How to avoid NumberFormatException in Spring boot API

Question

I have a Spring boot Get API which returns a 'User' object for a given user id.

@GetMapping( path = "/users/{userId}")
public ResponseEntity<User> getUser(
        @PathVariable( userId )
                Long id) throws CustomException {
      //retuen user object
}

When someone passes a string value to the endpoint as userId this returns 'NumberFormatException'. Which gives an idea of the type of userId that is used on the side of the system. Is there a possibility that I can return a CustomException rather than returning a 'NumberFormatException'.

One option is to use type String for userId and then try to convert it to Long inside the method. Other than that, Is there a better way to address this issue with any inbuild finalities of Spring Boot?

Answer 1

Yes you can by creating an exception advice class that can handle the runtime exceptions.

For example to handle the exceptions you must do the following:-

1- Create a custom class to use it as an exception response class.

public class ExceptionResponse {

    private String message;

    public ExceptionResponse(String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

2- create an exception handler class to handle the thrown exceptions and add the exceptions that you want to handle.

@RestControllerAdvice
public class ExceptionCatcher {

    @ExceptionHandler(NumberFormatException.class)
    public ResponseEntity<ExceptionResponse> numberFormatExceptionHandler(NumberFormatException exception) {
        ExceptionResponse response = new ExceptionResponse(exception.getMessage());
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(response);
    }
}

Or you can check this link to get more informations spring-rest-error-handling-example

Answer 2

You need to validate the inputs using @Validated annotations. Please follow below link for more details: https://howtodoinjava.com/spring-rest/request-body-parameter-validation/