@Override
    public long getContentLength() {
      return outputStream.getByteCount();
    }
While sound idea in theory to "count the bytes as you stream/write", thus preserving memory,
this does not work in practice since the HTTP headers must be written to the HTTP output stream
response before the body!
geode-web-api/src/main/java/org/apache/geode/rest/internal/web/http/converter/CustomMappingJackson2HttpMessageConverter.java