Incoming JMS message

Folks

I am new to JMS Adapter and have a scenario which sounds difficult

I have a Mesage arriving in JMS queue which will be a collection of invoices , again to be posted onto IDOCS in ECC

Is the Queue message format XML, usually or does it come as a file ?

The structure of the message will be such that few of the nodes will be present if it comes from one source and will not be present when it comes from the others,

Is there a standard way to differentiate on the basis of the incoming message, in JMS adapter functionality or a code has to be written ?

Do i need to be a Core Java coder to use JMS adapter ??

please help