How to handle 404 error for amazon s3 bucket in my spring boot code

Question

I have actually a problem within my spring-boot application i developed a restful api linked to an s3 bucket i've customized some exceptions but when i run my url to get an object that doesn't exsit in the console i saw this error exception in my console :

2019-07-25 09:06:45.733 ERROR 1 --- [-nio-443-exec-1] oaccC[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is com.amazonaws.services.s3.model.AmazonS3Exception: The specified key does not exist. (Service: Amazon S3; Status Code: 404; Error Code: NoSuchKey; Request ID: 60E24BCF6860FC66; S3 Extended Request ID: DUEnMWN7YZKug74Q15uHt4Zei3+a7SxTNYzoj99O0YW58WOwvkdM1kwYpcHrGJiTrLkRLOdUL5I=), S3 Extended Request ID: DUEnMWN7YPOAIZADg74Q15uHt4Zei3+a7SxTNYzoj99O0YW58WOwvkdM1kwYpcHrGJiTrLkRLOdUL5I=] with root cause

com.amazonaws.services.s3.model.AmazonS3Exception: The specified key does not exist. (Service: Amazon S3; Status Code: 404; Error Code: NoSuchKey; Request ID: 60E24BCF6860FC66; S3 Extended Request ID: DUEnMWN7YZKug74Q15uHt4ZDFSFSQSDei3+a7SxTNYzoj99O0YW58WOwvkdM1kwYpcHrGJiTrLkRLOdUL5I=)

So my question is how to perform customization to this error in 2 points:

1. Not having this error showing in the console (technically I don't mean change log parameters)
2. Handle this exception with some methods

Answer 1

Write custom exception handler to capture your exceptions and do graceful things.

@ControllerAdvice
@RestController
public class CustomExceptionHandler extends ResponseEntityExceptionHandler {

    @ExceptionHandler(AmazonS3Exception.class)
    public final ResponseEntity<Object> handleAmazonS3Exception(AmazonS3Exception ex, WebRequest request) {
        ApiError apiError = new ApiError(UNPROCESSABLE_ENTITY, ex.getLocalizedMessage(), ex.getErrors());
        return new ResponseEntity<>(apiError, UNPROCESSABLE_ENTITY);
    }
}

Here, UNPROCESSABLE_ENTITY is a HttpStatus ( org.springframework.http.HttpStatus )

Please change the code of method handleAmazonS3Exception(...) based on your requirement.

Answer 2

If you want to avoid the exception completely, you can use the Aws s3 api to see if the object exists or not before trying to download it. I think the method is doesObjectExist . But seems like overkill if you anyway are going to download the file in case it exists. So you can put a try-catch and if you end up catching AmazonS3Exception then check the status code and do stuff accordingly.