Decoder Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/HttpClientCodec.java lines 302–421

    private final class Decoder extends HttpResponseDecoder {
        Decoder(HttpDecoderConfig config) {
            super(config);
        }

        @Override
        protected void decode(
                ChannelHandlerContext ctx, ByteBuf buffer, List<Object> out) throws Exception {
            if (done) {
                int readable = actualReadableBytes();
                if (readable == 0) {
                    // if non is readable just return null
                    // https://github.com/netty/netty/issues/1159
                    return;
                }
                out.add(buffer.readBytes(readable));
            } else {
                int oldSize = out.size();
                super.decode(ctx, buffer, out);
                if (failOnMissingResponse) {
                    int size = out.size();
                    for (int i = oldSize; i < size; i++) {
                        decrement(out.get(i));
                    }
                }
            }
        }

        private void decrement(Object msg) {
            if (msg == null) {
                return;
            }

            // check if it's an Header and its transfer encoding is not chunked.
            if (msg instanceof LastHttpContent) {
                requestResponseCounter.decrementAndGet();
            }
        }

        @Override
        protected boolean isContentAlwaysEmpty(HttpMessage msg) {
            // Get the method of the HTTP request that corresponds to the
            // current response.
            //
            // Even if we do not use the method to compare we still need to poll it to ensure we keep
            // request / response pairs in sync.
            HttpMethod method = queue.poll();

            final HttpResponseStatus status = ((HttpResponse) msg).status();
            final HttpStatusClass statusClass = status.codeClass();
            final int statusCode = status.code();
            if (statusClass == HttpStatusClass.INFORMATIONAL) {
                // An informational response should be excluded from paired comparison.
                // Just delegate to super method which has all the needed handling.
                return super.isContentAlwaysEmpty(msg);
            }

            // If the remote peer did for example send multiple responses for one request (which is not allowed per
            // spec but may still be possible) method will be null so guard against it.
            if (method != null) {
                char firstChar = method.name().charAt(0);
                switch (firstChar) {
                    case 'H':
                        // According to 4.3, RFC2616:
                        // All responses to the HEAD request method MUST NOT include a
                        // message-body, even though the presence of entity-header fields
                        // might lead one to believe they do.
                        if (HttpMethod.HEAD.equals(method)) {
                            return true;

                            // The following code was inserted to work around the servers
                            // that behave incorrectly.  It has been commented out
                            // because it does not work with well behaving servers.
                            // Please note, even if the 'Transfer-Encoding: chunked'
                            // header exists in the HEAD response, the response should
                            // have absolutely no content.
                            //
                            //// Interesting edge case:
                            //// Some poorly implemented servers will send a zero-byte
                            //// chunk if Transfer-Encoding of the response is 'chunked'.
                            ////