Swagger Documentation with Spring Boot (working UI)

pom.xml

<!-- Spring boot version is 2.0.3.RELEASE-->

<dependencies>
  <!-- Swagger 2 Doc Dependency -->
  <dependency>
      <groupId>io.springfox</groupId>
      <artifactId>springfox-swagger2</artifactId>
      <version>2.9.2</version>
  </dependency>

  <!-- Swagger 2 UI -->
  <dependency>
      <groupId>io.springfox</groupId>
      <artifactId>springfox-swagger-ui</artifactId>
      <version>2.9.2</version>
  </dependency>
</dependencies>

SwaggerDocConfig.java

package com.example.springbootswagger.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.PropertySource;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import springfox.bean.validators.configuration.BeanValidatorPluginsConfiguration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
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 SwaggerDocConfig implements WebMvcConfigurer {

    @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/");
    }

    @Bean
    public Docket apiDocket() {

        return new Docket(DocumentationType.SWAGGER_2)
                .apiInfo(getApiInfo())
                .select()
                .apis(RequestHandlerSelectors.basePackage("com.example.springbootswagger.controller"))
                .paths(PathSelectors.any())
                .build();
    }

    private ApiInfo getApiInfo() {

        return new ApiInfoBuilder()
                .title("Swagger API Doc")
                .description("More description about the API")
                .version("1.0.0")
                .build();
    }
}

I'm not sure how this works. I had to use extends WebMvcConfigurerAdapter rather than implements WebMvcConfigurer