How to handle exceptions thrown in the service layer? - spring-boot

Question

I'm working on a spring-boot application. I tried handling exceptions .But i guess there is something wrong about how I'm doing it because it always throws internal server error 500.
I tried setting up custom exception classes and also used response status codes with #ResponseStatus. But regardless of what the exception is it throws an internal server error only.
I'm using intellij and the message i've given in the exception is printed there but the response body is empty.This i guess must be because it is throwing an internal server error.
Controller class
#RequestMapping(value = "/attendance",method = RequestMethod.POST)
public ResponseEntity<?> enterAttendance(#RequestBody ViewDTO viewDTO) throws CustomException{
return new ResponseEntity<>(tempResultServices.handleAttendance(viewDTO),HttpStatus.OK);
}
}
Service layer
#Override
public TempResult handleAttendance(ViewDTO viewDTO) throws CustomException {
TempIdentity tempIdentity=new TempIdentity();
tempIdentity.setRegistrationNo(viewDTO.getRegistrationNo());
tempIdentity.setCourseId(viewDTO.getCourseId());
tempIdentity.setYear(viewDTO.getYear());
tempIdentity.setSemester(viewDTO.getSemester());
User user=userService.findByUserId(viewDTO.getUserId());
tempIdentity.setUser(user);
if(!viewDTO.isAttendance()){
TempResult tempResultUser =new TempResult(tempIdentity,viewDTO.isAttendance(),0);
ResultIdentity resultIdentity=new ResultIdentity(tempIdentity.getRegistrationNo(),tempIdentity.getCourseId(),tempIdentity.getYear(),tempIdentity.getSemester());
Result result=new Result(resultIdentity,0,"E*");
AttendanceDraft attendanceDraft=atteDraftService.findDraft(viewDTO.getRegistrationNo(),viewDTO.getCourseId(),viewDTO.getYear(),viewDTO.getSemester(),viewDTO.getUserId());
if(attendanceDraft!=null){
attendanceDraft.setStatus(true);
atteDraftService.save(attendanceDraft);
//atteDraftService.delete(attendanceDraft);
tempResultRepository.save(tempResultUser);
resultRepository.save(result);
return tempResultUser;
}
else{
throw new CustomException("No draft available");
}
}
else{
TempResult tempResultUser =new TempResult(tempIdentity,viewDTO.isAttendance());
AttendanceDraft attendanceDraft=atteDraftService.findDraft(viewDTO.getRegistrationNo(),viewDTO.getCourseId(),viewDTO.getYear(),viewDTO.getSemester(),viewDTO.getUserId());
if(attendanceDraft!=null){
attendanceDraft.setStatus(true);
atteDraftService.save(attendanceDraft);
//atteDraftService.delete(attendanceDraft);
tempResultRepository.save(tempResultUser);
return tempResultUser;
}
else{
throw new CustomException("No draft available");
}
}
}
The exception class
#ResponseStatus(code= HttpStatus.NOT_FOUND)
public class CustomException extends RuntimeException {
public CustomException(String message){
super(message);
}
}
The terminal in the intellij prints "No draft available ". But i want it not as an internal server error.
Can some one tell me how i should be handling these errors please?
I tried using the #RestControllerAdvice
#RestControllerAdvice
public class WebRestControllerAdvice {
#ExceptionHandler(CustomException.class)
public ResponseMsg handleNotFoundException(CustomException ex) {
ResponseMsg responseMsg = new ResponseMsg(ex.getMessage());
return responseMsg;
}
}
And this is my response message class
public class ResponseMsg {
private String message;
//getters and setters
}
This is another simple request in the application
#RequestMapping(value = "/user/view",method = RequestMethod.POST)
public ResponseEntity<?> getUser(#RequestBody UserDTO userDTO) throws CustomException{
User user=userService.findByUsername(userDTO.getUsername());
if(user!=null){
return ResponseEntity.ok(user);
}
//
throw new CustomException("User not found");
}
But still the custom exception is not thrown. The response body is empty. but intellij says "user not found" and postman returns the status code 500.

Answer 1

Spring boot has a very convenient way to handle exceptions in any layer of your application which is defining a #ControllerAdvice bean. Then you can throw any type of exception in your code and it will be "captured" on this class.
After this you can handle and return whatever your app needs to return.
By the way, you can return your custom object and it will be parsed to json automatically.
Documentation: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/
Sample code:
#ControllerAdvice
public class ErrorHandler {
#ExceptionHandler(BadRequestException.class)
#ResponseStatus(HttpStatus.BAD_REQUEST)
#ResponseBody
public Object processValidationError(BadRequestException ex) {
//return whatever you need to return in your API
}
}