openrtb-core/src/main/java/com/google/openrtb/json/OpenRtbJsonUtils.java
public static void writeLongField(String fieldName, long data, JsonGenerator gen)
      throws IOException {
    gen.writeFieldName(fieldName);
    writeLong(data, gen);
  }
public static void writeLongField(String fieldName, long data, JsonGenerator gen)
      throws IOException {
    gen.writeFieldName(fieldName);
    writeLong(data, gen);
  }
Writes a long, using quotes only if it's too big (over 53-bit mantissa).