spring-cloud-gateway使用https注意事项2---如何在转发后端服务的时候使用http

首先gateway代替nginx需要具备nginx的能力，所以https也跑不了，但使用后发现在loadbalance的时候调用微服务节点也是https，这样就会导致每开发一个服务就需要加一次证书，这就很尴尬。
基于该问题，所以我们需要gateway对前端是https，对后端是http
通过源码发现

/*
 * Copyright 2013-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package org.springframework.cloud.gateway.filter;

import java.net.URI;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.gateway.support.NotFoundException;
import org.springframework.core.Ordered;
import org.springframework.web.server.ServerWebExchange;

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR;
import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;

import reactor.core.publisher.Mono;

/**
 * @author Spencer Gibb
 * @author Tim Ysewyn
 */
public class LoadBalancerClientFilter implements GlobalFilter, Ordered {

    private static final Log log = LogFactory.getLog(LoadBalancerClientFilter.class);
    public static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10100;

    private final LoadBalancerClient loadBalancer;

    public LoadBalancerClientFilter(LoadBalancerClient loadBalancer) {
        this.loadBalancer = loadBalancer;
    }

    @Override
    public int getOrder() {
        return LOAD_BALANCER_CLIENT_FILTER_ORDER;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        URI url = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
        String schemePrefix = exchange.getAttribute(GATEWAY_SCHEME_PREFIX_ATTR);
        if (url == null || (!"lb".equals(url.getScheme()) && !"lb".equals(schemePrefix))) {
            return chain.filter(exchange);
        }
        //preserve the original url
        addOriginalRequestUrl(exchange, url);

        log.trace("LoadBalancerClientFilter url before: " + url);

        final ServiceInstance instance = loadBalancer.choose(url.getHost());

        if (instance == null) {
            throw new NotFoundException("Unable to find instance for " + url.getHost());
        }

        URI uri = exchange.getRequest().getURI();

        // if the `lb:<scheme>` mechanism was used, use `<scheme>` as the default,
        // if the loadbalancer doesn't provide one.
        String overrideScheme = null;
        if (schemePrefix != null) {
            overrideScheme = url.getScheme();
        }

        URI requestUrl = loadBalancer.reconstructURI(new DelegatingServiceInstance(instance, overrideScheme), uri);

        log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
        exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
        return chain.filter(exchange);
    }

    class DelegatingServiceInstance implements ServiceInstance {
        final ServiceInstance delegate;
        private String overrideScheme;

        DelegatingServiceInstance(ServiceInstance delegate, String overrideScheme) {
            this.delegate = delegate;
            this.overrideScheme = overrideScheme;
        }

        @Override
        public String getServiceId() {
            return delegate.getServiceId();
        }

        @Override
        public String getHost() {
            return delegate.getHost();
        }

        @Override
        public int getPort() {
            return delegate.getPort();
        }

        @Override
        public boolean isSecure() {
            return delegate.isSecure();
        }

        @Override
        public URI getUri() {
            return delegate.getUri();
        }

        @Override
        public Map<String, String> getMetadata() {
            return delegate.getMetadata();
        }

        @Override
        public String getScheme() {
            String scheme = delegate.getScheme();
            if (scheme != null) {
                return scheme;
            }
            return this.overrideScheme;
        }

    }
}

URI requestUrl = loadBalancer.reconstructURI(new DelegatingServiceInstance(instance, overrideScheme), uri);
这句是对lb的http请求的一个封装，scheme就是你用的是什么他就用什么，
而且他没有给留修改的入口。所以我想到在这个过滤器之后紧跟着他，把他
exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
放入的URL里的scheme修改掉。
我们进入reconstructURI这个代码发现是一个接口：

/**
     * Create a proper URI with a real host and port for systems to utilize.
     * Some systems use a URI with the logical serivce name as the host,
     * such as http://myservice/path/to/service.  This will replace the
     * service name with the host:port from the ServiceInstance.
     * @param instance
     * @param original a URI with the host as a logical service name
     * @return a reconstructed URI
     */
    URI reconstructURI(ServiceInstance instance, URI original);

继续找到他的实现类:

/*
 * Copyright 2013-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.netflix.ribbon;

import java.io.IOException;
import java.net.URI;
import java.util.Collections;
import java.util.Map;

import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.Server;

import org.springframework.cloud.client.DefaultServiceInstance;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.client.loadbalancer.LoadBalancerRequest;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;

import static org.springframework.cloud.netflix.ribbon.RibbonUtils.updateToSecureConnectionIfNeeded;

/**
 * @author Spencer Gibb
 * @author Dave Syer
 * @author Ryan Baxter
 * @author Tim Ysewyn
 */
public class RibbonLoadBalancerClient implements LoadBalancerClient {

    private SpringClientFactory clientFactory;

    public RibbonLoadBalancerClient(SpringClientFactory clientFactory) {
        this.clientFactory = clientFactory;
    }

    @Override
    public URI reconstructURI(ServiceInstance instance, URI original) {
        Assert.notNull(instance, "instance can not be null");
        String serviceId = instance.getServiceId();
        RibbonLoadBalancerContext context = this.clientFactory
                .getLoadBalancerContext(serviceId);

        URI uri;
        Server server;
        if (instance instanceof RibbonServer) {
            RibbonServer ribbonServer = (RibbonServer) instance;
            server = ribbonServer.getServer();
            uri = updateToSecureConnectionIfNeeded(original, ribbonServer);
        } else {
            server = new Server(instance.getScheme(), instance.getHost(), instance.getPort());
            IClientConfig clientConfig = clientFactory.getClientConfig(serviceId);
            ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
            uri = updateToSecureConnectionIfNeeded(original, clientConfig,
                    serverIntrospector, server);
        }
        return context.reconstructURIWithServer(server, uri);
    }

    @Override
    public ServiceInstance choose(String serviceId) {
        Server server = getServer(serviceId);
        if (server == null) {
            return null;
        }
        return new RibbonServer(serviceId, server, isSecure(server, serviceId),
                serverIntrospector(serviceId).getMetadata(server));
    }

    @Override
    public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
        ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
        Server server = getServer(loadBalancer);
        if (server == null) {
            throw new IllegalStateException("No instances available for " + serviceId);
        }
        RibbonServer ribbonServer = new RibbonServer(serviceId, server, isSecure(server,
                serviceId), serverIntrospector(serviceId).getMetadata(server));

        return execute(serviceId, ribbonServer, request);
    }

    @Override
    public <T> T execute(String serviceId, ServiceInstance serviceInstance, LoadBalancerRequest<T> request) throws IOException {
        Server server = null;
        if(serviceInstance instanceof RibbonServer) {
            server = ((RibbonServer)serviceInstance).getServer();
        }
        if (server == null) {
            throw new IllegalStateException("No instances available for " + serviceId);
        }

        RibbonLoadBalancerContext context = this.clientFactory
                .getLoadBalancerContext(serviceId);
        RibbonStatsRecorder statsRecorder = new RibbonStatsRecorder(context, server);

        try {
            T returnVal = request.apply(serviceInstance);
            statsRecorder.recordStats(returnVal);
            return returnVal;
        }
        // catch IOException and rethrow so RestTemplate behaves correctly
        catch (IOException ex) {
            statsRecorder.recordStats(ex);
            throw ex;
        }
        catch (Exception ex) {
            statsRecorder.recordStats(ex);
            ReflectionUtils.rethrowRuntimeException(ex);
        }
        return null;
    }

    private ServerIntrospector serverIntrospector(String serviceId) {
        ServerIntrospector serverIntrospector = this.clientFactory.getInstance(serviceId,
                ServerIntrospector.class);
        if (serverIntrospector == null) {
            serverIntrospector = new DefaultServerIntrospector();
        }
        return serverIntrospector;
    }

    private boolean isSecure(Server server, String serviceId) {
        IClientConfig config = this.clientFactory.getClientConfig(serviceId);
        ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
        return RibbonUtils.isSecure(config, serverIntrospector, server);
    }

    protected Server getServer(String serviceId) {
        return getServer(getLoadBalancer(serviceId));
    }

    protected Server getServer(ILoadBalancer loadBalancer) {
        if (loadBalancer == null) {
            return null;
        }
        return loadBalancer.chooseServer("default"); // TODO: better handling of key
    }

    protected ILoadBalancer getLoadBalancer(String serviceId) {
        return this.clientFactory.getLoadBalancer(serviceId);
    }

    public static class RibbonServer implements ServiceInstance {
        private final String serviceId;
        private final Server server;
        private final boolean secure;
        private Map<String, String> metadata;

        public RibbonServer(String serviceId, Server server) {
            this(serviceId, server, false, Collections.<String, String> emptyMap());
        }

        public RibbonServer(String serviceId, Server server, boolean secure,
                Map<String, String> metadata) {
            this.serviceId = serviceId;
            this.server = server;
            this.secure = secure;
            this.metadata = metadata;
        }

        @Override
        public String getServiceId() {
            return this.serviceId;
        }

        @Override
        public String getHost() {
            return this.server.getHost();
        }

        @Override
        public int getPort() {
            return this.server.getPort();
        }

        @Override
        public boolean isSecure() {
            return this.secure;
        }

        @Override
        public URI getUri() {
            return DefaultServiceInstance.getUri(this);
        }

        @Override
        public Map<String, String> getMetadata() {
            return this.metadata;
        }

        public Server getServer() {
            return this.server;
        }

        @Override
        public String getScheme() {
            return this.server.getScheme();
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("RibbonServer{");
            sb.append("serviceId='").append(serviceId).append('\'');
            sb.append(", server=").append(server);
            sb.append(", secure=").append(secure);
            sb.append(", metadata=").append(metadata);
            sb.append('}');
            return sb.toString();
        }
    }

}

其中用到了RibbonUtils中的upgradeConnection这个方法

private static URI upgradeConnection(URI uri, String scheme) {
        UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromUri(uri).scheme(scheme);
        if (uri.getRawQuery() != null) {
            // When building the URI, UriComponentsBuilder verify the allowed characters and does not
            // support the '+' so we replace it for its equivalent '%20'.
            // See issue https://jira.spring.io/browse/SPR-10172
            uriComponentsBuilder.replaceQuery(uri.getRawQuery().replace("+", "%20"));
        }
        return uriComponentsBuilder.build(true).toUri();
    }

由于他是私有的方法，于是乎把他拷贝过来，更新他的url把https变成http

package net.youqu.micro.service.filter;

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.util.UriComponentsBuilder;
import reactor.core.publisher.Mono;

import java.net.URI;

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;

/**
 * description:
 *
 * @author wangpeng
 * @date 2018/06/14
 */
@Component
public class SchemeFilter implements GlobalFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        Object uriObj = exchange.getAttributes().get(GATEWAY_REQUEST_URL_ATTR);
        if (uriObj != null) {
            URI uri = (URI) uriObj;
            uri = this.upgradeConnection(uri, "http");
            exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, uri);
        }
        return chain.filter(exchange);
    }

    private URI upgradeConnection(URI uri, String scheme) {
        UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromUri(uri).scheme(scheme);
        if (uri.getRawQuery() != null) {
            // When building the URI, UriComponentsBuilder verify the allowed characters and does not
            // support the '+' so we replace it for its equivalent '%20'.
            // See issue https://jira.spring.io/browse/SPR-10172
            uriComponentsBuilder.replaceQuery(uri.getRawQuery().replace("+", "%20"));
        }
        return uriComponentsBuilder.build(true).toUri();
    }

    @Override
    public int getOrder() {
        return 10101;
    }
}

LoadBalancerClientFilter的order是10100，所以我们的order是10101紧跟着他，嘿嘿。
大功告成！！！