Would it be possible to complete the javadoc of the class MtomUtil?
Besides, some functions should be changed.
In particular in #extractAttachmentRootElement.
This method searches an element called "attachments" and assumes all the attachments are located below.
This is not explained in the java doc.
And this might be the behavior in the Talend SE and in the FileTransfer BC, but in the Jsr-181, it does not work this way. Other components might work differently too.
The method #extractAttachmentsIdFromPayload is useful.
But there could be another one more useful: the one that gets all the mappings at once.
I will attach an implementation then. Could you add it in the implementation (if you judge it a useful addition)? 
Very good idea Vincent.
I will add your implementation.
Thank you.