IntermediaryHandler Class — netty Architecture

Source Code

handler-proxy/src/test/java/io/netty/handler/proxy/ProxyServer.java lines 153–261

    protected abstract class IntermediaryHandler extends SimpleChannelInboundHandler<Object> {

        private final Queue<Object> received = new ArrayDeque<Object>();

        private boolean finished;
        private Channel backend;

        @Override
        protected final void channelRead0(final ChannelHandlerContext ctx, Object msg) throws Exception {
            if (finished) {
                received.add(ReferenceCountUtil.retain(msg));
                flush();
                return;
            }

            boolean finished = handleProxyProtocol(ctx, msg);
            if (finished) {
                this.finished = true;
                ChannelFuture f = connectToDestination(ctx.channel().eventLoop(), new BackendHandler(ctx));
                f.addListener((ChannelFutureListener) future -> {
                    if (!future.isSuccess()) {
                        recordException(future.cause());
                        ctx.close();
                    } else {
                        backend = future.channel();
                        flush();
                    }
                });
            }
        }

        private void flush() {
            if (backend != null) {
                boolean wrote = false;
                for (;;) {
                    Object msg = received.poll();
                    if (msg == null) {
                        break;
                    }
                    backend.write(msg);
                    wrote = true;
                }

                if (wrote) {
                    backend.flush();
                }
            }
        }

        protected abstract boolean handleProxyProtocol(ChannelHandlerContext ctx, Object msg) throws Exception;

        protected abstract SocketAddress intermediaryDestination();

        private ChannelFuture connectToDestination(EventLoop loop, ChannelHandler handler) {
            Bootstrap b = new Bootstrap();
            b.channel(NioSocketChannel.class);
            b.group(loop);
            b.handler(handler);
            return b.connect(intermediaryDestination());
        }

        @Override
        public final void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
            ctx.flush();
        }

        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            if (backend != null) {
                backend.close();
            }
        }

        @Override
        public final void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            recordException(cause);
            ctx.close();
        }

        private final class BackendHandler extends ChannelInboundHandlerAdapter {