Not able to get springfox-swagger-ui working with Spring MVC

Question

I have spent a few days looking and have been unable to find a solution, most example deal with spring boot and gradle, I am only using spring mvc and maven.

If I remove the springfox-swagger-ui dependency the app runs fine and the following return JSON as expected http:\\localhost:8080\restful\v2\api-docs?group=restful-api

For some reason my spring application is failing to pass the swagger-ui.html and it gives the same response if I set an index.html

I have tried adding:

1. Welcome list files in the web.xml
2. Resource Handlers
3. Default Servlet Handling

None worked.

App Config

package au.com.speak.restful.spring;

import org.springframework.context.MessageSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.ReloadableResourceBundleMessageSource;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import     org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.i18n.CookieLocaleResolver;
import org.springframework.web.servlet.i18n.LocaleChangeInterceptor;

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "au.com.speak.restful.api" })
public class AppConfig extends WebMvcConfigurerAdapter {

    // ========= Overrides ===========

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LocaleChangeInterceptor());
    }

    // ========= Beans ===========

    @Bean(name = "localeResolver")
    public LocaleResolver getLocaleResolver() {
        return new CookieLocaleResolver();
    }

    @Bean(name = "messageSource")
    public MessageSource getMessageSources() {
        ReloadableResourceBundleMessageSource messageSource = new     ReloadableResourceBundleMessageSource();
        messageSource.setBasenames("/WEB-INF/resources/properties/error", "/WEB-INF/resources/properties/validation");
        messageSource.setCacheSeconds(0);

        return messageSource;
    }
}

Swagger Config

package au.com.speak.restful.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@Configuration
@EnableSwagger2
public class SwaggerConfig  {

    @Bean
    public Docket restfulApi() {
        return new Docket(DocumentationType.SWAGGER_2)
                .groupName("restful-api")
                .select()
                .build()
                .apiInfo(apiInfo());
    }

    private ApiInfo apiInfo() {

        ApiInfo apiInfo = new ApiInfo(
                "My Apps API Title",
                "My Apps API Description",
                "My Apps API Version",
                "My Apps API terms of service",
                "My Apps API Contact Email",
                "My Apps API Licence Type",
                "My Apps API License URL"
        );
        return apiInfo;
    }
}

The code I have is as follows:

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee     http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

    <display-name>example restful api</display-name>

    <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>

    <listener>
        <listener-class>
            org.springframework.security.web.session.HttpSessionEventPublisher
        </listener-class>
    </listener>

    <listener>
        <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
    </listener>

    <context-param>
        <param-name>contextClass</param-name>
        <param-value>                    org.springframework.web.context.support.AnnotationConfigWebApplicationContext
        </param-value>
    </context-param>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            au.com.speak.restful.spring.AppConfig
            au.com.speak.restful.spring.PropertyConfig
            au.com.speak.restful.spring.SecurityConfig
            au.com.speak.restful.spring.ServiceConfig
            au.com.speak.restful.spring.PersistenceConfig
            au.com.speak.restful.spring.SwaggerConfig
        </param-value>
    </context-param>

    <context-param>
        <param-name>log4jConfigLocation</param-name>
        <param-value>classpath:log4j.xml</param-value>
    </context-param>

    <!--
        Reads request input using UTF-8 encoding
    -->
    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!--
        Apply Spring Security Filter to all Requests
     -->
    <filter>
        <filter-name>springSecurityFilterChain</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>springSecurityFilterChain</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!--
        Handles all requests into the application
    -->
    <servlet>
        <servlet-name>model</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>*</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>model</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

Error

2015-04-27 23:03:47,805 INFO   - Loading XML bean definitions from ServletContext resource [/swagger-ui.html]
2015-04-27 23:03:47,811 ERROR  - Context initialization failed
org.springframework.beans.factory.xml.XmlBeanDefinitionStoreException: Line 2 in XML document from ServletContext resource [/swagger-ui.html] is invalid; nested exception is org.xml.sax.SAXParseException; lineNumber: 2; columnNumber: 7;  Element type "html" must be declared.
at   org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:399)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:336)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:304)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:181)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:217)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:188)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:129)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:537)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:452)
at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:663)
at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:629)
at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:677)
at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:548)
at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:489)
at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
at javax.servlet.GenericServlet.init(GenericServlet.java:158)
at  org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1231)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1031)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4913)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5200)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1618)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:463)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:413)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1466)
at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:76)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1307)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1399)
at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:828)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:323)
at sun.rmi.transport.Transport$1.run(Transport.java:200)
at sun.rmi.transport.Transport$1.run(Transport.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:196)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:568)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:826)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$240(TCPTransport.java:683)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$1/1746485750.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:682)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at     java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: org.xml.sax.SAXParseException; lineNumber: 2; columnNumber: 7;     Element type "html" must be declared.
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:437)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:325)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.handleStartElement(XMLDTDValidator.java:1906)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidator.java:742)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1363)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$ContentDriver.scanRootElementHook(XMLDocumentScannerImpl.java:1292)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3138)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:880)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:348)
at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:76)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadDocument(XmlBeanDefinitionReader.java:429)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
... 66 more

Answer 1

Fixed by adding the following into the AppConfig.

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry
        .addResourceHandler("swagger-ui.html")
        .addResourceLocations("classpath:/META-INF/resources/");
    registry
        .addResourceHandler("/webjars/**")
        .addResourceLocations("classpath:/META-INF/resources/webjars/");
}

Answer 2

I encountered this error because of a version mismatch between springfox-swagger2 and springfox-swagger-ui, versions of the two dependencies have to be the same.

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
    <version>2.6.1</version>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger-ui</artifactId>
    <version>2.6.1</version>
</dependency>

Answer 3

I don't know how different the new version of swagger is but I am using version 1.0.2. I am also using swagger-spring-mvc-ui-0.4.jar to get the swagger API jsp file and css.

Maven dependency

    <dependency>
        <groupId>com.mangofactory</groupId>
        <artifactId>swagger-springmvc</artifactId>
        <version>1.0.2</version>
    </dependency>

I am using it along with Spring MVC 4.1.5. Below is the only file that I am using to generate swagger api json file.

SwaggerConfig.java

import static org.ajar.swaggermvcui.SwaggerSpringMvcUi.WEB_JAR_RESOURCE_LOCATION;
import static org.ajar.swaggermvcui.SwaggerSpringMvcUi.WEB_JAR_RESOURCE_PATTERNS;
import static org.ajar.swaggermvcui.SwaggerSpringMvcUi.WEB_JAR_VIEW_RESOLVER_PREFIX;
import static org.ajar.swaggermvcui.SwaggerSpringMvcUi.WEB_JAR_VIEW_RESOLVER_SUFFIX;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

import com.mangofactory.swagger.configuration.SpringSwaggerConfig;
import com.mangofactory.swagger.models.dto.ApiInfo;
import com.mangofactory.swagger.plugin.EnableSwagger;
import com.mangofactory.swagger.plugin.SwaggerSpringMvcPlugin;

@EnableSwagger
public class SwaggerConfig extends WebMvcConfigurerAdapter {
    private SpringSwaggerConfig springSwaggerConfig;

    @Autowired
    public void setSpringSwaggerConfig(SpringSwaggerConfig springSwaggerConfig) {
        this.springSwaggerConfig = springSwaggerConfig;
    }

    @Bean
    public SwaggerSpringMvcPlugin customImplementation() {
        this.springSwaggerConfig.defaultSwaggerPathProvider()
                .setApiResourcePrefix("api");
        return new SwaggerSpringMvcPlugin(this.springSwaggerConfig)
                .apiInfo(apiInfo());// .includePatterns(".*swagger.*");
    }

    private ApiInfo apiInfo() {
        ApiInfo apiInfo = new ApiInfo("My APIs",
                "RESTful APIs available under My Portal", "#",
                "deepankarsirt@gmail.com", "License Information", "#");
        return apiInfo;
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler(WEB_JAR_RESOURCE_PATTERNS)
                .addResourceLocations(WEB_JAR_RESOURCE_LOCATION)
                .setCachePeriod(0);
    }

    @Bean
    public InternalResourceViewResolver getInternalResourceViewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix(WEB_JAR_VIEW_RESOLVER_PREFIX);
        resolver.setSuffix(WEB_JAR_VIEW_RESOLVER_SUFFIX);
        return resolver;
    }

    @Override
    public void configureDefaultServletHandling(
            DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
}

My Rest Controller

@RestController
@RequestMapping(produces = MediaType.APPLICATION_JSON_VALUE)
public class CommonUtilityServices {

    @Autowired
    private CommonUtilityService commonUtilityService;

    @ApiOperation(value = "Is Unique", notes = "This service checks if a value is already present in DB or not.<br>Below is the sample JSON object. <br> <pre><code class=\"json\">{<span class=\"attribute\"><span class=\"attribute\">\"dbField\"</span></span> : <span class=\"value\"><span class=\"string\"><span class=\"value\"><span class=\"string\">\"organization.name\"</span></span></span></span>, <span class=\"attribute\"><span class=\"attribute\">\"fieldValue\" : <span class=\"value\"><span class=\"string\"><span class=\"value\"><span class=\"string\">\"novopay\"</span></span></span></span>}</code></pre><br>'dbField' accepts value 'tableDB.DBField' format.<br>'fieldValue' is the value needs to be check for uniqueness.")
    @ApiResponses(value = {
            @ApiResponse(code = 202, message = "Request Accepted"),
            @ApiResponse(code = 400, message = "Bad Request") })
    @RequestMapping(value = "/isUnique", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
    public @ResponseBody ResponseEntity<Boolean> isUnique(
            HttpServletRequest request, @RequestBody String jsonStr) {
        try {
            ObjectMapper mapper = new ObjectMapper();
            Map<?, ?> myMap = mapper.readValue(jsonStr.toString(),
                    HashMap.class);
            String dbField = (String) myMap.get("dbField");
            String fieldValue = (String) myMap.get("fieldValue");
            String whereClause = (String) myMap.get("whereClause");
            return new ResponseEntity<Boolean>(
                    commonUtilityService
                            .isValueAlreadyInDB(dbField, fieldValue, whereClause),
                    HttpStatus.ACCEPTED);
        } catch (IOException | RuntimeException e) {
            return new ResponseEntity<Boolean>(HttpStatus.BAD_REQUEST);
        }
    }}

Apart from all above changes, I have made a local copy of sdoc.jsp file available in swagger-spring-mvc-ui-0.4.jar and changed the url it was pointing by default.

<script type="text/javascript">
$(function() {
    window.swaggerUi = new SwaggerUi({
        url: "/portal/api/api-docs", //New URL
        dom_id: "swagger-ui-container",
        supportedSubmitMethods: ['get', 'post', 'put', 'delete'],
        onComplete: function(swaggerApi, swaggerUi) {
            log("Loaded SwaggerUI");

Please note that I don't have any change in web.xml file and the SwaggerConfig Class is getting loaded using spring annotations/component-scan

Answer 4

Although the author of the question doesn't use Spring Boot - I decided to post here to help others that do. For me with Spring 5.0.0.M5 using Spring Security and Spring Boot It worked by adding those two dependencies in my pom.xml:

 <dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
    <version>2.6.1</version>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger-ui</artifactId>
    <version>2.6.1</version>
</dependency>

then in my SpringBootApp class I added the swagger annotation and a corresponding Bean:

@SpringBootApplication
@EnableSwagger2
public class SpringBootApp extends WebMvcConfigurerAdapter {
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.any())
                .paths(PathSelectors.any())
                .build();
    }

    [...]
}

After that the api documentation is available on my app root which happens to be /: http://localhost:8080/swagger-ui.html

With this way you don't even need a separate SwaggerConfig as described here: http://www.baeldung.com/swagger-2-documentation-for-spring-rest-api

Answer 5

I encountered this problem with Swagger 3.0.0 and Spring Boot 2.2.4.

The problem I found was that io.springfox:springfox-boot-starter:3.0.0 includes io.springfox:springfox-swagger2:jar:2.9.2. I explicitly included this dependency from springfox-boot-starter and included the 3.0.0 version of springfox-swagger2:

<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-boot-starter</artifactId>
  <version>3.0.0</version>
  <exclusions>
    <exclusion>
      <groupId>io.springfox</groupId>
      <artifactId>springfox-swagger2</artifactId>
    </exclusion>
  </exclusions>
</dependency>
<dependency>
  <groupId>io.springfox</groupId>
  <artifactId>springfox-swagger2</artifactId>
  <version>3.0.0</version>
</dependency>

This resolved the CNFE.