Issue in rendering Swagger OpenAPI v3 UI + Springboot project - swagger

Question

I am getting the error -
"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)."
when I paste the generated json from /api-docs to editor.swagger.io.
I have some observations.
localhost:8080/v3/api-docs/ yields -
"{\"openapi\":\"3.0.1\", "\info\":{ ----------------
This json gives the mentioned error in editor.swagger.io.
On manually removing the initial double quotes and escape character i.e.
{"openapi":"3.0.1", "info":{ ---------------- the error goes away i.e. UI is rendered without any issue.
My project springboot version is 2.2.13.RELEASE, springdoc-openapi-ui version is 1.5.8, jackson-databind version is 2.10.5.1
OpenAPI config class -
#Configuration
public class Config1 {
#Bean
public GroupedOpenApi publicApi() {
return GroupedOpenApi.builder()
.group("user")
.pathsToMatch("/v1/**")
.build();
}
#Bean
public OpenAPI customOpenAPI() {
return new OpenAPI()
.info(new Info().title("title1").description("test").version("1.0.0"));
}
Please let me know if any further information is required from my end. Any inputs regarding the issue will be helpful. Thank you.

Answer 1

I had the same issue with spring-boot-2.6.4, springdoc-openapi-1.6.6.
The problem is localhost:8080/v3/api-docs/ responses "{"openapi":"3.0.1", "\info":{..." which is a String, NOT a valid JSON as expected.
It turns out in my WebMvcConfig implements WebMvcConfigurer, it doesn't have a StringHttpMessageConverter, so the solution is to add it to converters:
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(stringHttpMessageConverter());
...
}
#Bean
public StringHttpMessageConverter stringHttpMessageConverter() {
StringHttpMessageConverter messageConverter = new StringHttpMessageConverter();
messageConverter.setSupportedMediaTypes(List.of(MediaType.APPLICATION_JSON, MediaType.TEXT_PLAIN, MediaType.ALL));
return messageConverter;
}
If you're extending WebMvcConfigurationSupport instead of implementing WebMvcConfigurer, probably you'll not get this error as the StringHttpMessageConverter is added by default.

Answer 2

You can use .version("v0.0.1") in your customOpenAPI or publicApi like this
#Bean
public OpenAPI springShopOpenAPI() {
return new OpenAPI()
.version("v0.0.1"));
}
For more details see docs https://springdoc.org/#migrating-from-springfox