WebSocketClientExtensionHandler Class — netty Architecture

Source Code

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/extensions/WebSocketClientExtensionHandler.java lines 43–127

public class WebSocketClientExtensionHandler extends ChannelDuplexHandler {

    private final List<WebSocketClientExtensionHandshaker> extensionHandshakers;

    /**
     * Constructor
     *
     * @param extensionHandshakers
     *      The extension handshaker in priority order. A handshaker could be repeated many times
     *      with fallback configuration.
     */
    public WebSocketClientExtensionHandler(WebSocketClientExtensionHandshaker... extensionHandshakers) {
        this.extensionHandshakers = Arrays.asList(checkNonEmpty(extensionHandshakers, "extensionHandshakers"));
    }

    @Override
    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
        if (msg instanceof HttpRequest && WebSocketExtensionUtil.isWebsocketUpgrade(((HttpRequest) msg).headers())) {
            HttpRequest request = (HttpRequest) msg;
            String headerValue = request.headers().getAsString(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS);
            List<WebSocketExtensionData> extraExtensions =
              new ArrayList<WebSocketExtensionData>(extensionHandshakers.size());
            for (WebSocketClientExtensionHandshaker extensionHandshaker : extensionHandshakers) {
                extraExtensions.add(extensionHandshaker.newRequestData());
            }
            String newHeaderValue = WebSocketExtensionUtil
              .computeMergeExtensionsHeaderValue(headerValue, extraExtensions);

            request.headers().set(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS, newHeaderValue);
        }

        super.write(ctx, msg, promise);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg)
            throws Exception {
        if (msg instanceof HttpResponse) {
            HttpResponse response = (HttpResponse) msg;

            if (WebSocketExtensionUtil.isWebsocketUpgrade(response.headers())) {
                String extensionsHeader = response.headers().getAsString(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS);

                if (extensionsHeader != null) {
                    List<WebSocketExtensionData> extensions =
                            WebSocketExtensionUtil.extractExtensions(extensionsHeader);
                    List<WebSocketClientExtension> validExtensions =
                            new ArrayList<WebSocketClientExtension>(extensions.size());
                    int rsv = 0;

                    for (WebSocketExtensionData extensionData : extensions) {
                        Iterator<WebSocketClientExtensionHandshaker> extensionHandshakersIterator =
                                extensionHandshakers.iterator();
                        WebSocketClientExtension validExtension = null;

                        while (validExtension == null && extensionHandshakersIterator.hasNext()) {
                            WebSocketClientExtensionHandshaker extensionHandshaker =
                                    extensionHandshakersIterator.next();
                            validExtension = extensionHandshaker.handshakeExtension(extensionData);
                        }

                        if (validExtension != null && ((validExtension.rsv() & rsv) == 0)) {
                            rsv = rsv | validExtension.rsv();
                            validExtensions.add(validExtension);
                        } else {
                            throw new CodecException(
                                    "invalid WebSocket Extension handshake for \"" + extensionsHeader + '"');
                        }
                    }

                    for (WebSocketClientExtension validExtension : validExtensions) {
                        WebSocketExtensionDecoder decoder = validExtension.newExtensionDecoder();
                        WebSocketExtensionEncoder encoder = validExtension.newExtensionEncoder();
                        ctx.pipeline().addAfter(ctx.name(), decoder.getClass().getName(), decoder);
                        ctx.pipeline().addAfter(ctx.name(), encoder.getClass().getName(), encoder);
                    }
                }

                ctx.pipeline().remove(ctx.name());
            }
        }