一、概述 

版本说明：SpringBoot2：2.0.5.RELEASE，Spring Cloud.Finchley版；

说明：Spring Cloud Gateway替换Zuul的时候发现Swagger并不支持以WebFlux为底层的Gateway，无法集成，运行报错;

二、网关配置

2.1 pom文件:

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-web</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <!--spring cloud gateway 不兼容 spring-boot-starter-web-->
        <!--<dependency>-->
        <!--<groupId>org.springframework.boot</groupId>-->
        <!--<artifactId>spring-boot-starter-web</artifactId>-->
        <!--</dependency>-->

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.58</version>
        </dependency>
        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>
        <!--swagger2-->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>
        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>swagger-bootstrap-ui</artifactId>
            <version>1.9.3</version>
        </dependency>
    </dependencies>

 2.2 网关properties.yml文件:

spring:
  profiles:
    active: dev
  application:
    name: gateway-service
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
          # 服务名小写
          lower-case-service-id: true
      routes:
        - id: sso-service
          # lb代表从注册中心获取服务，且已负载均衡方式转发
          uri: lb://sso-service
          predicates:
            - Path=/sso/**
          # 加上StripPrefix=1，否则转发到后端服务时会带上consumer前缀
          filters:
            - SwaggerHeaderFilter
            - StripPrefix=1
            - AddResponseHeader=X-Response-Default-Foo, Default-Bar
        - id: sys-service
          # lb代表从注册中心获取服务，且已负载均衡方式转发
          uri: lb://sys-service
          predicates:
            - Path=/sys/**
            # 加上StripPrefix=1，否则转发到后端服务时会带上consumer前缀
          filters:
            - SwaggerHeaderFilter
            - StripPrefix=1
        # 路由到百度页面
        - id: baidu_route
          uri: http://www.baidu.com
          predicates:
            - Path=/baidu/**
          filters:
            - SwaggerHeaderFilter
            - StripPrefix=1

三、关键代码

3.1 SwaggerHandler.java

说明：因为Gateway里没有配置SwaggerConfig，而运行Swagger-ui又需要依赖一些接口，所以我的想法是自己建立相应的swagger-resource端点。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Mono;
import springfox.documentation.swagger.web.*;

import java.util.Optional;

@RestController
@RequestMapping("/swagger-resources")
public class SwaggerHandler {
    @Autowired(required = false)
    private SecurityConfiguration securityConfiguration;
    @Autowired(required = false)
    private UiConfiguration uiConfiguration;
    private final SwaggerResourcesProvider swaggerResources;

    @Autowired
    public SwaggerHandler(SwaggerResourcesProvider swaggerResources) {
        this.swaggerResources = swaggerResources;
    }


    @GetMapping("/configuration/security")
    public Mono<ResponseEntity<SecurityConfiguration>> securityConfiguration() {
        return Mono.just(new ResponseEntity<>(
                Optional.ofNullable(securityConfiguration).orElse(SecurityConfigurationBuilder.builder().build()), HttpStatus.OK));
    }

    @GetMapping("/configuration/ui")
    public Mono<ResponseEntity<UiConfiguration>> uiConfiguration() {
        return Mono.just(new ResponseEntity<>(
                Optional.ofNullable(uiConfiguration).orElse(UiConfigurationBuilder.builder().build()), HttpStatus.OK));
    }

    @GetMapping("")
    public Mono<ResponseEntity> swaggerResources() {
        return Mono.just((new ResponseEntity<>(swaggerResources.get(), HttpStatus.OK)));
    }
}

3.2 SwaggerProvider.java

说明：因为Swagger暂不支持webflux项目，所以Gateway里不能配置SwaggerConfig，也就是说Gateway无法提供自身API。所以这里的集成只是基于基于WebMvc的微服务项目。 

配置SwaggerProvider，获取Api-doc，即SwaggerResources。

import lombok.AllArgsConstructor;
import org.springframework.cloud.gateway.support.NameUtils;
import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Component;
import springfox.documentation.swagger.web.SwaggerResource;
import springfox.documentation.swagger.web.SwaggerResourcesProvider;
import org.springframework.cloud.gateway.config.GatewayProperties;
import org.springframework.cloud.gateway.route.RouteLocator;

import java.util.ArrayList;
import java.util.List;



/**
 * @ClassName: SwaggerProvider
 * @Description: 聚合接口文档注册
 **/
@Component
@Primary
@AllArgsConstructor
public class SwaggerProvider implements SwaggerResourcesProvider {
    //v2/api-docs
    public static final String API_URI = "/v2/api-docs";
    private final RouteLocator routeLocator;
    private final GatewayProperties gatewayProperties;


    @Override
    public List<SwaggerResource> get() {
        List<SwaggerResource> resources = new ArrayList<>();
        List<String> routes = new ArrayList<>();
        /**
         * 获取Gateway配置文件的route参数
         */
        routeLocator.getRoutes().subscribe(route -> routes.add(route.getId()));
        /**
         * 结合配置的route-path和route过滤，只获取有效的route节点
         */
        gatewayProperties.getRoutes().stream().filter(routeDefinition -> routes.contains(routeDefinition.getId()))
                .forEach(routeDefinition -> routeDefinition.getPredicates().stream()
                        .filter(predicateDefinition -> ("Path").equalsIgnoreCase(predicateDefinition.getName()))
                        .forEach(predicateDefinition -> resources.add(swaggerResource(routeDefinition.getId(),
                                predicateDefinition.getArgs().get(NameUtils.GENERATED_NAME_PREFIX + "0")
                                        .replace("/**", API_URI)))));

        return resources;
    }

    private SwaggerResource swaggerResource(String name, String location) {
        SwaggerResource swaggerResource = new SwaggerResource();
        swaggerResource.setName(name);
        swaggerResource.setLocation(location);
        swaggerResource.setSwaggerVersion("2.0");
        return swaggerResource;
    }
}

3.3 SwaggerHeaderFilter.java

说明：【Spring Boot版本超过2.0.6的应该可以跳过这一步，最新源码也更新了。Spring修复了bug给我们添加上了这个Header】另外，我发现在路由为sys/test/{a}/{b}，在swagger会显示为test/{a}/{b}，缺少了sys这个路由节点。断点源码时发现在Swagger中会根据X-Forwarded-Prefix这个Header来获取BasePath，将它添加至接口路径与host中间，这样才能正常做接口测试，而Gateway在做转发的时候并没有这个Header添加进Request，所以发生接口调试的404错误。解决思路是在Gateway里加一个过滤器来添加这个header。

import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import org.springframework.web.server.ServerWebExchange;


@Component
public class SwaggerHeaderFilter extends AbstractGatewayFilterFactory {
    private static final String HEADER_NAME = "X-Forwarded-Prefix";

    @Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            ServerHttpRequest request = exchange.getRequest();
            String path = request.getURI().getPath();
            if (!StringUtils.endsWithIgnoreCase(path, SwaggerProvider.API_URI)) {
                return chain.filter(exchange);
            }
            String basePath = path.substring(0, path.lastIndexOf(SwaggerProvider.API_URI));
            ServerHttpRequest newRequest = request.mutate().header(HEADER_NAME, basePath).build();
            ServerWebExchange newExchange = exchange.mutate().request(newRequest).build();
            return chain.filter(newExchange);
        };
    }
}

四、访问

这时启动Gateway，访问gateway-ip:gateway-port/doc.html时，即可正常使用swagger；