Propogate errors to UI with Spring 3 MVC / REST - rest

Question

When /api/upload REST endpoint is accessed I have a UploadController that uses a service UploadService to upload a file to an ftp server with org.apache.commons.net.ftp.FTPClient. I would like to be able to send information back to the user if the ftp client was unable to connect or timed out, or successfully sent the file. I have some IOException handling, but I don't know how to turn that around and send it back to the front-end. Any help appreciated, thanks!
public void upload(InputStream inputStream) {
String filename = "file.txt"
client = new FTPClient();
try {
client.connect("ftpsite");
client.login("username", "password");
client.storeFile(filename, inputStream);
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
try {
if (inputStream!= null) {
inputStream.close();
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
return null;
}

Answer 1

You should throw a new Exception in your catch statement.
For example, you could create a RequestTimeoutException class:
#ResponseStatus(HttpStatus.REQUEST_TIMEOUT)
public class RequestTimeoutException extends RuntimeException { }
and then throw it when need be:
catch (IOException ioe) {
//do some logging while you're at it
throw new RequestTimeoutException();
}