private String getRequestIdFromHeaders(Map<String, String> headers) {
        for (Entry<String, String> headerEntry : headers.entrySet()) {
            if (headerEntry.getKey().equalsIgnoreCase(X_AMZN_REQUEST_ID_HEADER)) {
                return headerEntry.getValue();
            }
            if (headerEntry.getKey().equalsIgnoreCase(X_AMZ_REQUEST_ID_ALTERNATIVE_HEADER)) {
                return headerEntry.getValue();
            }
        }
        return null;
    }
Create an AmazonServiceException using the chain of unmarshallers. This method will never
return null, it will always return a valid AmazonServiceException

@param errorCode
           Error code to find an appropriate unmarshaller
@param response
           The HTTP response
@param jsonNode
           JsonNode of HTTP response
@param rawContent
           The raw bytes of the HTTP response content
@return AmazonServiceException
aws-java-sdk-core/src/main/java/com/amazonaws/http/JsonErrorResponseHandler.java