Parsing single json entry to multiple objects with Gson

Question

I have a json response that looks like this:

{
    \"id\":\"001\",
    \"name\":\"Name\",
    \"param_distance\":\"10\",
    \"param_sampling\":\"2\"
}


        

Answer 1

The way to make Gson understand it is to write a custom deserializer by creating a TypeAdapter for your Test class. You can find information in Gson's User Guide. It is not exactly a manual parsing, but it is not that different, since you have to tell Gson how to deal with each JSON value...

It should be something like this:

private class TestDeserializer implements JsonDeserializer<Test> {
  public Test deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
      throws JsonParseException {

    JsonObject obj = json.getAsJsonObject();

    int id = obj.get("id").getAsInt();
    String name = obj.get("name").getAsString();

    double distance = obj.get("param_distance").getAsDouble();
    int sampling = obj.get("param_sampling").getAsInt();

    //assuming you have suitable constructors...
    Test test = new Test(id, name, new Parameters(distance, sampling));

    return test;
  }
}

Then you have to register the TypeAdapter with:

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(Test.class, new TestDeserializer());

And finally you just have to parse your JSON as usual, with:

gson.fromJson(yourJsonString, Test.class);

Gson will automatically use your custom deserializer to parse your JSON into your Test class.