am getting back is shown below:

{
  "response": "{\"hello\":0,\"world\":\"0\"}",
  "error": "OK",
  "status": "SUCCESS"
}

As you can see, my json string in "response" field is getting escaped. Is there any way I can ask gson not to do that and instead return a full response like this:

{
  "response": {"hello":0,"world":"0"},
  "error": "OK",
  "status": "SUCCESS"
}

And also - Is there any problem if I do it above way?

NOTE: My "response" string will always be JSON string or it will be null so only these two values will be there in my "response" string. In "response" field, I can have any json string since this library is calling a rest service which can return back any json string so I am storing that in a string "response" field.

Answer 1

If your response field can be arbitrary JSON, then you need to:

1. Define it as an arbitrary JSON field (leveraging the JSON type system already built into GSON by defining it as the root of the JSON hierarchy - JsonElement)

   public class TestResponse {
       private final JsonElement response;
   }
   

2. Convert the String field to an appropriate JSON object representation. For this, you can use GSON's JsonParser class:

   final JsonParser parser = new JsonParser();
   
   String responseJson = "{\"hello\":0,\"world\":\"0\"}";
   JsonElement json = parser.parse(responseJson); // Omits error checking, what if responseJson is invalid JSON?
   System.out.println(gson.toJson(new TestResponse(json)));
   

This should print:

{
  "response": {
    "hello": 0,
    "world": "0"
  }
}

It should also work for any valid JSON:

String responseJson = "{\"arbitrary\":\"fields\",\"can-be\":{\"in\":[\"here\",\"!\"]}}";
JsonElement json = parser.parse(responseJson);
System.out.println(gson.toJson(new TestResponse(json)));

Output:

{
  "response": {
    "arbitrary": "fields",
    "can-be": {
      "in": [
        "here",
        "!"
      ]
    }
  }
}