Writing a good interface to de-couple from a particular technology … what to do about exceptions?

manpreet Best Answer 2 years ago

I want to write a Java interface to de-couple from a particular technology , what's the best way of forwarding exceptions. Let's say that the technology I want to de-couple from is Amazon SQS. Amazon SQS is essentially a queue service and I want to be as flexible as possible and I want to have the option of easily substituting SQS with RabbitMQ or other queue service.

Here's what I have so far :

public interface QueueService {

   // URL of the Queue Server
   public void setURL(String url); 
   public String getURL();

   public Msg getMessage() throws QueueServiceException;
   public void deleteMessage(String messageId) throws QueueServiceException;

}

The SQS implementation of getMessage is probably fairly easy, it just uses the Amazon AWS Java SDK and essentially the receiveMessage method of the AmazonSQS class. Here is the signature of this method in the AWS Java SDK:

  public ReceiveMessageResult receiveMessage(ReceiveMessageRequest receiveMessageRequest)  throws AmazonServiceException, AmazonClientException;

Now my question is what do I do with these exceptions in an implementation of the QueueService interface... do I just catch these exceptions ( which are specific to a particular technology ) and re-throw as QueueServiceException ?

try {
  messages = amazonSQS.receiveMessage(receiveMessageRequest).getMessages()
} catch(AmazonServiceException ase) {
      throw new QueueServiceException();
}

QueueServiceException is :

public class QueueServiceException extends Exception {

    public QueueServiceException (String message){
        super(message);
    }

    public QueueServiceException(String message, Throwable cause){
        super(message, cause);

    }

}

Any thoughts ?

Cheers !