Currently swagger has the limitation that just the error code is returned and not the modelled error object - at least for the Java client, so you are not able to get the error details via this method. Luckily you can grab the raw response as well via apiException.getResponseBody().toString()
:
// for the correct usage please consult the most recent examples
try {
} catch (ApiException e) {
// currently just a string is returned!
String jsonString = e.getResponseBody().toString();
// potentially parse the json and read hints
throw new RuntimeException(jsonString);
}