overridden handleMethodArgumentNotValid method of ResponseEntityExceptionHandler not called - spring

Question

I am trying to have a custom validator and also an ExceptionHandler for my spring boot rest service and when I added ExceptionHandler, the validation errors are not being sent to the UI. So I tried to override handleMethodArgumentNotValid method and that does not work either. Can someone give some insight into this?
This is how I have configured my validation class in the controller -
package services.rest.controller;
import java.io.IOException;
import javax.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import lombok.extern.slf4j.Slf4j;
import services.rest.model.TestInput;
import services.rest.validator.DataValidator;
#RestController
#RequestMapping("/test")
#Slf4j
public class RestResource {
#Autowired
private DataValidator validator;
#PostMapping("/create")
public String create(#Valid final TestInput input) throws IOException {
log.debug(input.toString());
return "Success";
}
#InitBinder()
public void init(final WebDataBinder binder) {
binder.addValidators(validator);
}
}
This is my ExceptionHandler code -
package services.rest.exceptionhandler;
import java.util.ArrayList;
import java.util.List;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.ObjectError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
#SuppressWarnings({ "unchecked", "rawtypes" })
#ControllerAdvice
public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
#ExceptionHandler(Exception.class)
public final ResponseEntity<Object> handleAllExceptions(final Exception ex, final WebRequest request) {
System.out.println("All exceptions Method getting executed!!!!");
final List<String> details = new ArrayList<>();
details.add(ex.getLocalizedMessage());
return new ResponseEntity("Server Error", HttpStatus.INTERNAL_SERVER_ERROR);
}
#Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(final MethodArgumentNotValidException ex,
final HttpHeaders headers, final HttpStatus status, final WebRequest request) {
System.out.println("Validation Error Method getting executed!!!!");
final List<String> details = new ArrayList<>();
for (final ObjectError error : ex.getBindingResult().getAllErrors()) {
details.add(error.getDefaultMessage());
}
return new ResponseEntity("Validation Error", HttpStatus.BAD_REQUEST);
}
}
Initially did not override "handleMethodArgumentNotValid" method. Now after overriding it too, it does not work

Answer 1

Did you check the stack trace, it can be possible that instead of MethodArgumentNotValid exception, ConstraintViolation exception is getting raised. Spring doen not provide any default handler for that.

Answer 2

I tested your example and seems to work. Would be helpful if you would also post TestInput and DataValidator.
Doesn't work doesn't say precisely what happened, my guess is that you just received a 400 status code. If that is the case it might be just because the validation is trigger before but you did not override ResponseEntity<Object> handleBindException(final BindException ex, final HttpHeaders headers, final HttpStatus status, final WebRequest request)

Answer 3

The following approach worked for me:
import java.util.ArrayList;
import java.util.List;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
#Order(Ordered.HIGHEST_PRECEDENCE)
#ControllerAdvice
public class GlobalExceptionHandler {
#ExceptionHandler(Exception.class)
public ResponseEntity<Object> handleAllExceptions(final Exception ex, final WebRequest request) {
System.out.println("All exceptions Method getting executed!!!!");
final List<String> details = new ArrayList<>();
details.add(ex.getLocalizedMessage());
return new ResponseEntity("Server Error", HttpStatus.INTERNAL_SERVER_ERROR);
}
#ExceptionHandler(MissingServletRequestParameterException.class)
protected ResponseEntity<Object> handleMethodArgumentNotValid(final Exception ex, final WebRequest request) {
System.out.println("Validation Error Method getting executed!!!!");
final List<String> details = new ArrayList<>();
details.add(ex.getLocalizedMessage());
return new ResponseEntity("Validation Error", HttpStatus.BAD_REQUEST);
}
}
Basically what I did was:
Not extending from ResponseEntityExceptionHandler class.
Put the #Order(Ordered.HIGHEST_PRECEDENCE).
Create a handler for the exception MissingServletRequestParameterException.
Hope this help you

Answer 4

Define your exception handler pakcage in #ComponentScan in App class.
#SpringBootApplication
#ComponentScan(basePackages = { "services.rest.exceptionhandler" })
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}