swagger2报错Unable to render this definition

前言

这个问题是第二次遇到了，索性就记录下来；

问题描述

Unable to render this definition
The provided definition does not specify a valid version field.
Please indicate a valid Swagger or OpenAPI version field. Supported version fields are swagger: "2.0" and those that match openapi: 3.0.n (for example, openapi: 3.0.0).

解决办法

查看接口返回api-docs信息

控制台报错：system.js:461 TypeError: Cannot convert undefined or null to object

接口api-docs返回信息未正确解析导致；

添加mvc配置

@Configuration
@EnableWebMvc
public class MvcConfiguration implements WebMvcConfigurer {

    @Bean
    public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        converter.setObjectMapper(objectMapper());
        return converter;
    }

    @Bean
    ObjectMapper objectMapper(){
        ObjectMapper om = new ObjectMapper();
        om.setSerializationInclusion(JsonInclude.Include.ALWAYS);
        // 设置 SerializationFeature.FAIL_ON_EMPTY_BEANS 为 false
        om.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
        om.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
        return om;
    }

    /**
     * 防止@EnableMvc把默认的静态资源路径覆盖了，手动设置的方式
     *
     * @param registry
     */
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        // 解决静态资源无法访问
        registry.addResourceHandler("/**").addResourceLocations("classpath:/static/");
        // 解决swagger无法访问
        registry.addResourceHandler("/swagger-ui.html").addResourceLocations("classpath:/META-INF/resources/");
        // 解决swagger的js文件无法访问
        registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/");
    }
}