swagger-ui not working with custom XML ObjectMapper - spring-boot

Question

I'm working on a spring boot app that should have swagger-ui enabled.
When accessing http://localhost:8080/swagger-ui.html there is an error popup:
"Unable to infer base url ..."
Additionaly, http://localhost:8080/v2/api-docs shows:
error on line 1 at column 1: Document is empty
The source-code of this page is a json, but it's requested as Content-Type application/xhtml+xml;charset=UTF-8
The cause of this seems to be my custom Jackson configuration:
#Configuration
public class JacksonConfig {
#Bean
public MappingJackson2XmlHttpMessageConverter mappingJackson2XmlHttpMessageConverter() {
return new MappingJackson2XmlHttpMessageConverter(objectMapper());
}
#Bean
public ObjectMapper objectMapper() {
JacksonXmlModule xmlModule = new JacksonXmlModule();
xmlModule.setDefaultUseWrapper(false);
XmlMapper objectMapper = new XmlMapper(xmlModule);
objectMapper
.registerModule(new ParameterNamesModule())
.registerModule(new Jdk8Module())
.registerModule(new JavaTimeModule());
objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.UPPER_CAMEL_CASE);
objectMapper
.configure(MapperFeature.DEFAULT_VIEW_INCLUSION, false)
.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
return objectMapper;
}
}
With the following dependency:
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
</dependency>
The problem is also described here: https://github.com/springfox/springfox/issues/1835
So my question is: How do I specify the priority of the jackson message converter to get swagger-ui working?

Answer 1

I just stumbled upon the solution while re-reading my own question.
Just add this to the above JacksonConfig class (don't know if ordering is important, but it works).
#Bean
public MappingJackson2HttpMessageConverter jsonConverter() {
MappingJackson2HttpMessageConverter jsonConverter = new MappingJackson2HttpMessageConverter();
ObjectMapper objectMapper = new ObjectMapper();
jsonConverter.setObjectMapper(objectMapper);
return jsonConverter;
}

Answer 2

Inside the swagger code, it checks to see if an ObjectMapper exists, and if not, it creates one to use. If a bean has been created that uses either an ObjectMapper or XMLMapper, then Swagger will use this instance, and get corrupted. The way round this is to create a bean for the ObjectMapper and use the #Primary annotation, then create the XMLMapper bean you want to use.
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
#Configuration
public class MessageResponseXMLMapper {
#Bean
#Primary
public ObjectMapper customObjectMapper() {
return new ObjectMapper();
}
#Bean(name="customXmlMapper")
public XmlMapper customXmlMapper() {
return new Jackson2ObjectMapperBuilder()
.indentOutput(true)
.createXmlMapper(true)
.propertyNamingStrategy(PropertyNamingStrategy.UPPER_CAMEL_CASE)
.build(); }
}
Hope this helps