Is it good practice to throw exception from DAO layer to controller?

Question

I am writing one REST api. There might be two exceptions in my DAO layer namely Exception_X and Exception_Y. If I encountered a exception Exception_X in DAO layer, my controller should return status code 200, if Exception_Y then 401 and if all goes well controller should return 201. Now what was I thinking that I will throw encountered exception as it is from DAO layer to controller via service layer and in catch block of controller I will return response. Is it acceptable or there is some other standard way?

Answer 1

Yes that is quite an acceptable way. However, rather than using try-catch, I would suggest to implement Exception Handlers for your REST Controllers. That way, you won't have to clutter your REST methods.

Also, it would be better to create a model object in REST layer for Error messages - ErrorResponse, with appropriate information:

class ErrorResponse {
    int statusCode;
    String errorMessage;
}

And return it's object from the exception handlers. BTW, you can also map your exception class directly to a response using @ResponseStatus annotation:

@ResponseStatus(value=401, reason="message")
class Exception_Y extends RuntimeException {
} 

Then you don't have to write exception handler for that exception.