File Template Iterator Example for File Writer in Channel Destination

[mp3pete]

I'm trying to create a simple custom xml output file based on an incoming HL7 feed. In the file template I need to iterate through multiple nested xml tags. Below is an example with multiple patients.

I'd like to avoid using XSL if possible. Is there a way to use Javascript here or does it have to happen in the transformer? Either way could you provide an example?

<?xml version="1.0" encoding="UTF-8" ?>
<patients>
<!-- iterate through each patient -->
<patient>
<accountNumber>${Account Number}</accountNumber>
<patientNumber>${Patient Number}</patientNumber>
<firstName>${First Name}</firstName>
<lastName>${Last Name}</lastName>
<middleName>${Middle Name}</middleName>
<birthDate>${DOB}</birthDate>
</patient>
<patients>