SpringCloud gateway自定义请求的 httpClient

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　　引用 的 spring cloud gateway 的版本为 2.2.5 ；

　　SpringCloud gateway 在实现服务路由并请求的具体过程是在 org.springframework.cloud.gateway.filter.NettyRoutingFilter 的过滤器中，该过滤器封装了具体的请求参数，以及根据路由规则请求的对应服务，然后根据 HttpClient 进行微服务之间的请求； 该 httpClient 类是 用netty 封装的 客户端，其包路径为 ： reactor.netty.http.client.HttpClient ;

　　查看 NettyRoutingFilter 中的 filter 实现过程：

    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        URI requestUrl = (URI)exchange.getRequiredAttribute(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR);
        String scheme = requestUrl.getScheme();
        if (!ServerWebExchangeUtils.isAlreadyRouted(exchange) && ("http".equals(scheme) || "https".equals(scheme))) {
            ServerWebExchangeUtils.setAlreadyRouted(exchange);
            ServerHttpRequest request = exchange.getRequest();
            HttpMethod method = HttpMethod.valueOf(request.getMethodValue());
            String url = requestUrl.toASCIIString();
            HttpHeaders filtered = HttpHeadersFilter.filterRequest(this.getHeadersFilters(), exchange);
            DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
            filtered.forEach(httpHeaders::set);
            boolean preserveHost = (Boolean)exchange.getAttributeOrDefault(ServerWebExchangeUtils.PRESERVE_HOST_HEADER_ATTRIBUTE, false);
            Route route = (Route)exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR);
            Flux<HttpClientResponse> responseFlux = ((RequestSender)this.getHttpClient(route, exchange).headers((headers) -> {
                headers.add(httpHeaders);
                headers.remove("Host");
                if (preserveHost) {
                    String host = request.getHeaders().getFirst("Host");
                    headers.add("Host", host);
                }

            }).request(method).uri(url)).send((req, nettyOutbound) -> {
                if (log.isTraceEnabled()) {
                    nettyOutbound.withConnection((connection) -> {
                        log.trace("outbound route: " + connection.channel().id().asShortText() + ", inbound: " + exchange.getLogPrefix());
                    });
                }

                return nettyOutbound.send(request.getBody().map(this::getByteBuf));
            }).responseConnection((res, connection) -> {
                exchange.getAttributes().put(ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR, res);
                exchange.getAttributes().put(ServerWebExchangeUtils.CLIENT_RESPONSE_CONN_ATTR, connection);
                ServerHttpResponse response = exchange.getResponse();
                HttpHeaders headers = new HttpHeaders();
                res.responseHeaders().forEach((entry) -> {
                    headers.add((String)entry.getKey(), (String)entry.getValue());
                });
                String contentTypeValue = headers.getFirst("Content-Type");
                if (StringUtils.hasLength(contentTypeValue)) {
                    exchange.getAttributes().put("original_response_content_type", contentTypeValue);
                }

                this.setResponseStatus(res, response);
                HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(this.getHeadersFilters(), headers, exchange, Type.RESPONSE);
                if (!filteredResponseHeaders.containsKey("Transfer-Encoding") && filteredResponseHeaders.containsKey("Content-Length")) {
                    response.getHeaders().remove("Transfer-Encoding");
                }

                exchange.getAttributes().put(ServerWebExchangeUtils.CLIENT_RESPONSE_HEADER_NAMES, filteredResponseHeaders.keySet());
                response.getHeaders().putAll(filteredResponseHeaders);
                return Mono.just(res);
            });
            Duration responseTimeout = this.getResponseTimeout(route);
            if (responseTimeout != null) {
                responseFlux = responseFlux.timeout(responseTimeout, Mono.error(new TimeoutException("Response took longer than timeout: " + responseTimeout))).onErrorMap(TimeoutException.class, (th) -> {
                    return new ResponseStatusException(HttpStatus.GATEWAY_TIMEOUT, th.getMessage(), th);
                });
            }

            return responseFlux.then(chain.filter(exchange));
        } else {
            return chain.filter(exchange);
        }
    }

　　

　　该方法中 有一个 getHttpClient 方法获取 httpClient 客户端实例的过程，由于在  GatewayAutoConfiguration 中 定义了 springCloud gateway 使用的 httpclient 实例，其声明并自动加载的代码如下：

@Configuration(
        proxyBeanMethods = false
    )
    @ConditionalOnClass({HttpClient.class})
    protected static class NettyConfiguration {
        protected final Log logger = LogFactory.getLog(this.getClass());

        protected NettyConfiguration() {
        }

        @Bean
        @ConditionalOnProperty(
            name = {"spring.cloud.gateway.httpserver.wiretap"}
        )
        public NettyWebServerFactoryCustomizer nettyServerWiretapCustomizer(Environment environment, ServerProperties serverProperties) {
            return new NettyWebServerFactoryCustomizer(environment, serverProperties) {
                public void customize(NettyReactiveWebServerFactory factory) {
                    factory.addServerCustomizers(new NettyServerCustomizer[]{(httpServer) -> {
                        return httpServer.wiretap(true);
                    }});
                    super.customize(factory);
                }
            };
        }

        @Bean
        @ConditionalOnMissingBean
        public HttpClient gatewayHttpClient(HttpClientProperties properties, List<HttpClientCustomizer> customizers) {
            Pool pool = properties.getPool();
            ConnectionProvider connectionProvider;
            if (pool.getType() == PoolType.DISABLED) {
                connectionProvider = ConnectionProvider.newConnection();
            } else if (pool.getType() == PoolType.FIXED) {
                connectionProvider = ConnectionProvider.fixed(pool.getName(), pool.getMaxConnections(), pool.getAcquireTimeout(), pool.getMaxIdleTime(), pool.getMaxLifeTime());
            } else {
                connectionProvider = ConnectionProvider.elastic(pool.getName(), pool.getMaxIdleTime(), pool.getMaxLifeTime());
            }

            HttpClient httpClient = HttpClient.create(connectionProvider).httpResponseDecoder((spec) -> {
                if (properties.getMaxHeaderSize() != null) {
                    spec.maxHeaderSize((int)properties.getMaxHeaderSize().toBytes());
                }

                if (properties.getMaxInitialLineLength() != null) {
                    spec.maxInitialLineLength((int)properties.getMaxInitialLineLength().toBytes());
                }

                return spec;
            }).tcpConfiguration((tcpClient) -> {
                if (properties.getConnectTimeout() != null) {
                    tcpClient = tcpClient.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, properties.getConnectTimeout());
                }

                Proxy proxy = properties.getProxy();
                if (StringUtils.hasText(proxy.getHost())) {
                    tcpClient = tcpClient.proxy((proxySpec) -> {
                        Builder builder = proxySpec.type(reactor.netty.tcp.ProxyProvider.Proxy.HTTP).host(proxy.getHost());
                        PropertyMapper map = PropertyMapper.get();
                        proxy.getClass();
                        map.from(proxy::getPort).whenNonNull().to(builder::port);
                        proxy.getClass();
                        map.from(proxy::getUsername).whenHasText().to(builder::username);
                        proxy.getClass();
                        map.from(proxy::getPassword).whenHasText().to((password) -> {
                            builder.password((s) -> {
                                return password;
                            });
                        });
                        proxy.getClass();
                        map.from(proxy::getNonProxyHostsPattern).whenHasText().to(builder::nonProxyHosts);
                    });
                }

                return tcpClient;
            });
            Ssl ssl = properties.getSsl();
            if (ssl.getKeyStore() != null && ssl.getKeyStore().length() > 0 || ssl.getTrustedX509CertificatesForTrustManager().length > 0 || ssl.isUseInsecureTrustManager()) {
                httpClient = httpClient.secure((sslContextSpec) -> {
                    SslContextBuilder sslContextBuilder = SslContextBuilder.forClient();
                    X509Certificate[] trustedX509Certificates = ssl.getTrustedX509CertificatesForTrustManager();
                    if (trustedX509Certificates.length > 0) {
                        sslContextBuilder = sslContextBuilder.trustManager(trustedX509Certificates);
                    } else if (ssl.isUseInsecureTrustManager()) {
                        sslContextBuilder = sslContextBuilder.trustManager(InsecureTrustManagerFactory.INSTANCE);
                    }

                    try {
                        sslContextBuilder = sslContextBuilder.keyManager(ssl.getKeyManagerFactory());
                    } catch (Exception var6) {
                        this.logger.error(var6);
                    }

                    sslContextSpec.sslContext(sslContextBuilder).defaultConfiguration(ssl.getDefaultConfigurationType()).handshakeTimeout(ssl.getHandshakeTimeout()).closeNotifyFlushTimeout(ssl.getCloseNotifyFlushTimeout()).closeNotifyReadTimeout(ssl.getCloseNotifyReadTimeout());
                });
            }

            if (properties.isWiretap()) {
                httpClient = httpClient.wiretap(true);
            }

            if (!CollectionUtils.isEmpty(customizers)) {
                customizers.sort(AnnotationAwareOrderComparator.INSTANCE);

                HttpClientCustomizer customizer;
                for(Iterator var7 = customizers.iterator(); var7.hasNext(); httpClient = customizer.customize(httpClient)) {
                    customizer = (HttpClientCustomizer)var7.next();
                }
            }

            return httpClient;
        }

        @Bean
        public HttpClientProperties httpClientProperties() {
            return new HttpClientProperties();
        }

        @Bean
        public NettyRoutingFilter routingFilter(HttpClient httpClient, ObjectProvider<List<HttpHeadersFilter>> headersFilters, HttpClientProperties properties) {
            return new NettyRoutingFilter(httpClient, headersFilters, properties);
        }

        @Bean
        public NettyWriteResponseFilter nettyWriteResponseFilter(GatewayProperties properties) {
            return new NettyWriteResponseFilter(properties.getStreamingMediaTypes());
        }

        @Bean
        public ReactorNettyWebSocketClient reactorNettyWebSocketClient(HttpClientProperties properties, HttpClient httpClient) {
            ReactorNettyWebSocketClient webSocketClient = new ReactorNettyWebSocketClient(httpClient);
            if (properties.getWebsocket().getMaxFramePayloadLength() != null) {
                webSocketClient.setMaxFramePayloadLength(properties.getWebsocket().getMaxFramePayloadLength());
            }

            webSocketClient.setHandlePing(properties.getWebsocket().isProxyPing());
            return webSocketClient;
        }

        @Bean
        public ReactorNettyRequestUpgradeStrategy reactorNettyRequestUpgradeStrategy(HttpClientProperties httpClientProperties) {
            ReactorNettyRequestUpgradeStrategy requestUpgradeStrategy = new ReactorNettyRequestUpgradeStrategy();
            Websocket websocket = httpClientProperties.getWebsocket();
            PropertyMapper map = PropertyMapper.get();
            websocket.getClass();
            map.from(websocket::getMaxFramePayloadLength).whenNonNull().to(requestUpgradeStrategy::setMaxFramePayloadLength);
            websocket.getClass();
            map.from(websocket::isProxyPing).to(requestUpgradeStrategy::setHandlePing);
            return requestUpgradeStrategy;
        }
    }

　　上面 代码中的 gatewayHttpClient 为 spring cloud gateway 使用的 HttpClient 实例，在spring cloud gateway 进行服务请求时，会自动配置使用该 实例。

　　如果需要自定义的 HttpClient 实例，如在 httpClient 中自定义 ip 白名单校验，https 请求证书预置，或是添加特殊认证请求头等，这种场景下需要在代码中显示的定义 gatewayHttpClient 实例，代码如下：

    @Configuration
    public class GatewayAutoConfiguration {

        @Bean
        @ConditionalOnMissingBean
        public HttpClient gatewayHttpClient(HttpClientProperties properties, List<HttpClientCustomizer> customizers) {
            Pool pool = properties.getPool();
            ConnectionProvider connectionProvider;
            if (pool.getType() == PoolType.DISABLED) {
                connectionProvider = ConnectionProvider.newConnection();
            } else if (pool.getType() == PoolType.FIXED) {
                connectionProvider = ConnectionProvider.fixed(pool.getName(), pool.getMaxConnections(), pool.getAcquireTimeout(), pool.getMaxIdleTime(), pool.getMaxLifeTime());
            } else {
                connectionProvider = ConnectionProvider.elastic(pool.getName(), pool.getMaxIdleTime(), pool.getMaxLifeTime());
            }

            HttpClient httpClient = HttpClient.create(connectionProvider).httpResponseDecoder((spec) -> {
                if (properties.getMaxHeaderSize() != null) {
                    spec.maxHeaderSize((int)properties.getMaxHeaderSize().toBytes());
                }

                if (properties.getMaxInitialLineLength() != null) {
                    spec.maxInitialLineLength((int)properties.getMaxInitialLineLength().toBytes());
                }

                return spec;
            }).tcpConfiguration((tcpClient) -> {
                if (properties.getConnectTimeout() != null) {
                    tcpClient = tcpClient.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, properties.getConnectTimeout());
                }

                Proxy proxy = properties.getProxy();
                if (StringUtils.hasText(proxy.getHost())) {
                    tcpClient = tcpClient.proxy((proxySpec) -> {
                        Builder builder = proxySpec.type(reactor.netty.tcp.ProxyProvider.Proxy.HTTP).host(proxy.getHost());
                        PropertyMapper map = PropertyMapper.get();
                        proxy.getClass();
                        map.from(proxy::getPort).whenNonNull().to(builder::port);
                        proxy.getClass();
                        map.from(proxy::getUsername).whenHasText().to(builder::username);
                        proxy.getClass();
                        map.from(proxy::getPassword).whenHasText().to((password) -> {
                            builder.password((s) -> {
                                return password;
                            });
                        });
                        proxy.getClass();
                        map.from(proxy::getNonProxyHostsPattern).whenHasText().to(builder::nonProxyHosts);
                    });
                }

                return tcpClient;
            });
            Ssl ssl = properties.getSsl();
            if (ssl.getKeyStore() != null && ssl.getKeyStore().length() > 0 || ssl.getTrustedX509CertificatesForTrustManager().length > 0 || ssl.isUseInsecureTrustManager()) {
                httpClient = httpClient.secure((sslContextSpec) -> {
                    SslContextBuilder sslContextBuilder = SslContextBuilder.forClient();
                    X509Certificate[] trustedX509Certificates = ssl.getTrustedX509CertificatesForTrustManager();
                    if (trustedX509Certificates.length > 0) {
                        sslContextBuilder = sslContextBuilder.trustManager(trustedX509Certificates);
                    } else if (ssl.isUseInsecureTrustManager()) {
                        sslContextBuilder = sslContextBuilder.trustManager(InsecureTrustManagerFactory.INSTANCE);
                    }

                    try {
                        sslContextBuilder = sslContextBuilder.keyManager(ssl.getKeyManagerFactory());
                    } catch (Exception var6) {
                        this.logger.error(var6);
                    }

                    sslContextSpec.sslContext(sslContextBuilder).defaultConfiguration(ssl.getDefaultConfigurationType()).handshakeTimeout(ssl.getHandshakeTimeout()).closeNotifyFlushTimeout(ssl.getCloseNotifyFlushTimeout()).closeNotifyReadTimeout(ssl.getCloseNotifyReadTimeout());
                });
            }

            if (properties.isWiretap()) {
                httpClient = httpClient.wiretap(true);
            }

            if (!CollectionUtils.isEmpty(customizers)) {
                customizers.sort(AnnotationAwareOrderComparator.INSTANCE);

                HttpClientCustomizer customizer;
                for(Iterator var7 = customizers.iterator(); var7.hasNext(); httpClient = customizer.customize(httpClient)) {
                    customizer = (HttpClientCustomizer)var7.next();
                }
            }

            return httpClient;
        }

    }    

　　　这样服务在启动的时候就会优先加载自定的 httpClient 实例。