Function ForwardResponseMessage

runtime/handler.go:156–210

ForwardResponseMessage forwards the message "resp" from gRPC server to REST client.

(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, req *http.Request, resp proto.Message, opts ...func(context.Context, http.ResponseWriter, proto.Message) error)

// ForwardResponseMessage forwards the message "resp" from gRPC server to REST client.
func ForwardResponseMessage(ctx context.Context, mux *ServeMux, marshaler Marshaler, w http.ResponseWriter, req *http.Request, resp proto.Message, opts ...func(context.Context, http.ResponseWriter, proto.Message) error) {
	md, ok := ServerMetadataFromContext(ctx)
	if ok {
		handleForwardResponseServerMetadata(w, mux, md)
	}

	// RFC 7230 https://tools.ietf.org/html/rfc7230#section-4.1.2
	// Unless the request includes a TE header field indicating "trailers"
	// is acceptable, as described in Section 4.3, a server SHOULD NOT
	// generate trailer fields that it believes are necessary for the user
	// agent to receive.
	doForwardTrailers := requestAcceptsTrailers(req)

	if ok && doForwardTrailers {
		handleForwardResponseTrailerHeader(w, mux, md)
		w.Header().Set("Transfer-Encoding", "chunked")
	}

	contentType := marshaler.ContentType(resp)
	w.Header().Set("Content-Type", contentType)

	if err := handleForwardResponseOptions(ctx, w, resp, opts); err != nil {
		HTTPError(ctx, mux, marshaler, w, req, err)
		return
	}
	respRw, err := mux.forwardResponseRewriter(ctx, resp)
	if err != nil {
		grpclog.Errorf("Rewrite error: %v", err)
		HTTPError(ctx, mux, marshaler, w, req, err)
		return
	}
	var buf []byte
	if rb, ok := respRw.(responseBody); ok {
		buf, err = marshaler.Marshal(rb.XXX_ResponseBody())
	} else {
		buf, err = marshaler.Marshal(respRw)
	}
	if err != nil {
		grpclog.Errorf("Marshal error: %v", err)
		HTTPError(ctx, mux, marshaler, w, req, err)
		return
	}

	if !doForwardTrailers && mux.writeContentLength {
		w.Header().Set("Content-Length", strconv.Itoa(len(buf)))
	}

	if _, err = w.Write(buf); err != nil && !errors.Is(err, http.ErrBodyNotAllowed) {
		grpclog.Errorf("Failed to write response: %v", err)
	}

	if ok && doForwardTrailers {
		handleForwardResponseTrailer(w, mux, md)
	}
}

func requestAcceptsTrailers(req *http.Request) bool {
	te := req.Header.Get("TE")