Parse strings in any XML format

You cannot convert an arbitrary XML string directly into a %XML.Adaptor object without a class definition that represents the XML structure. The available material shows that %XML.Reader works together with %XML.Adaptor, but you must first define a class that extends %XML.Adaptor and matches the XML structure, then correlate the XML root or element to that class and read it. [1][2]

A typical pattern is:

Class MyApp.Messages.PatientXML Extends (%Persistent, %XML.Adaptor)
{
Parameter XMLNAME = "Patient";

Property PatientID As %String;
Property PatientName As %String;
Property Age As %String;
Property DateOfBirth As %String;
Property Sex As %String;
Property PatientClass As %String;
Property AssignedPatientLocation As %String;
Property AttendingDoctor As %String;

ClassMethod XMLToObject(xmlStream As %Stream.Object = "", xmlString, filename = "C:\learn\hl7msg\test.xml")
{
    Set reader = ##class(%XML.Reader).%New() 

    If filename'="" {
        Set sc=reader.OpenFile(filename)
    }
    ElseIf $IsObject(xmlStream){
        Set sc=reader.OpenStream(xmlStream)
    }
    ElseIf xmlString'="" {
        Set sc=reader.OpenString(xmlString)
    }
    Else {
        Return $$$ERROR("No file name,string or stream found")
    }

    If $$$ISERR(sc) Do $system.OBJ.DisplayError(sc) Quit

    Do reader.CorrelateRoot($classname())
    Do reader.Next(.patient,.sc) 
    If $$$ISERR(sc) Do $system.OBJ.DisplayError(sc) Quit

    ZWrite patient
}
}

[1]

The more general import flow is:

1. Create a %XML.Reader instance.
2. Open the XML from a file, stream, or string.
3. Associate an XML element with a class by using Correlate() or CorrelateRoot().
4. Call Next() to instantiate and populate the object. [1][2]

Example:

Set reader = ##class(%XML.Reader).%New()
Set sc = reader.OpenString(xml)
Do reader.Correlate("resultado","EsquemasDatos.Radiologia.Resultado")
Do reader.Next(.ReturnObject,.sc)

This returns an object of the correlated class. [3][4]

If your goal is specifically to handle any XML dynamically without creating a predefined class, the suitable option shown is EnsLib.EDI.XML.Document, not %XML.Adaptor. It allows runtime and XPath-based access to XML content without requiring a predefined schema or class. [1]

Example:

ClassMethod ParseXML(xmlfile As %String="")
{
    Set ediXMLDoc = ##class(EnsLib.EDI.XML.Document).ImportFromFile(xmlfile,,.sc)
    If $$$ISERR(sc) {
      Quit
    }
    Write ediXMLDoc.GetValueAt("/Patient/PatiendID")
}

[1]

So the answer is:

• If you want a %XML.Adaptor object, you need a matching class definition. [1][2]
• If you do not want to create classes and need to parse arbitrary XML, use EnsLib.EDI.XML.Document for dynamic access instead. [1]

Sources: