目前swagger3.0已经发布，功能更加强大，并且向下兼容，支持WebFlux，所以使用gateway时完美兼容。
为了美化swagger界面引入三方依赖，详情

1.网关模块聚合swagger

引入相关依赖

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-boot-starter</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>com.github.xiaoymin</groupId>
    <artifactId>knife4j-spring-boot-starter</artifactId>
    <version>2.0.6</version>
</dependency>

新建SwaggerConfig类，暴露网关服务文档

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.builders.RequestParameterBuilder;
import springfox.documentation.oas.annotations.EnableOpenApi;
import springfox.documentation.schema.ScalarType;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.service.ParameterType;
import springfox.documentation.service.RequestParameter;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;

import java.util.Collections;
import java.util.List;

@Configuration
@EnableOpenApi
public class SwaggerConfig {

    @Bean
    public Docket createRestApi() {
        return new Docket(DocumentationType.OAS_30)
                .select()
                .apis(RequestHandlerSelectors.basePackage("com.xxx"))
                .paths(PathSelectors.any())
                .build()
                .globalRequestParameters(globalRequestParameters())
                .apiInfo(apiInfo());
    }

    private List<RequestParameter> globalRequestParameters() {
        RequestParameterBuilder parameterBuilder = new RequestParameterBuilder().in(ParameterType.HEADER).name("Token").required(false).query(param -> param.model(model -> model.scalarModel(ScalarType.STRING)));
        return Collections.singletonList(parameterBuilder.build());
    }

    private ApiInfo apiInfo() {
        return new ApiInfoBuilder()
                .title("gateway服务API")
                .description("gateway接口文档")
                .termsOfServiceUrl("http://127.0.0.1:8100/")
                .version("1.0.0")
                .build();
    }
}

新建一个SwaggerProvider类，聚合其他服务文档

import lombok.AllArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.gateway.config.GatewayProperties;
import org.springframework.cloud.gateway.route.RouteLocator;
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 java.util.ArrayList;
import java.util.List;

@Slf4j
@Component
@Primary
@AllArgsConstructor
public class SwaggerProvider implements SwaggerResourcesProvider {

    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<>();
        routeLocator.getRoutes().subscribe(route -> routes.add(route.getId()));
        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) {
        log.info("name : [{}], location : [{}]",name,location);
        SwaggerResource swaggerResource = new SwaggerResource();
        swaggerResource.setName(name);
        swaggerResource.setLocation(location);
        swaggerResource.setSwaggerVersion("2.0");
        return swaggerResource;
    }
}

新建一个SwaggerResourceController类，提供swagger资源请求

import com.glorious.config.SwaggerProvider;
import io.swagger.annotations.Api;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
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.List;
import java.util.Optional;

@Api(value = "/swagger-resources")
@RestController
@RequestMapping("/swagger-resources")
public class SwaggerResourceController {

    @Autowired(required = false)
    private SecurityConfiguration securityConfiguration;

    @Autowired(required = false)
    private UiConfiguration uiConfiguration;

    private final SwaggerProvider swaggerProvider;

    @Autowired
    public SwaggerResourceController(SwaggerProvider swaggerProvider) {
        this.swaggerProvider = swaggerProvider;
    }

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

    @RequestMapping
    public Mono<ResponseEntity<List<SwaggerResource>>> swaggerResources() {
        return Mono.just((new ResponseEntity<>(swaggerProvider.get(), HttpStatus.OK)));
    }
}

网关模块聚合swagger到此结束

2.服务模块聚合swagger

引入相关依赖

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-boot-starter</artifactId>
    <version>3.0.0</version>
</dependency>
<dependency>
    <groupId>com.github.xiaoymin</groupId>
    <artifactId>knife4j-micro-spring-boot-starter</artifactId>
    <version>3.0.1</version>
</dependency>

新建SwaggerConfig配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.builders.RequestParameterBuilder;
import springfox.documentation.oas.annotations.EnableOpenApi;
import springfox.documentation.schema.ScalarType;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.service.ParameterType;
import springfox.documentation.service.RequestParameter;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;

import java.util.Collections;
import java.util.List;

@Configuration
@EnableOpenApi
public class SwaggerConfig {
    
    @Bean
    public Docket createRestApi() {
        return new Docket(DocumentationType.OAS_30)
                .select()
                .apis(RequestHandlerSelectors.basePackage("com.xxx"))
                .paths(PathSelectors.any())
                .build()
                .globalRequestParameters(globalRequestParameters())
                .apiInfo(apiInfo());
    }

    private List<RequestParameter> globalRequestParameters() {
        RequestParameterBuilder parameterBuilder = new RequestParameterBuilder().in(ParameterType.HEADER).name("Token").required(false).query(param -> param.model(model -> model.scalarModel(ScalarType.STRING)));
        return Collections.singletonList(parameterBuilder.build());
    }
    
    private ApiInfo apiInfo() {
        return new ApiInfoBuilder()
                .title("xxx服务API")
                .description("xxx管理文档API")
                .termsOfServiceUrl("http://127.0.0.1:8200/")
                .version("1.0")
                .build();
    }
}

多个服务如此配置即可。

3.启动各个微服务，访问网关微服务IP加端口以及swagger地址后缀

http://localhost:8100/doc.html
http://localhost:8100/swagger-ui/index.html