@Override
    public long getSize(
            Object t,
            Class<?> type,
            Type genericType,
            Annotation[] annotations,
            MediaType mediaType) {
        return -1;
    }
Method that JAX-RS container calls to try to figure out serialized length
of given value. always return -1 to denote "not known".
fastjson1-compatible/src/main/java/com/alibaba/fastjson/support/jaxrs/FastJsonProvider.java