Spring Cloud Gateway中请求转发的核心代码是什么？

public Mono< Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) { URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR); String scheme = requestUrl.getScheme(); if (isAlreadyRouted(exchange) || !"forward".equals(scheme)) { return chain.filter(exchange); } setAlreadyRouted(exchange); //TODO: translate url? if (log.isTraceEnabled()) { log.trace("Forwarding to URI: "+requestUrl); } return this.dispatcherHandler.handle(exchange); }