Can I retrieve the original SBD Paypload?

[Kinchkun]

Cheers,

thank you for your work :)

I am developing a PEPPOL Access Point (AP) which stores retrieved documents in Amazon S3. For this, I am implementing the following interface:

fun handleIncomingSBD(
    @Nonnull aMessageMetadata: IAS4IncomingMessageMetadata,
    @Nonnull aHeaders: HttpHeaderMap,
    @Nonnull aUserMessage: Ebms3UserMessage,
    @Nonnull aSBDBytes: ByteArray,
    @Nonnull aSBD: StandardBusinessDocument,
    @Nonnull aPeppolSBD: PeppolSBDHData,
    @Nonnull aState: IAS4MessageState,
    @Nonnull aProcessingErrorMessages: ICommonsList<Ebms3Error>,
) {
    val payloadBytes = serializeElement(aSBD.any as Element)
    s3.storeBytes(payloadBytes)
}

I only want the payload and not the SBD itself.

What I don't like about this solution is that we retrieve the SBD bytes, parse it into an XML tree, and then serialize part of the tree back into bytes.

Is there a way to access the original payload bytes? The serialization and deserialization process slightly alters the original message, not in a meaningful way, but I need to store the byte-wise exact original message somehow.

Kind regards,

[phax]

@Kinchkun thanks for starting that dicussion. I understand your request, but it cannot be fulfilled generically because of the following reason:

• SBDH includes the payload elements as an xs:any
• This means, that the transmission that you receive is a single XML document
• As such, the the general rules for XML namespaces apply, as described in https://www.w3.org/TR/xml-names/
• Therefore it is possible, that the namespace URL of the (e.g.) Invoice element is contained inside the surrounding StandardBusinessDocument element as in this example:

<StandardBusinessDocument xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns="http://www.unece.org/cefact/namespaces/StandardBusinessDocumentHeader"
  xmlns:ubl="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2">
  <StandardBusinessDocumentHeader>
    <!-- etc. -->
  </StandardBusinessDocumentHeader>
  <ubl:Invoice>
    <!-- etc. -->
  </ubl:Invoice>
</StandardBusinessDocument>

==> Therefore, if you "extract" the payload from the SBDH you would receive an invalid XML document because the ubl namespace prefix would be undefined.

So you should be aware, that XML is NOT a text format, but an application format (that's why the preferred MIME type is application/xml) and it is safe to read the payload and re-serialize it, because the content is "semantically equivalent", even though the serialization is different. The key element for equality of XML is the equality in memory, and not in serialized form.

[Kinchkun]

Hi,
thank you for your fast and thoroughly response. Now I understand the issue, thank you.