netty is adding content-length=0 header in 204 response

[BrahmKauntey]

Expected behavior

A server MUST NOT send a Content-Length header field in any response
with a status code of 1xx (Informational) or 204 (No Content). A
server MUST NOT send a Content-Length header field in any 2xx
(Successful) response to a CONNECT request

Actual behavior

netty is adding content-length=0 header in 204 response

Steps to reproduce

Run a http request/response with response code 204.

Minimal yet complete reproducer code (or URL to code)

    @Override
    @RequestMapping("/**")
    public ResponseEntity<?> handleReq(RequestEntity<byte[]> reqEntity,
                    @RequestHeader HttpHeaders reqHeaders) {
            HttpHeaders responseHeaderMap = new HttpHeaders();
            responseHeaderMap.set("abc11", "xyz11");
            responseHeaderMap.set("abc12", "xyz12");
            responseHeaderMap.set("abc13", "xyz13");
            responseHeaderMap.set("abc14", "xyz14");

            return (new ResponseEntity<byte[]>(responseHeaderMap, HttpStatus.NO_CONTENT));
    }

Netty version

4.1.82

JVM version (e.g. java -version)

jdk:17.0.5

OS version (e.g. uname -a)

Linux 4.14.35-1818.3.3.el7uek.x86_64

[hyperxpro]

Is Netty doing that or Spring?

[normanmaurer]

Sorry but we need more info here. I suspect its spring that is doing this as need does not add this kind of headers automatically.