Apex class to XML Format is not as expected about apex-for-xero

[sarava77]

I want allocate the created Credit Notes to invoice

<Allocations>
 <Allocation>
   <AppliedAmount>60.50</AppliedAmount>
   <Invoice>
     <InvoiceID>f5832195-5cd3-4660-ad3f-b73d9c64f263</InvoiceID>
   </Invoice>
 </Allocation>
</Allocations>

So I have created the class below structure

public class JSON2Apex {

public Allocation Allocation=new Allocation();

public class Allocation {
public String AppliedAmount;
public Invoice Invoice=new Invoice();
}

public class Invoice {
public String InvoiceID;
}

}

This is the code I am executing in Salesforce developer console

String consumerKey;
HttpResponse response;
Xero_Settings__c xeroSettings=Xero_Settings__c.getInstance('UKINC');
consumerKey = xeroSettings.Consumer_Key__c;
JSON2Apex js=new JSON2Apex ();
JSON2Apex.Allocation alt=new JSON2Apex.Allocation();
alt.AppliedAmount='1.0';
alt.Invoice.InvoiceID='test';
js.Allocation=alt;String xmlInvoiceString = XeroXmlUtility.serialize(js, 'Allocations');
System.debug('*****************'+xmlInvoiceString);

And the Output structure is coming like below

<?xml version="1.0" encoding="UTF-8"?>
<Allocations>
  <Allocation>
     <AppliedAmount>1.0</AppliedAmount>
  </Allocation>
  <Invoice>
     <InvoiceID>test</InvoiceID>
  </Invoice>
</Allocations>

This Structure is not as expected there is some issue , Can any one know how to fix this.

[danielbprobert]

i'm doing something similar but using

have you public class for allocation like this:

public class Allocation {
public String AppliedAmount;
public XeroInvoice Invoice;
}