dhrm dhrm - 1 year ago 131
Java Question

Gson: How to change output of Enum

I've this enum:

enum RequestStatus {
OK(200), NOT_FOUND(400);

private final int code;

RequestStatus(int code) {
this.code = code;

public int getCode() {
return this.code;

and in my Request-class, I have this field:
private RequestStatus status

When using Gson to convert the Java object to JSON the result is like:

"status": "OK"

How can I change my GsonBuilder or my Enum object to give me an output like:

"status": {
"value" : "OK",
"code" : 200

Answer Source

You can use something like this:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapterFactory(new MyEnumAdapterFactory());

or more simply (as Jesse Wilson indicated):

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(RequestStatus.class, new MyEnumTypeAdapter());


public class MyEnumAdapterFactory implements TypeAdapterFactory {

    public <T> TypeAdapter<T> create(final Gson gson, final TypeToken<T> type) {
            Class<? super T> rawType = type.getRawType();
            if (rawType == RequestStatus.class) {
                return new MyEnumTypeAdapter<T>();
            return null;

    public class MyEnumTypeAdapter<T> extends TypeAdapter<T> {

         public void write(JsonWriter out, T value) throws IOException {
              if (value == null) {
              RequestStatus status = (RequestStatus) value;
              // Here write what you want to the JsonWriter. 

         public T read(JsonReader in) throws IOException {
              // Properly deserialize the input (if you use deserialization)
              return null;

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