HttpContentDecoder Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/HttpContentDecoder.java lines 48–296

public abstract class HttpContentDecoder extends MessageToMessageDecoder<HttpObject> {

    static final String IDENTITY = HttpHeaderValues.IDENTITY.toString();

    protected ChannelHandlerContext ctx;
    private EmbeddedChannel decoder;
    private boolean continueResponse;
    private boolean needRead = true;
    private ByteBufForwarder forwarder;

    public HttpContentDecoder() {
        super(HttpObject.class);
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, HttpObject msg, List<Object> out) throws Exception {
        needRead = true;
        if (msg instanceof HttpResponse && ((HttpResponse) msg).status().code() == 100) {

            if (!(msg instanceof LastHttpContent)) {
                continueResponse = true;
            }
            // 100-continue response must be passed through.
            needRead = false;
            ctx.fireChannelRead(ReferenceCountUtil.retain(msg));
            return;
        }

        if (continueResponse) {
            if (msg instanceof LastHttpContent) {
                continueResponse = false;
            }
            // 100-continue response must be passed through.
            needRead = false;
            ctx.fireChannelRead(ReferenceCountUtil.retain(msg));
            return;
        }

        if (msg instanceof HttpMessage) {
            cleanup();
            final HttpMessage message = (HttpMessage) msg;
            final HttpHeaders headers = message.headers();

            // Determine the content encoding.
            String contentEncoding = headers.get(HttpHeaderNames.CONTENT_ENCODING);
            if (contentEncoding != null) {
                contentEncoding = contentEncoding.trim();
            } else {
                String transferEncoding = headers.get(HttpHeaderNames.TRANSFER_ENCODING);
                if (transferEncoding != null) {
                    int idx = transferEncoding.indexOf(',');
                    if (idx != -1) {
                        contentEncoding = transferEncoding.substring(0, idx).trim();
                    } else {
                        contentEncoding = transferEncoding.trim();
                    }
                } else {
                    contentEncoding = IDENTITY;
                }
            }
            decoder = newContentDecoder(contentEncoding);

            if (decoder == null) {
                if (message instanceof HttpContent) {
                    ((HttpContent) message).retain();
                }
                needRead = false;
                ctx.fireChannelRead(message);
                return;
            }
            decoder.pipeline().addLast(forwarder);
            // Remove content-length header:
            // the correct value can be set only after all chunks are processed/decoded.
            // If buffering is not an issue, add HttpObjectAggregator down the chain, it will set the header.
            // Otherwise, rely on LastHttpContent message.
            if (headers.contains(HttpHeaderNames.CONTENT_LENGTH)) {
                headers.remove(HttpHeaderNames.CONTENT_LENGTH);
                headers.set(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
            }
            // Either it is already chunked or EOF terminated.
            // See https://github.com/netty/netty/issues/5892