Chunked encoding and content-length header

1. No:

"Messages MUST NOT include both a Content-Length header field and a non-identity transfer-coding. If the message does include a non-identity transfer-coding, the Content-Length MUST be ignored." (RFC 2616, Section 4.4)

2. And no, you can use Content-Length and stream; the protocol doesn't constrain how your implementation works.

Well, you can always send a header stating the size of the file. Something like response.addHeader("File-Size","size of the file");
And ignore the Content-Length header.

The client implementation has to be tweaked to read this value, but hey you can achieve both the things you want :)