无法在spring应用程序中使用swagger

<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>

@Configuration
@EnableSwagger2
public class SwaggerConfig {
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.basePackage("com.example.controller"))
                .paths(PathSelectors.any())
                .build();
    }
}

@RestController
@RequestMapping("/api")
@Api(tags = "User API")
public class UserController {
    @GetMapping("/users")
    @ApiOperation("Get all users")
    public List<User> getUsers() {
        // ...
    }
}

@Configuration
@EnableSwagger2
public class SwaggerConfig {
    // ...

    @Bean
    public WebMvcConfigurerAdapter forwardSwaggerToIndexHtml() {
        return new WebMvcConfigurerAdapter() {
            @Override
            public void addViewControllers(ViewControllerRegistry registry) {
                registry.addViewController("/swagger-ui/")
                        .setViewName("forward:/swagger-ui/index.html");
            }
        };
    }
}