Implementing custom exceptions in Spring Boot

Question

I have a simple spring boot application in which I have alot of tables. I have build their models, repositories, service and controller files. I have also tested all the apis through postman. Now I need to implement custom exception in my models. Since I am at the beginning stage and learning things, I am a little confused as to how can I apply exceptions?

From what I have explored, I need to create three files

ErrorDetails.java
GlobalExceptionHandler.java
ResourceNotFoundException.java

Is this correct? If yes suppose I have added these files in my project . How do I implement these exceptions in my apis? Can anybody help me? Would mean alot. Thanks!

Go through this https://stackoverflow.com/questions/8423700/how-to-create-a-custom-exception-type-in-java, Custom exception can be anything as per you application and if you add custom exception then it'll be ease to show user understandable message on UI, application wise error code etc. so three files you mentioned are can be any thing or you can use the same as per your findings. — Mayur, Jul 16 '20 at 07:46

Ashish Karn · Answer 1 · 2020-07-15T17:36:47.113

Whenever there is a case where resources will be not available then throw ResourceNotFoundException i.e. throw new ResourceNotFoundException("Error message of your choice");

For example in class CustomerTypeRepository within method getCustomerTypebyID instead of below code:

if (a == null) {
  return ResponseEntity.notFound().build();
}

you can write

if (a == null) {
  throw new ResourceNotFoundException("Customer type doesn't exist with the given id: "+Id);
}

and after that @ControllerAdvice GlobalExceptionHandler has already implamented for ResourceNotFoundException handler. So no need to worry about.

score 0 · Answer 2 · answered Jul 15 '20 at 18:14

I believe in declaring checked exception as a contract, so I would do something like this

@Service
public class CustomerCategorizationService {

@Autowired
private CustomerTypeRepository customerTypeRepository;

  // -------------- CustomerType API ----------------------- ///

  public CustomerType saveCustomerType(CustomerType obj) throws ServiceException {

Where ServiceException is custom checked exception defined in application.

public CustomerType saveCustomerType(CustomerType obj) throws ServiceException {
  //Other code
  Long id;
  try {
    id = customerTypeRepository.save(obj);
  }catch(DataAccessException cause) {
    throw new ServiceException(cause.getMessage());
  }
  return id;
}

And in @ControllerAdvice

@ExceptionHandler(ServiceException.class)
public ResponseEntity<?> resourceNotFoundException(ServiceException ex, WebRequest request) {
    ErrorDetails errorDetails = new ErrorDetails(new Date(), ex.getMessage(), 
 request.getDescription(false));
    return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
}

We can go one step further and throw custom exception from Controller class (say ResourceException) which will wrap ServiceException. In that case my @ControllerAdvice needs to only deal with ResourceException

Implementing custom exceptions in Spring Boot

2 Answers2