LowercaseEnumTypeAdapterFactory

LowercaseEnumTypeAdapterFactory

public class LowercaseEnumTypeAdapterFactory implements TypeAdapterFactory {
     public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
       Class<T> rawType = (Class<T>) type.getRawType();
       if (!rawType.isEnum()) {
         return null;
       }

       final Map<String, T> lowercaseToConstant = new HashMap<String, T>();
       for (T constant : rawType.getEnumConstants()) {
         lowercaseToConstant.put(toLowercase(constant), constant);
       }

       return new TypeAdapter<T>() {
         public void write(JsonWriter out, T value) throws IOException {
           if (value == null) {
             out.nullValue();
           } else {
             out.value(toLowercase(value));
           }
         }

         public T read(JsonReader reader) throws IOException {
           if (reader.peek() == JsonToken.NULL) {
             reader.nextNull();
             return null;
           } else {
             return lowercaseToConstant.get(reader.nextString());
           }
         }
       };
     }

     private String toLowercase(Object o) {
       return o.toString().toLowerCase(Locale.US);
     }
}

Great solution which helps me. Thank you!