How to show Exception name in Spring Boot's JSON Response - spring-boot

Question

I have a Spring Controller which may throw a Runtime Exception at a certain point:
#RequestMapping("/list")
public List<User> findAll() {
// if here
throw new RuntimeException("Some Exception Occured");
}
When I request that URI, the JSON does not include the Exception name ("Runtime Exception"):
curl -s http://localhost:8080/list
{
"timestamp": "2020-04-01T13:15:11.091+0000",
"status": 500,
"error": "Internal Server Error",
"message": "Some Exception Occured",
"path": "/list"
}
Is there way to have it included in the JSON which is returned?
Thanks!

Answer 1

I think you can do that by extending the DefaultErrorAttributes and provide a custom list of attributes to be displayed in the returned JSON. For example, the following one provides a custom error response for Field errors:
import org.springframework.boot.web.servlet.error.DefaultErrorAttributes;
import org.springframework.context.MessageSource;
import org.springframework.validation.FieldError;
import org.springframework.validation.ObjectError;
import org.springframework.web.context.request.WebRequest;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
public class ResolvedErrorAttributes extends DefaultErrorAttributes {
private MessageSource messageSource;
public ResolvedErrorAttributes(MessageSource messageSource) {
this.messageSource = messageSource;
}
#Override
public Map<String, Object> getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {
Map<String, Object> errorAttributes = super.getErrorAttributes(webRequest, includeStackTrace);
resolveBindingErrors(errorAttributes);
return errorAttributes;
}
private void resolveBindingErrors(Map<String, Object> errorAttributes) {
List<ObjectError> errors = (List<ObjectError>) errorAttributes.get("errors");
if (errors == null) {
return;
}
List<String> errorMessages = new ArrayList<>();
for (ObjectError error : errors) {
String resolved = messageSource.getMessage(error, Locale.US);
if (error instanceof FieldError) {
FieldError fieldError = (FieldError) error;
errorMessages.add(fieldError.getField() + " " + resolved + " but value was " + fieldError.getRejectedValue());
} else {
errorMessages.add(resolved);
}
}
errorAttributes.put("errors", errorMessages);
}
}
In this tutorial you can find some more details about Spring Boot custom error responses.