Wrong deserializing List<Object> with gson

Question

I debug CUSTOMER object with List<Object> inside:

This is CUSTOMER.class:

   public class CUSTOMER { 
    
 @XmlElements({
        @XmlElement(name = "ADDRESS", type = ADDRESS.class),
        @XmlElement(name = "ZIP", type = ZIP.class),
        @XmlElement(name = "CITY", type = CITY.class),
        @XmlElement(name = "COUNTRY", type = COUNTRY.class),
    })
    protected List<Object> addressAndZIPAndCITY;
    
    // other fields
    }

But when I deserialize and create json from it, it contains only:

{
"addressAndZIPAndCITY": [
      {
        "value": "some value",
        "type": "some type"
      },
      {
        "value": "some value 2",
        "type": "some type 2"
      }]
}

The ADRESS, ZIP, CITY and COUNTRY objects titles are missing. So it's bad deserialized.

I can't change List<Object> declaration. Is there option to deserialize it as json with ADRESS, ZIP, CITY etc.? Like this:

{
    "addressAndZIPAndCITY": [{
            "ADDRESS": {
                "value": "some value",
                "type": "some type"
            }
        }, {
            "ZIP": {
                "value": "some value 2",
                "type": "some type 2"
            }
        }
    ]
}

EDIT: I mean it looks like GSON doesn't know which object is there, but may be you know how to add some annotations or something else to the model to recognize it?

Answer 1

I think you either have to write a custom serializer for CUSTOMER or you create another class from which you do the serialization:

public class GsonCustomer {
    private List<Map<String, Object>> addressAndZipAndCity = new ArrayList<>();
    // other fields
    public GsonCustomer(CUSTOMER customer) {
        for (Object o: customer.getAddressAndZipAndCity()) {
            Map<String, Object> map = new HashMap<>();
            map.put(o.getClass().getSimpleName(), o);
            addressAndZipAndCity.add(map);
        }
        // copy other fields
    }
}

// so you can do: gson.toJson(new GsonCustomer(customer))

Or as mentioned:

public class CustomerAdapter implements JsonSerializer<CUSTOMER> {

    @Override
    public JsonElement serialize(CUSTOMER customer, Type type, JsonSerializationContext jsonSerializationContext) {
        // TODO
    }
}

// Gson gson = new GsonBuilder().registerTypeAdapter(CustomerAdapter.class, new CustomerAdapter()).create();