openrtb-core/src/main/java/com/google/openrtb/json/OpenRtbJsonUtils.java
public static void writeEnum(ProtocolMessageEnum e, JsonGenerator gen) throws IOException {
    gen.writeNumber(e.getNumber());
  }
public static void writeEnum(ProtocolMessageEnum e, JsonGenerator gen) throws IOException {
    gen.writeNumber(e.getNumber());
  }
Writes a enum value as an int, using its Protobuf number.