Issue with XML formatting when using XmlNode.getChildElements()

Question

Step - 1: Create xml structure

Xmlstreamwriter xmlW = new Xmlstreamwriter();
xmlW.writeStartDocument('utf-8','1.0');
//Salesinvoices
xmlW.writeStartElement(null,'SalesInvoices', null);
xmlw.writeDefaultNamespace('urn:xmlns:http://www.soapservice.com:salesinvoices');
xmlw.writeAttribute('xmlns','','xsi','http://www.w3.org/2001/XMLSchema-instance');
//SalesInvoice
xmlW.writeStartElement(null,'SalesInvoice',null);
//Reference
xmlW.writeStartElement(null,'Reference',null);
xmlW.writeCharacters('xx-112345');
xmlW.writeEndElement();//Reference
//Reference1
xmlW.writeStartElement(null,'Reference1',null);
xmlW.writeCharacters('xx-112345');
xmlW.writeEndElement();//Reference1
xmlW.writeEndElement();//SalesInvoice
xmlW.writeEndElement();//Salesinvoices
xmlW.writeEndDocument();
Dom.document doc1 = new dom.document();
doc1.load(xmlw.getXmlString());
dom.xmlnode xml1 = doc1.getrootelement();
system.debug(doc1.toxmlstring());

Step -2 : pass this xml to a method which creates parent xml nodes with sessionid and header before passing to web service

String str = '<sessionId></sessionId>';
Dom.document doc = new dom.document();
doc.load(str);
dom.xmlnode xml = doc.getrootelement();

for(DOM.XmlNode anyNode: xml1.getChildElements()){
    Dom.XmlNode anyElementNode = xml.addChildElement(anyNode.getName(), anyNode.getNamespace(), '');
}
system.debug(doc.toxmlstring());

Issue: inside the for loop to get child elements, it is detecting only main child of the incoming xml which is "SalesInvoice" and final output is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<sessionId>
    <SalesInvoice xmlns="urn:xmlns:http://www.soapservice.com:salesinvoices" />
</sessionId>

while it is expected to be as follows:

<?xml version="1.0" encoding="UTF-8"?>
<sessionId>
    <SalesInvoices xmlns="urn:xmlns:http://www.soapservice.com:salesinvoices" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
        <SalesInvoice>
            <Reference>xx-112345</Reference>
            <Reference1>xx-112345</Reference1>
        </SalesInvoice>
    </SalesInvoices>
</sessionId>

I tried the following but still output is same:

String str = '<sessionId></sessionId>';
Dom.document doc = new dom.document();
doc.load(str);
dom.xmlnode xml = doc.getrootelement();
Dom.XmlNode anyElementNode = listN(xml, xml1);

public Dom.xmlnode listN(DOM.XmlNode resultnode, dom.xmlnode parentNode){
    resultnode.addChildElement(parentNode.getName(), parentNode.getNamespace(), '');
    if(parentNode.getchildelements() != null && parentNode.getchildelements().size() > 0) {
        for(Dom.xmlnode y : parentNode.getchildelements()) {
            if(y.getchildelements() != null && y.getchildelements().size() > 0) {
                listN(parentNode, y);
            }             
        }
    }
    return resultnode;
}

Answer 1

You will need to keep walking down the children of the Dom.XmlNode records to copy out the inner nodes.

// ... Your first block of code that builds up xm1 from Step 1

String str = '<sessionId></sessionId>';
Dom.document doc = new dom.document();
doc.load(str);
dom.xmlnode xml = doc.getrootelement();

for(DOM.XmlNode anyNode : xml1.getChildElements()){
    Dom.XmlNode anyElementNode = xml.addChildElement(anyNode.getName(), anyNode.getNamespace(), '');
    for (Dom.XmlNode child : anyNode.getChildren()) {
        Dom.XmlNode innerChildNode = anyElementNode.addChildElement(child.getName(), child.getNamespace(), '');
        for (Dom.XmlNode child1 : child.getChildren()) {
            // Assuming the XMLNodeType is TEXT here.
            // Should really recursively check the NodeType at each level
            string body = child1.getText();
            Dom.XmlNode childTextNode = innerChildNode.addTextNode(body);
        }

    }


}
system.debug(doc.toxmlstring());

In practice you wouldn't clone XML nodes like this. Instead use a recursive method that checks the Dom.XmlNodeType using getNodeType().