public Credentials unmarshall(StaxUnmarshallerContext context) throws Exception {
    Credentials credentials = new Credentials();
    int originalDepth = context.getCurrentDepth();
    int targetDepth = originalDepth + 1;

    if (context.isStartOfDocument()) targetDepth += 2;

    while (true) {
      XMLEvent xmlEvent = context.nextEvent();
      if (xmlEvent.isEndDocument()) return credentials;

      if (xmlEvent.isAttribute() || xmlEvent.isStartElement()) {
        if (context.testExpression("AccessKeyId", targetDepth)) {
          credentials.setAccessKeyId(StringStaxUnmarshaller.getInstance().unmarshall(context));
          continue;
        }
        if (context.testExpression("SecretAccessKey", targetDepth)) {
          credentials.setSecretAccessKey(StringStaxUnmarshaller.getInstance().unmarshall(context));
          continue;
        }
        if (context.testExpression("SessionToken", targetDepth)) {
          credentials.setSessionToken(StringStaxUnmarshaller.getInstance().unmarshall(context));
          continue;
        }
        if (context.testExpression("Expiration", targetDepth)) {
          credentials.setExpiration(DateStaxUnmarshaller.getInstance().unmarshall(context));
          continue;
        }
      } else if (xmlEvent.isEndElement()) {
        if (context.getCurrentDepth() < originalDepth) {
          return credentials;
        }
      }
    }
  }