Spring #RestController produces XML without namespaces - spring

Question

I have a #RestController which should return a result from a SOAP web service. The web service client classes are generated with maven-jaxb2-plugin and therefore using JAXB annotations.
#RestController
public class ZemisPersonSearchController {
#Autowired(required = true)
private SoapClient soapClient;
#RequestMapping(path = "/api/persons/{no}", produces = { MediaType.APPLICATION_JSON_UTF8_VALUE, MediaType.APPLICATION_XML_VALUE })
#PreAuthorize("hasRole('ROLE_GET_PERSON_DETAILS')")
public ResponseEntity<Object> getPersonDetails(HttpServletRequest httpReq, #PathVariable String no) {
Result result = soapClient.getPersonDetails(UUID.randomUUID().toString(), no);
return new ResponseEntity<>(result, HttpStatus.OK);
}
}
#XmlAccessorType(XmlAccessType.FIELD)
#XmlType(name = "", propOrder = {
"responseHeader",
"getPersonDetailsResponse",
"searchPersonResponse",
"systemException"
})
#XmlRootElement(name = "result")
public class Result {
#XmlElement(name = "ResponseHeader")
protected ResponseHeaderType responseHeader;
#XmlElement(name = "GetPersonDetailsResponse")
protected PersonType getPersonDetailsResponse;
#XmlElement(name = "SearchPersonResponse")
protected SearchPersonResponseType searchPersonResponse;
#XmlElement(name = "SystemException")
protected FaultInfoType systemException;
...
As long as all works as expected, the result looks like:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:result
xmlns:ns2="http://mynamespace/personsearchservice/v1">
<ns2:ResponseHeader>
...
But if there goes something wrong (i.e. soap endpoint isn't available) and an excpetion is thrown, the REST controller returns an 406 http status since the automatically generated response cannot be transformed to XML.
I've tried to extend my application with Jackson XML and registered the module to process JAXB annotations as suggested in documentations and blogs I found.
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-jaxb-annotations</artifactId>
</dependency>
#Bean
public Module jaxbModule() {
return new JaxbAnnotationModule();
}
But if I do so, the error for exceptions can now be generated as XML and I got the correct http status 500, but also the response when no error occurs contains no longer namespaces and it is important to keep the namespaces since it is a big and complex xml:
<result>
<ResponseHeader>
Does anybody have an idea what I have to do to get either the namespaces with jackson or the error transformed to xml with JAXB?

Answer 1

I found out, that spring creates a LinkedHashMap with error details automatically. When this map should be converted to html without jackson-xml on classpath, the http status 406 is given back due to a missing converter for the LinkedHashMap to html. So my solution is to add a simple AbstractHttpMessageConverter to my application which converts the map with error details to html. Therefore I don't need jackson-xml on the classpath and my XML is generated from JAXB with namespaces included.
The converter:
public class HttpXmlExceptionConverter extends AbstractHttpMessageConverter<Map<String, Object>> {
public HttpXmlExceptionConverter() {
super(MediaType.APPLICATION_XML, MediaType.TEXT_XML, new MediaType("application", "*+xml"));
}
#Override
protected boolean supports(Class<?> clazz) {
return Map.class.isAssignableFrom(clazz);
}
#Override
protected Map readInternal(Class<? extends Map<String, Object>> clazz, HttpInputMessage inputMessage)
throws IOException, HttpMessageNotReadableException {
throw new NotImplementedException("readFromSource is not supported!");
}
#Override
protected void writeInternal(Map<String, Object> map, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
OutputStream s = outputMessage.getBody();
StringBuilder sb = new StringBuilder();
sb.append("<map>");
for (Entry<String, Object> entry : map.entrySet()) {
sb.append("<").append(entry.getKey()).append(">");
if (entry.getValue() != null)
sb.append(StringEscapeUtils.escapeXml(entry.getValue().toString()));
sb.append("</").append(entry.getKey()).append(">");
}
sb.append("</map>");
s.write(sb.toString().getBytes(Charset.defaultCharset()));
}
}
And register the converter:
#Configuration
//#EnableWebMvc
// -> EnableWebMvc is required if you don't want the spring boot auto configuration should be extended
public class WebMvcConfig implements WebMvcConfigurer {
#Override
public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(new HttpXmlExceptionConverter());
}
}