XML Processing

Content:

  1. Introduction
  2. Examples
  3. W3C DOM
  4. Alternate DOM's
  5. Streaming push parser
  6. Streaming pull parser
  7. XML binding
  8. Streaming write
  9. Serialization
  10. XPath
  11. XSLT transformation

Introduction:

XML (eXtensible Markup Language) is a standard for markup languages created by W3C.

It is a sub set of SGML (Standard Generalized Markup Language).

It is widely used for all sort sof data and data description.

Most modern programming languages and runtimes have good support for XML.

Examples:

In the following sections we will see various techniques to read, update and write XML using various programming languages and XML libraries.

The examples will use the following super simple XML file.

employees.xml:

<?xml version='1.0' standalone='yes'?>
<employees>
    <employee no='1'>
        <name>Alan A</name>
        <role>Manager</role>
    </employee>
    <employee no='2'>
        <name>Brian B</name>
        <role>Engineer</role>
    </employee>
    <employee no='3'>
        <name>Chris C</name>
        <role>Sales rep</role>
    </employee>
</employees>

The C examples will be shown in simple - possible a bit oldfashioned - C. I will expect examples to work with C 89 compliant compilers.

Windows GCC build:

gcc -m32 -Wall -Wno-pointer-sign -I%ICONVPATH%\include -I%LIBXML2PATH%\include\libxml2 -I%LIBXSLTPATH%\include %1.c -L%LIBXML2PATH%\lib -lxml2 -L%ICONVPATH%\lib -liconv -L%ZLIBPATH%\lib -lz -L%LIBXSLTPATH%\lib -lxslt -o %1.exe

W3C DOM:

W3C DOM is a W3C standard for an in memory tree structure reprsenting XML.

Pro's:

Con's:

package xmlproc;

import java.io.File;
import java.io.FileWriter;
import java.io.Writer;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.bootstrap.DOMImplementationRegistry;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSSerializer;

public class W3CDOM {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document doc = db.parse(new File(XML_FILE));
        // iterate over all employee elements
        NodeList employees = doc.getElementsByTagName("employee");
        for (int i = 0; i < employees.getLength(); i++) {
            Element employee = (Element)employees.item(i);
            // find attribute no
            String no = employee.getAttribute("no");
            // find sub elements name and role 
            String name = "";
            String role = "";
            NodeList children = employee.getChildNodes();
            for (int j = 0; j < children.getLength(); j++) {
                Node child = children.item(j);
                if(child.getNodeType() == Node.ELEMENT_NODE) {
                    if (child.getNodeName().equals("name")) {
                        name = child.getFirstChild().getNodeValue();
                    }
                    if (child.getNodeName().equals("role")) {
                        role = child.getFirstChild().getNodeValue();
                    }
                }
            }
            // print
            System.out.println("no=" + no);
            System.out.println("name=" + name);
            System.out.println("role=" + role);
        }
        // add employee
        Element newname = doc.createElement("name");
        newname.appendChild(doc.createTextNode("Dave D"));
        Element newrole = doc.createElement("role");
        newrole.appendChild(doc.createTextNode("Intern"));
        Element newemployee = doc.createElement("employee");
        newemployee.setAttribute("no", "4");
        newemployee.appendChild(newname);
        newemployee.appendChild(newrole);
        doc.getDocumentElement().appendChild(newemployee);
        // write out
        DOMImplementation impl = DOMImplementationRegistry.newInstance().getDOMImplementation("XML 3.0");
        DOMImplementationLS feature = (DOMImplementationLS)impl.getFeature("LS","3.0");
        LSSerializer ser = feature.createLSSerializer();
        ser.getDomConfig().setParameter("format-pretty-print", true);
        LSOutput output = feature.createLSOutput();
        Writer w = new FileWriter("/work/employees2.xml");
        output.setCharacterStream(w);
        ser.write(doc, output);
        w.close();
    }
}

Finding sub elements is a bit cumbersome (it can be done easier using XPath - see below). And the write out API really looks like design by committee.

Note that it uses the socalled abstract factory pattern. This allows one to change the implementation used.

How to:


System.setProperty("javax.xml.parsers.DocumentBuilderFactory", "com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl"); // use default (copy of Apache Xerces)
System.setProperty("javax.xml.parsers.DocumentBuilderFactory", "org.apache.xerces.jaxp.DocumentBuilderFactoryImpl"); // use Apache Xerces
System.setProperty("javax.xml.parsers.DocumentBuilderFactory", "org.apache.crimson.jaxp.DocumentBuilderFactoryImpl"); // use old Crimson
using System;
using System.IO;
using System.Xml;

namespace XmlProc.W3CDOM
{
    public class Program
    {
        private const String XML_FILE = @"C:\work\employees.xml";
        public static void Main(string[] args)
        {
            // read from file to DOM tree
            XmlDocument doc = new XmlDocument();
            doc.Load(XML_FILE);
            // iterate over all employee elements
            foreach(XmlElement employee in doc.DocumentElement.GetElementsByTagName("employee"))
            {
                // find attribute no
                string no = employee.Attributes["no"].Value;
                // find sub elements name and role
                string name = "";
                string role = "";
                foreach(XmlNode child in employee.ChildNodes)
                {
                    if(child.NodeType == XmlNodeType.Element && child.Name == "name")
                    {
                        name = child.FirstChild.Value;    
                    }
                    if(child.NodeType == XmlNodeType.Element && child.Name == "role")
                    {
                        role = child.FirstChild.Value;    
                    }
                }
                // print
                Console.WriteLine("no = " + no);
                Console.WriteLine("name = " + name);
                Console.WriteLine("role = " + role);
            }
            // add employee
            XmlElement newname = doc.CreateElement("name");
            newname.AppendChild(doc.CreateTextNode("Dave D"));
            XmlElement newrole = doc.CreateElement("role");
            newrole.AppendChild(doc.CreateTextNode("Intern"));
            XmlElement newemployee = doc.CreateElement("employee");
            XmlAttribute newno = doc.CreateAttribute("no");
            newno.Value = "4";
            newemployee.Attributes.Append(newno);
            newemployee.AppendChild(newname);
            newemployee.AppendChild(newrole);
            doc.DocumentElement.AppendChild(newemployee);
            // write out
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                doc.Save(sw);
            }
            Console.ReadKey();
        }
    }
}

Finding sub elements is a bit cumbersome (it can be done easier using XPath - see below).

Imports System
Imports System.IO
Imports System.Xml

Namespace XmlProc.W3CDOM
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Public Shared Sub Main(args As String())
            ' read from file to DOM tree
            Dim doc As New XmlDocument()
            doc.Load(XML_FILE)
            ' iterate over all employee elements
            For Each employee As XmlElement In doc.DocumentElement.GetElementsByTagName("employee")
                ' find attribute no
                Dim no As String = employee.Attributes("no").Value
                ' find sub elements name and role
                Dim name As String = ""
                Dim role As String = ""
                For Each child As XmlNode In employee.ChildNodes
                    If child.NodeType = XmlNodeType.Element AndAlso child.Name = "name" Then
                        name = child.FirstChild.Value
                    End If
                    If child.NodeType = XmlNodeType.Element AndAlso child.Name = "role" Then
                        role = child.FirstChild.Value
                    End If
                Next
                ' print
                Console.WriteLine("no = " & no)
                Console.WriteLine("name = " & name)
                Console.WriteLine("role = " & role)
            Next
            ' add employee
            Dim newname As XmlElement = doc.CreateElement("name")
            newname.AppendChild(doc.CreateTextNode("Dave D"))
            Dim newrole As XmlElement = doc.CreateElement("role")
            newrole.AppendChild(doc.CreateTextNode("Intern"))
            Dim newemployee As XmlElement = doc.CreateElement("employee")
            Dim newno As XmlAttribute = doc.CreateAttribute("no")
            newno.Value = "4"
            newemployee.Attributes.Append(newno)
            newemployee.AppendChild(newname)
            newemployee.AppendChild(newrole)
            doc.DocumentElement.AppendChild(newemployee)
            ' write out
            Using sw As New StreamWriter("C:\work\employees2.xml")
                doc.Save(sw)
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace

Finding sub elements is a bit cumbersome (it can be done easier using XPath - see below).

<html>
<head>
<title>W3C DOM</title>
</head>
<body>
<h1>W3C DOM</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// read from file to DOM tree
$doc = new DOMDocument();
$doc->load(XML_FILE);
// iterate over all employee elements
$employees = $doc->getElementsByTagName('employee');
foreach($employees as $employee) {
    // find attribute no
    $no = $employee->attributes->getNamedItem('no')->nodeValue;
    // find sub elements name and role
    $name = '';
    $role = '';
    foreach($employee->childNodes as $child) {
        if($child->nodeType == XML_ELEMENT_NODE) {
            if($child->nodeName == 'name') {
                $name = $child->firstChild->nodeValue;
            }
            if($child->nodeName == 'role') {
                $role = $child->firstChild->nodeValue;
            }
        }
    }
    // print
    echo "<tr>\r\n";
    echo "<td>$no</td>\r\n";
    echo "<td>$name</td>\r\n";
    echo "<td>$role</td>\r\n";
    echo "</tr>\r\n";
}
echo "</table>\r\n";
// add employee
$newname = $doc->createElement('name');
$newname->appendChild($doc->createTextNode('Dave D'));
$role = $doc->createElement('role');
$role->appendChild($doc->createTextNode('Intern'));
$newemployee = $doc->createElement('employee');
$newemployee->setAttribute('no', '4');
$newemployee->appendChild($newname);
$newemployee->appendChild($role);
$doc->documentElement->appendChild($newemployee);
// write out
echo "<pre>\r\n";
echo str_replace(array('<','>'),array('&lt;','&gt;'),$doc->saveXML());
echo "<pre>\r\n";
?>
</body>
</html>

Finding sub elements is a bit cumbersome (it can be done easier using XPath - see below).

<html>
<head>
<title>W3C DOM</title>
</head>
<body>
<h1>W3C DOM</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<%
NODE_ELEMENT = 1
' read from file to DOM tree
Set doc = CreateObject("MSXML.DOMDocument")
doc.Async = False
doc.Load("C:\work\employees.xml")
' iterate over all employee elements
Set employees = doc.GetElementsByTagName("employee")
For Each employee in employees
    ' find attribute no
    no = employee.Attributes.GetNamedItem("no").Value
    ' find sub elements name and role
    For Each child in employee.ChildNodes
        If(child.nodeType = NODE_ELEMENT And child.NodeName = "name") Then
            name = child.FirstChild.NodeValue
        End If
        If(child.nodeType = NODE_ELEMENT And child.NodeName = "role") Then
            role = child.FirstChild.NodeValue
        End If
    Next
    ' print
    Response.Write "<tr>" & vbCrLf
    Response.Write "<td>" & no & "</td>" & vbCrLf
    Response.Write "<td>" & name & "</td>" & vbCrLf
    Response.Write "<td>" & role & "</td>" & vbCrLf
    Response.Write "</tr>" & vbCrLf
Next
Response.Write  "</table>" & vbCrLf
' add employee
Set name = doc.CreateElement("name")
name.AppendChild(doc.CreateTextNode("Dave D"))
Set role = doc.CreateElement("role")
role.AppendChild(doc.CreateTextNode("Intern"))
Set newemployee = doc.CreateElement("employee")
Call newemployee.SetAttribute("no", "4")
newemployee.AppendChild(name)
newemployee.AppendChild(role)
doc.DocumentElement.AppendChild(newemployee)
' write out
Response.Write "<pre>" & vbCrLf
Response.Write Replace(Replace(doc.XML, "<", "&lt;"), ">", "&gt;")
Response.Write "</pre>" & vbCrLf
' cleanup
Set employees = Nothing
Set name = Nothing
Set role = Nothing
Set newemployee = Nothing
Set doc = Nothing
%>
</body>
</html>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/parser.h>
#include <libxml/tree.h>

#define XML_FILE "employees.xml"

int main()
{
    xmlDoc *doc;
    xmlNode *root;
    xmlNode *employee;
    xmlNode *element;
    xmlChar *no;
    xmlChar *name;
    xmlChar *role;
    /* read from file to DOM tree */
    doc = xmlReadFile(XML_FILE, NULL, 0);
    if (doc == NULL)
    {
        fprintf(stderr, "Failed to parse %s\n", XML_FILE);
        return EXIT_FAILURE;
    }
    /* iterate over all elements below root (employee elements) */
    root = xmlDocGetRootElement(doc);
    employee = root->children;
    do
    {
        if(!xmlIsBlankNode(employee))
        {
            /* find attribute no */
            no = xmlGetProp(employee, "no");
            /* find sub elements name and role */
            element = employee->children;
            do
            {
                if(!xmlIsBlankNode(element))
                {
                    if(strcmp(element->name, "name") == 0)
                    {
                        name = element->children->content;
                    }
                    if(strcmp(element->name, "role") == 0)
                    {
                        role = element->children->content;
                    }
                }
                element = element->next;
            }
            while(element != NULL);
            /* print */
            printf("no=%s\n", no);
            printf("name=%s\n", name);
            printf("role=%s\n", role);
        }
        employee = employee->next;
    }
    while(employee != NULL);
    /* add employee */
    employee = xmlNewNode(NULL, "employee");
    xmlNewProp(employee, "no", "4");
    element = xmlNewNode(NULL, "name");
    xmlAddChild(element, xmlNewText("Dave D"));
    xmlAddChild(employee, element);
    element = xmlNewNode(NULL, "role");
    xmlAddChild(element, xmlNewText("Intern"));
    xmlAddChild(employee, element);
    xmlAddChild(root, employee);
    /* write out */
    xmlDocDump(stdout, doc);
    /* clean up */
    xmlFreeDoc(doc);
    xmlCleanupParser();
    /* */
    return EXIT_SUCCESS;
}
#include <iostream>
#include <cstdlib>

using namespace std;

#include <xercesc/dom/DOM.hpp>
#include <xercesc/framework/XMLFormatter.hpp>
#include <xercesc/framework/LocalFileFormatTarget.hpp>
#include <xercesc/parsers/XercesDOMParser.hpp>
#include <xercesc/sax/HandlerBase.hpp>
#include <xercesc/util/PlatformUtils.hpp>
#include <xercesc/util/XMLString.hpp>

using namespace xercesc;

const char *XML_FILE = "employees.xml";

// hackish utility functions - do not use in production
static XMLCh buf[10][1000];
static int bufix = -1;

static XMLCh *UTF16(const char *s)
{
    bufix = (bufix + 1) % 10;
    XMLString::transcode(s, buf[bufix], sizeof(buf[bufix]) - 1);
    return buf[bufix];
}

static char *UTF8(const XMLCh *s)
{
    return XMLString::transcode(s);
}

int main()
{
    try
    {
        XMLPlatformUtils::Initialize();
        // read from file to DOM tree
        XercesDOMParser *parser = new XercesDOMParser();
        parser->setErrorHandler((ErrorHandler*) new HandlerBase());
        parser->parse(XML_FILE);
        DOMDocument *doc = parser->getDocument();
        // iterate over all employee elements
        DOMNodeList *employees = doc->getElementsByTagName(UTF16("employee"));
        for(int i = 0; i < employees->getLength(); i++) 
        {
            DOMElement *employee = (DOMElement *)employees->item(i);
            // find attribute no
            int no = atoi(UTF8(employee->getAttribute(UTF16("no"))));
            // find sub elements name and role 
            DOMNodeList *children = employee->getChildNodes();
            char *name = NULL;
            char *role = NULL;
            for(int j = 0; j < children->getLength(); j++) {
                DOMNode *child = children->item(j);
                if(child->getNodeType() == DOMNode::NodeType::ELEMENT_NODE)
                {
                    if(strcmp(UTF8(child->getNodeName()), "name") == 0)
                    {
                        name = UTF8(child->getFirstChild()->getNodeValue());
                    }
                    if(strcmp(UTF8(child->getNodeName()), "role") == 0)
                    {
                        role = UTF8(child->getFirstChild()->getNodeValue());
                    }
                }
            }
            // print
            cout << "no = " << no << endl;
            cout << "name = " << name << endl;
            cout << "role = " << role << endl;
        }
        // add employee
        DOMElement *newname = doc->createElement(UTF16("name"));
        newname->appendChild(doc->createTextNode(UTF16("Dave D")));
        DOMElement *newrole = doc->createElement(UTF16("role"));
        newrole->appendChild(doc->createTextNode(UTF16("Intern")));
        DOMElement *newemployee = doc->createElement(UTF16("employee"));
        newemployee->setAttribute(UTF16("no"), UTF16("4"));
        newemployee->appendChild(newname);
        newemployee->appendChild(newrole);
        doc->getDocumentElement()->appendChild(newemployee);
        // write out
        DOMImplementation *impl = DOMImplementationRegistry::getDOMImplementation(UTF16("LS"));
        DOMLSSerializer *ser = ((DOMImplementationLS *)impl)->createLSSerializer();
        ser->getDomConfig()->setParameter(XMLUni::fgDOMWRTFormatPrettyPrint, true);
        DOMLSOutput *output = ((DOMImplementationLS*)impl)->createLSOutput();
        XMLFormatTarget *ft = new LocalFileFormatTarget(UTF16("employees2.xml"));
        output->setByteStream(ft);
        ser->write(doc, output);
        output->release();
        //
        doc->release();
        XMLPlatformUtils::Terminate();
    }
    catch (const XMLException &ex)
    {
        cout << UTF8(ex.getMessage()) << endl;
        exit(1);
    }
    catch (const DOMException &ex)
    {
        cout << UTF8(ex.getMessage()) << endl;
        exit(1);
    }
    catch (...)
    {
        cout << "Ooops" << endl;
        exit(1);
    }
    return 0;
}
program W3CDOM;

uses
   Classes, DOM, XMLRead, XMLWrite;

const
  XML_FILE = 'employees.xml';

var
   parser : TDOMParser;
   doc : TXMLDocument;
   employees, children : TDOMNodeList;
   employee, child : TDOMNode;
   newname, newrole, newemployee : TDOMElement;
   no, name, role : WideString;
   i, j : integer;

begin
  (* read from file to DOM tree *)
  parser := TDOMparser.Create;
  parser.Parse(TXMLInputSource.Create(TFileStream.Create(XML_FILE, fmOpenRead)), doc);
  parser.Free;
  (* iterate over all employee elements *)
  employees := doc.GetElementsByTagName('employee');
  for i := 0 to employees.Count - 1 do begin
    employee := employees.Item[i];
    (* find attribute no *)
    no := employee.Attributes.GetNamedItem('no').NodeValue;
    (* find sub elements name and role  *)
    name := '';
    role := '';
    children := employee.ChildNodes;
    for j := 0 to children.Count - 1 do begin
      child :=  children.Item[j];
      if child.NodeType = ELEMENT_NODE then begin
        if child.NodeName = 'name' then begin
           name := child.FirstChild.NodeValue;
        end;
        if child.NodeName = 'role' then begin
           role := child.FirstChild.NodeValue;
        end;
      end;
    end;
    (* print *)
    writeln('no=', no);
    writeln('name=', name);
    writeln('role=', role);
  end;
  (* add employee *)
  newname := doc.CreateElement('name');
  newname.AppendChild(doc.CreateTextNode('Dave D'));
  newrole := doc.CreateElement('role');
  newrole.AppendChild(doc.CreateTextNode('Intern'));
  newemployee := doc.CreateElement('employee');
  newemployee.SetAttribute('no', '4');
  newemployee.AppendChild(newname);
  newemployee.AppendChild(newrole);
  doc.DocumentElement.AppendChild(newemployee);
  (* write out *)
  WriteXMLFile(doc, 'employees2.xml');
  (* *)
  doc.Free;
end.
from xml.dom.minidom import parse
from xml.dom import Node

XML_FILE = '/work/employees.xml'

# read from file to DOM tree
doc = parse(XML_FILE)
# iterate over all employee elements
employees = doc.getElementsByTagName('employee')
for employee in employees:
    # find attribute no
    no = employee.getAttribute('no')
    # find sub elements name and role
    name = ''
    role = ''
    children = employee.childNodes
    for child in children:
        if child.nodeType == Node.ELEMENT_NODE:
            if child.nodeName == 'name':
                name = child.firstChild.nodeValue
            if child.nodeName == 'role':
                role = child.firstChild.nodeValue
    # print
    print('no = %s' % no)
    print('name = %s' % name)
    print('role = %s' % role)
# add employee
newname = doc.createElement('name')
newname.appendChild(doc.createTextNode('Dave D'))
newrole = doc.createElement('role')
newrole.appendChild(doc.createTextNode('Intern'))
newemployee = doc.createElement('employee')
newemployee.setAttribute('no', '4')
newemployee.appendChild(newname)
newemployee.appendChild(newrole)
doc.documentElement.appendChild(newemployee)
# write out
doc.writexml(open('/work/employees2.xml', 'w'), '', '    ', '\n')

Alternate DOM's:

Due to W3C DOM being a bit verbose/cumbersome then some alternative DOM's aka in memory tree representations have been created.

Pro's:

Con's:

package xmlproc;

import java.io.FileWriter;
import java.io.Writer;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

public class JDOM2 {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        SAXBuilder b = new SAXBuilder();
        Document doc = b.build(XML_FILE);
        // iterate over all employee elements
        for(Element employee : doc.getRootElement().getChildren()) {
            // find attribute no
            String no = employee.getAttributeValue("no");
            // find sub elements name and role
            String name = employee.getChild("name").getText();
            String role = employee.getChild("role").getText();
            // print
            System.out.println("no=" + no);
            System.out.println("name=" + name);
            System.out.println("role=" + role);
        }
        // add employee
        Element newname = new Element("name");
        newname.setText("Dave D");
        Element newrole = new Element("role");
        newrole.setText("Intern");
        Element newemployee = new Element("employee");
        newemployee.setAttribute("no", "4");
        newemployee.addContent(newname);
        newemployee.addContent(newrole);
        doc.getRootElement().addContent(newemployee);
        // write out
        XMLOutputter fmt = new XMLOutputter(Format.getPrettyFormat());
        Writer w = new FileWriter("/work/employees2.xml");
        w.write(fmt.outputString(doc));
        w.close();
    }
}

Much easier than W3C DOM.

package xmlproc;

import java.io.FileOutputStream;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

public class DOM4J {
    private final static String XML_FILE = "/work/employees.xml";
    @SuppressWarnings("unchecked")
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        SAXReader xmlReader = new SAXReader();
        Document doc = xmlReader.read(XML_FILE);
        // iterate over all employee elements
        for(Element employee : (List<Element>)doc.getRootElement().elements("employee")) {
            // find attribute no
            String no = employee.attributeValue("no");
            // find sub elements name and role
            String name = employee.elementText("name");
            String role = employee.elementText("role");
            // print
            System.out.println("no=" + no);
            System.out.println("name=" + name);
            System.out.println("role=" + role);
        }
        // add employee
        Element newemployee = doc.getRootElement().addElement("employee");
        newemployee.addAttribute("no", "4");
        newemployee.addElement("name").addText("Dave D");
        newemployee.addElement("role").addText("Intern");
        // write out
        OutputFormat of = OutputFormat.createPrettyPrint();
        FileOutputStream fos = new FileOutputStream("/work/employees2.xml");
        XMLWriter xw = new XMLWriter(fos, of);
        xw.write(doc);
        xw.close();
        fos.close();
    }
}

Much easier than W3C DOM.

using System;
using System.IO;
using System.Xml.Linq;

namespace XmlProc.AltDOM
{
    public class Program
    {
        private const String XML_FILE = @"C:\work\employees.xml";
        public static void Main(string[] args)
        {
            // read from file to DOM tree
            XDocument doc = XDocument.Load(XML_FILE);
            // iterate over all employee elements
            foreach(XElement employee in doc.Root.Elements("employee"))
            {
                // find attribute no
                string no = employee.Attribute("no").Value;
                string name = employee.Element("name").Value;
                string role = employee.Element("role").Value;
                Console.WriteLine("no = " + no);
                Console.WriteLine("name = " + name);
                Console.WriteLine("role = " + role);
            }
            // add employee
            XElement newname = new XElement("name");
            newname.Value = "Dave D";
            XElement newrole = new XElement("role");
            newrole.Value = "Intern";
            XElement newemployee = new XElement("employee", new XAttribute("no", "4"));
            newemployee.Add(newname);
            newemployee.Add(newrole);
            doc.Root.Add(newemployee);
            // write out
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                doc.Save(sw);
            }
            Console.ReadKey();
        }
    }
}

Easier than W3C DOM.

Imports System
Imports System.IO
Imports System.Xml.Linq

Namespace XmlProc.AltDOM
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Public Shared Sub Main(args As String())
            ' read from file to DOM tree
            Dim doc As XDocument = XDocument.Load(XML_FILE)
            ' iterate over all employee elements
            For Each employee As XElement In doc.Root.Elements("employee")
                ' find attribute no
                Dim no As String = employee.Attribute("no").Value
                Dim name As String = employee.Element("name").Value
                Dim role As String = employee.Element("role").Value
                Console.WriteLine("no = " & no)
                Console.WriteLine("name = " & name)
                Console.WriteLine("role = " & role)
            Next
            ' add employee
            Dim newname As New XElement("name")
            newname.Value = "Dave D"
            Dim newrole As New XElement("role")
            newrole.Value = "Intern"
            Dim newemployee As New XElement("employee", New XAttribute("no", "4"))
            newemployee.Add(newname)
            newemployee.Add(newrole)
            doc.Root.Add(newemployee)
            ' write out
            Using sw As New StreamWriter("C:\work\employees2.xml")
                doc.Save(sw)
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace

Easier than W3C DOM.

PHP also has a XML parser that parse XML into a pseudo DOM tree. It utilize PHP dynamic typing to generate a real object structure with named properties instead of the DOM generic nodes with string values. This result in a very easy to use interface.

<html>
<head>
<title>SimpleXML</title>
</head>
<body>
<h1>SimpleXML</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// read from file to pseudo DOM tree
$xml = new SimpleXMLElement(file_get_contents(XML_FILE));
// iterate over all employee elements
foreach($xml->employee as $employee) {
    // find attribute no
    $no = $employee['no'];
    // find sub elements name and role
    $name = $employee->name;
    $role = $employee->role;
    // print
    echo "<tr>\r\n";
    echo "<td>$no</td>\r\n";
    echo "<td>$name</td>\r\n";
    echo "<td>$role</td>\r\n";
    echo "</tr>\r\n";
}
?>
</table>
</body>
</html>

Easier than W3C DOM.

SimpleXML is much more used than DOM in PHP.

Note that it is possible to update an SimpleXML object structure, but I do not consider that a natural usage of SimpleXML.

Also note that XML namespaces and SimpleXML is known to cause problems.

Python has an ElementTree API for more convenient access to XML.

from xml.etree import ElementTree

XML_FILE = '/work/employees.xml'

# read from file to DOM tree
doc = ElementTree.parse(XML_FILE)
# iterate over all employee elements
for employee in doc.getroot().iter('employee'):
    # find attribute no
    no = employee.get('no')
    # find sub elements name and role
    name = employee.find('name').text
    role = employee.find('role').text
    # print
    print('no = %s' % no)
    print('name = %s' % name)
    print('role = %s' % role)
# add employee
newemployee = ElementTree.SubElement(doc.getroot(), 'employee')
newemployee.set('no', '4')
newname = ElementTree.SubElement(newemployee, 'name')
newname.text = 'Dave D'
newrole = ElementTree.SubElement(newemployee, 'role')
newrole.text = 'Intern'
# write out
doc.write('/work/employees2.xml')

Streaming push parser:

A streaming push parser reads XML and perform callbacks whenever it encounters something.

The only widely used parser of this type is the Java SAX parser. And therefore it is often simply referred to as a SAX parser.

Pro's:

Con's:

package xmlproc;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

public class ParseSAX {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // process file with MySaxParser as event handler
        SAXParserFactory spf = SAXParserFactory.newInstance();
        SAXParser sp = spf.newSAXParser();
        XMLReader xr = sp.getXMLReader();
        xr.setContentHandler(new MySaxParser());
        xr.parse(XML_FILE);
    }
}

class MySaxParser extends DefaultHandler {
    private StringBuilder sb = new StringBuilder();
    // accumulate text (note: can be called multiple times for a text node)
    public void characters(char buf[], int offset, int len) throws SAXException {
        sb.append(new String(buf, offset, len));
    }
    // process start element
    public void startElement(String namespaceURI, String localName, String rawName, Attributes atts) throws SAXException {
        // if employee element find no and print
        if (rawName.equals("employee")) {
            String no = atts.getValue("no");
            System.out.println("no=" + no);
        }
        // if sub elements name or role start accumulating
        if (rawName.equals("name") || rawName.equals("role")) {
            sb = new StringBuilder();   
        }
    }
    // process end element
    public void endElement(String namespaceURI, String localName, String rawName) throws SAXException {
        // if sub elements name or role stop accumulating and print
        if (rawName.equals("name")) {
            String name = sb.toString();
            System.out.println("name=" + name);
        }
        if (rawName.equals("role")) {
            String role = sb.toString();
            System.out.println("role=" + role);
        }
    }
}

This example is not so bad, but try imagine how the code would be with a deeeply nested XML structure.

<html>
<head>
<title>Push parser</title>
</head>
<body>
<h1>Push parser</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// process file with specified event handlers
$parser = xml_parser_create();
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);  // default is to uppercase everything !!
xml_set_element_handler($parser, 'startElement', 'endElement');
xml_set_character_data_handler($parser, 'characters');
xml_parse($parser, file_get_contents(XML_FILE));
xml_parser_free($parser);

$accdata = '';

// accumulate text (note: can be called multiple times for a text node)
function characters($parser, $data) {
    global $accdata;
    $accdata .= $data;  
}

// process start element, if 'employee' find attribute no
function startElement($parser, $name, $atts) {
    global $accdata;
    // if employee element find no and print
    if($name == 'employee') {
        $no = $atts['no'];
        echo "<tr>\r\n";
        echo "<td>$no</td>\r\n";
    }
    // if sub elements name or role start accumulating
    if($name == 'name' || $name == 'role') {
        $accdata = '';
    }
}

// process end element
function endElement($parser, $name) {
    global $accdata;
    // if sub elements name or role stop accumulating and print
    if($name == 'name') {
        $name = $accdata;
        echo "<td>$name</td>\r\n";
    }
    if($name == 'role') {
        $role = $accdata;
        echo "<td>$role</td>\r\n";
    }
    if($name == 'employee') {
        echo "</tr>\r\n";
    }
}

?>
</table>
</body>
</html>

This example is not so bad, but try imagine how the code would be with a deeeply nested XML structure.

And the usage of global is really bad as well.

I have never seen this XML parser being used in PHP.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/parser.h>

#define XML_FILE "employees.xml"

struct state
{
    int len;
    char *buf;
};

/* accumulate text (note: can be called multiple times for a text node) */
void onCharacters(struct state *state, const xmlChar *ch,   int len)
{
    memcpy(state->buf + state->len, ch, len);
    state->len += len;
}

/* process start element */
void onStartElement(struct state *state, const xmlChar *name, const xmlChar **attrs)
{
    /* if employee element find no and print */
    if(strcmp(name, "employee") == 0)
    {
        printf("no=%s\n", attrs[1]); // [0] is first attribute name, [1] is first attribute value
    }
    /* if sub elements name or role start accumulating */
    if(strcmp(name, "name") == 0 || strcmp(name, "role") == 0)
    {
        state->len = 0;
    }
}

/* process end element */
void onEndElement(struct state *state, const xmlChar *name)
{
    /* if sub elements name or role stop accumulating and print */
    if(strcmp(name, "name") == 0)
    {
        state->buf[state->len] = 0;
        printf("name=%s\n", state->buf);
    }
    if(strcmp(name, "role") == 0)
    {
        state->buf[state->len] = 0;
        printf("role=%s\n", state->buf);
    }
}

int main()
{
    xmlSAXHandler *myhandler;
    struct state mystate;
    // process file with specified event handlers
    myhandler = malloc(sizeof(xmlSAXHandler));
    memset(myhandler, 0, sizeof(xmlSAXHandler));
    myhandler->characters = (charactersSAXFunc)onCharacters;
    myhandler->startElement = (startElementSAXFunc)onStartElement;
    myhandler->endElement = (endElementSAXFunc)onEndElement;
    mystate.len = 0;
    mystate.buf = malloc(10000);
    xmlSAXUserParseFile(myhandler, &mystate, XML_FILE);
    /* */
    return EXIT_SUCCESS;
}
#include <iostream>
#include <cstdlib>

using namespace std;

#include <xercesc/parsers/SAXParser.hpp>
#include <xercesc/sax/HandlerBase.hpp>
#include <xercesc/util/PlatformUtils.hpp>
#include <xercesc/util/XMLString.hpp>

using namespace xercesc;

const char *XML_FILE = "employees.xml";

// hackish utility functions - do not use in production
static XMLCh buf[10][1000];
static int bufix = -1;

static XMLCh *UTF16(const char *s)
{
    bufix = (bufix + 1) % 10;
    XMLString::transcode(s, buf[bufix], sizeof(buf[bufix]) - 1);
    return buf[bufix];
}

static char *UTF8(const XMLCh *s)
{
    return XMLString::transcode(s);
}

class MySaxParser : public HandlerBase
{
    private:
        XMLCh buf[10000]; // hardcoded size - do not use in production
        int buflen;
    public:
        void characters (const XMLCh *const chars, const XMLSize_t length);
        void startElement(const XMLCh *const name, AttributeList& attributes);
        void endElement(const XMLCh *const name);
};

// accumulate text (note: can be called multiple times for a text node)
void MySaxParser::characters(const XMLCh *const chars, const XMLSize_t length)
{
    memcpy(buf + buflen, chars, length * sizeof(XMLCh));
    buflen += length * sizeof(XMLCh);
}

// process start element
void MySaxParser::startElement(const XMLCh *const name, AttributeList& atts)
{
    // if employee element find no and print
    if(strcmp(UTF8(name), "employee") == 0)
    {
        int no = atoi(UTF8(atts.getValue(UTF16("no"))));
        cout << "no = " << no << endl;
        
    }
    // if sub elements name or role start accumulating
    if(strcmp(UTF8(name), "name") == 0 || strcmp(UTF8(name), "role") == 0)
    {
        buflen = 0;
    }
}

// process end element
void MySaxParser::endElement(const XMLCh *const name)
{
    // if sub elements name or role stop accumulating and print
    if(strcmp(UTF8(name), "name") == 0)
    {
        memset(buf + buflen, 0, sizeof(XMLCh));
        char *name = UTF8(buf);
        cout << "name = " << name << endl;
    }
    if(strcmp(UTF8(name), "role") == 0)
    {
        memset(buf + buflen, 0, sizeof(XMLCh));
        char *role = UTF8(buf);
        cout << "role = " << role << endl;
    }
}

int main()
{
    try
    {
        XMLPlatformUtils::Initialize();
        // process file with MySaxParser as event handler
        SAXParser *parser = new SAXParser();
        parser->setDocumentHandler(new MySaxParser());
        parser->parse(XML_FILE);
        //
        XMLPlatformUtils::Terminate();
    }
    catch (const XMLException &ex)
    {
        cout << UTF8(ex.getMessage()) << endl;
        exit(1);
    }
    catch (const SAXParseException &ex)
    {
        cout << UTF8(ex.getMessage()) << endl;
        exit(1);
    }
    catch (...)
    {
        cout << "Ooops" << endl;
        exit(1);
    }
    return 0;
}
from xml.sax import make_parser
from xml.sax.handler import ContentHandler

class MySaxParser(ContentHandler):
    def __init__(self):
        self.sb = ''
    # accumulate text (note: can be called multiple times for a text node)
    def characters(self, content):
        self.sb = self.sb + content
    # process start element
    def startElement(self, rawname, attrs):
        # if employee element find no and print
        if rawname == 'employee':
            no = attrs['no']
            print('no = %s' % no)
        # if sub elements name or role start accumulating
        if (rawname == 'name') or (rawname == 'role'):
            self.sb = ''
    # process end element
    def endElement(self,  rawname):
        # if sub elements name or role stop accumulating and print
        if rawname == 'name':
            name = self.sb
            print('name = %s' % name)
        if rawname == 'role':
            role = self.sb
            print('role = %s' % role)

XML_FILE = '/work/employees.xml'

# process file with MySaxParser as event handler
parser = make_parser()
parser.setContentHandler(MySaxParser())
parser.parse(XML_FILE)

Streaming pull parser:

A streaming pull parser reads XML using a traditional get/read API.

Pro's:

Con's:

package xmlproc;

import java.io.FileInputStream;
import java.io.InputStream;

import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamReader;

public class ParseStAX {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // open file
        XMLInputFactory xif = XMLInputFactory.newInstance();
        InputStream is = new FileInputStream(XML_FILE);
        XMLStreamReader xsr = xif.createXMLStreamReader(is);
        // process file
        StringBuilder sb = new StringBuilder();
        while(xsr.hasNext()) {
            xsr.next();
            switch(xsr.getEventType()) {
                // accumulate text (note: can be entered multiple times for a text node)
                case XMLStreamReader.CHARACTERS:
                    sb.append(xsr.getText());
                    break;
                case XMLStreamReader.START_ELEMENT:
                    // if employee element find no and print
                    if (xsr.getLocalName().equals("employee")) {
                        String no = xsr.getAttributeValue(null, "no");
                        System.out.println("no=" + no);
                    }
                    // if sub elements name or role start accumulating
                    if (xsr.getLocalName().equals("name") || xsr.getLocalName().equals("role")) {
                        sb = new StringBuilder();   
                    }
                    break;
                case XMLStreamReader.END_ELEMENT:
                    // if sub elements name or role stop accumulating and print
                    if (xsr.getLocalName().equals("name")) {
                        String name = sb.toString();
                        System.out.println("name=" + name);
                    }
                    if (xsr.getLocalName().equals("role")) {
                        String role = sb.toString();
                        System.out.println("role=" + role);
                    }
                    break;
            }
        }
        // close file
        xsr.close();
        is.close();
    }
}
using System;
using System.IO;
using System.Text;
using System.Xml;

namespace XmlProc.Pull
{
    public class Program
    {
        private const String XML_FILE = @"C:\work\employees.xml";
        public static void Main(string[] args)
        {
            // open file
            using(StreamReader sr = new StreamReader(XML_FILE)) 
            {
                XmlReader xr = new XmlTextReader(sr);
                // process file
                StringBuilder sb = new StringBuilder();
                while(xr.Read())
                {
                    switch(xr.NodeType)
                    {
                        // accumulate text
                        case XmlNodeType.Text:
                            sb.Append(xr.Value);
                            break;
                        case XmlNodeType.Element:
                            // if employee element find no and print
                            if (xr.Name == "employee")
                            {
                                String no = xr.GetAttribute("no");
                                Console.WriteLine("no=" + no);
                            }
                            // if sub elements name or role start accumulating
                            if (xr.Name == "name" || xr.Name == "role")
                            {
                                sb = new StringBuilder();   
                            }
                            break;
                        case XmlNodeType.EndElement:
                            // if sub elements name or role stop accumulating and print
                            if (xr.Name == "name")
                            {
                                String name = sb.ToString();
                                Console.WriteLine("name=" + name);
                            }
                            if (xr.Name == "role")
                            {
                                String role = sb.ToString();
                                Console.WriteLine("role=" + role);
                            }
                            break;
                    }
                }
                xr.Close();
            }
            Console.ReadKey();
        }
    }
}
Imports System
Imports System.IO
Imports System.Text
Imports System.Xml

Namespace XmlProc.Pull
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Public Shared Sub Main(args As String())
            ' open file
            Using sr As New StreamReader(XML_FILE)
                Dim xr As XmlReader = New XmlTextReader(sr)
                ' process file
                Dim sb As New StringBuilder()
                While xr.Read()
                    Select Case xr.NodeType
                        ' accumulate text
                        Case XmlNodeType.Text
                            sb.Append(xr.Value)
                            Exit Select
                        Case XmlNodeType.Element
                            ' if employee element find no and print
                            If xr.Name = "employee" Then
                                Dim no As String = xr.GetAttribute("no")
                                Console.WriteLine("no=" & no)
                            End If
                            ' if sub elements name or role start accumulating
                            If xr.Name = "name" OrElse xr.Name = "role" Then
                                sb = New StringBuilder()
                            End If
                            Exit Select
                        Case XmlNodeType.EndElement
                            ' if sub elements name or role stop accumulating and print
                            If xr.Name = "name" Then
                                Dim name As String = sb.ToString()
                                Console.WriteLine("name=" & name)
                            End If
                            If xr.Name = "role" Then
                                Dim role As String = sb.ToString()
                                Console.WriteLine("role=" & role)
                            End If
                            Exit Select
                    End Select
                End While
                xr.Close()
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace
<html>
<head>
<title>Pull parser</title>
</head>
<body>
<h1>Pull parser</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// open file
$rdr = new XMLReader();
$rdr->XML(file_get_contents(XML_FILE));
// process file
$accdata = '';
while($rdr->read()){
    switch ($rdr->nodeType) {
        // accumulate text
        case XMLReader::TEXT:
            $accdata .= $rdr->value;
            break;
        case XMLReader::ELEMENT:
            // if employee element find no and print
            if($rdr->localName == 'employee') {
                $no = $rdr->getAttribute('no');
                echo "<tr>\r\n";
                echo "<td>$no</td>\r\n";
            }
            // if sub elements name or role start accumulating
            if($rdr->localName == 'name' || $rdr->localName == 'role') {
                $accdata = '';
            }
            break;
        case XMLReader::END_ELEMENT:
            // if sub elements name or role stop accumulating and print
            if($rdr->localName == 'name') {
                $name = $accdata;
                echo "<td>$name</td>\r\n";
            }
            if($rdr->localName == 'role') {
                $role = $accdata;
                echo "<td>$role</td>\r\n";
            }
            if($rdr->localName == 'employee') {
                echo "</tr>\r\n";
            }
            break;
    }
}
?>
</table>
</body>
</html>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/xmlreader.h>

#define XML_FILE "employees.xml"

int main()
{
    xmlTextReader *xr;
    char *buf;
    buf = malloc(10000);
    buf[0] = 0;
    xr = xmlNewTextReaderFilename(XML_FILE);
    if(xr != NULL)
    {
        while(xmlTextReaderRead(xr))
        {
            switch(xmlTextReaderNodeType(xr))
            {
                case XML_READER_TYPE_TEXT:
                    /* accumulate text */
                    strcat(buf, xmlTextReaderValue(xr));
                    break;
                case XML_READER_TYPE_ELEMENT:
                    /* if employee element find no and print */
                    if(strcmp(xmlTextReaderLocalName(xr), "employee") == 0)
                    {
                        printf("no=%s\n",xmlTextReaderGetAttribute(xr, "no"));
                    }
                    /* if sub elements name or role start accumulating */
                    if(strcmp(xmlTextReaderLocalName(xr), "name") == 0 || strcmp(xmlTextReaderLocalName(xr), "role") == 0)
                    {
                        buf[0] = 0;
                    }
                    break;
                case XML_READER_TYPE_END_ELEMENT:
                    /* if sub elements name or role stop accumulating and print */
                    if(strcmp(xmlTextReaderLocalName(xr), "name") == 0)
                    {
                        printf("name=%s\n", buf);
                    }
                    if(strcmp(xmlTextReaderLocalName(xr), "role") == 0)
                    {
                        printf("role=%s\n", buf);
                    }
                    break;
            }
        }
        xmlFreeTextReader(xr);
    }
    else
    {
        fprintf(stderr, "Unable to open XML file: %s\n", XML_FILE);
    }
    return EXIT_SUCCESS;
}
program Reader;

uses
  Classes, XmlReader, XmlTextReader, XmlUtils;

const
  XML_FILE = 'employees.xml';

var
  xis : TXMLInputSource;
  xr : TXMLReader;
  buf, no, name, role : WideString;

begin
  (* open file *)
  xis := TXMLInputSource.Create(TFileStream.Create(XML_FILE, fmOpenRead));
  xr := TXMLTextReader.Create(xis, TXMLReaderSettings.Create);
  buf := '';
  while xr.Read do begin
    case xr.nodeType of
      (* accumulate text (note: can be entered multiple times for a text node) *)
      ntText:
        begin
          buf := buf + xr.Value;
        end;
      ntElement:
        begin
          (* if employee element find no and print *)
          if xr.Name = 'employee' then begin
            no := xr.GetAttribute('no');
            writeln('no=', no);
          end;
          (* if sub elements name or role start accumulating *)
          if (xr.Name = 'name') or (xr.Name = 'role') then begin
            buf := '';
          end;
        end;
      ntEndElement:
        begin
          (* if sub elements name or role stop accumulating and print *)
          if xr.Name = 'name' then begin
            name := buf;
            writeln('name=', name);
          end;
          if xr.Name = 'role' then begin
            role := buf;
            writeln('role=', role);
          end;
        end;
    end;
  end;
  (* close file *)
  xr.Free;
  xis.Free;
end.

XML binding:

XML binding takes a completely different approach to reading and writing XML. Instead of doing it manually it maps classes in the programming language to a XML format, so read and write becomes a single operation.

Pro's:

Con's:

package xmlproc;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;

public class Employee {
    private int no;
    private String name;
    private String role;
    public Employee() {
        this(0, null, null);
    }
    public Employee(int no, String name, String role) {
        this.no = no;
        this.name = name;
        this.role = role;
    }
    @XmlAttribute
    public int getNo() {
        return no;
    }
    public void setNo(int no) {
        this.no = no;
    }
    @XmlElement
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @XmlElement
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }
    @Override
    public String toString() {
        return String.format("[%d,%s,%s]", no, name, role);
    }
}

The annotations @XmlAttribute and @XmlElement simply tell whether data is an attribute or an element.

package xmlproc;

import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Employees {
    private List<Employee> list = new ArrayList<>();
    @XmlElements(@XmlElement(name="employee",type=Employee.class))
    public List<Employee> getList(){
        return list;
    }
    public void setList(List<Employee> list) {
        this.list = list;
    }
    @Override
    public String toString() {
        return list.toString();
    }
}

Annotation @XmlRootElement tell that this is the top class. Annotation @XmlElements describes what the list is.

package xmlproc;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;

public class JAXB {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // setup context
        JAXBContext jxbctx = JAXBContext.newInstance(Employees.class);
        // read from file
        Unmarshaller um = jxbctx.createUnmarshaller();
        Employees employees = (Employees)um.unmarshal(new FileInputStream(XML_FILE));
        // add employee
        employees.getList().add(new Employee(4, "Dave D", "Intern"));
        // write out
        Marshaller m = jxbctx.createMarshaller();
        m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        OutputStream os = new FileOutputStream("/work/employees2.xml");
        m.marshal(employees, os);
        os.close();
    }
}

If the XML is documented in an XML schema (XSD file), then one does not need to write the data classes manually. Instead they can be generated from the schema.

Command line:

xjc -d dirwheregeneratedsourceswillbeplaced -p packageforgeneratedclasses nameofschemafile.xsd
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Xml.Serialization;

namespace XmlProc.Binding
{
    public class Employee
    {
        public Employee() : this(0, "", "")
        {
        }
        public Employee(int no, string name, string role)
        {
            this.No = no;
            this.Name = name;
            this.Role = role;            
        }
        [XmlAttribute(AttributeName="no")]
        public int No { get; set; }
        [XmlElement(ElementName="name")]
        public string Name { get; set; }
        [XmlElement(ElementName="role")]
        public string Role { get; set; }
        public override string ToString()
        {
            return string.Format("[{0},{1},{2}]", No, Name, Role);
        }

    }
    [XmlRoot(ElementName="employees")]
    public class Employees
    {
        [XmlElement(ElementName="employee")]
        public List<Employee> EmployeeList { get; set; }
        public Employees()
        {
            this.EmployeeList = new List<Employee>();
        }
        public override string ToString()
        {
            return "{" + string.Join(",", EmployeeList.ConvertAll(e => e.ToString()).ToArray()) + "}";
        }
    }
    public class Program
    {
        private const String XML_FILE = @"C:\work\employees.xml";
        public static void Main(string[] args)
        {
            // setup context
            XmlSerializer ser = new XmlSerializer(typeof(Employees));
            // read from file
            Employees employees = (Employees)ser.Deserialize(new StreamReader(XML_FILE));
            // add employee
            employees.EmployeeList.Add(new Employee(4, "Dave D", "Intern"));
            // write out
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                ser.Serialize(sw, employees);    
            }
            Console.ReadKey();
        }
    }
}

The attributes XmlAttribute and XmlElement simply tell whether data is an attribute or an element. Attribute XmlRoot tell that this is the top class.

If the XML is documented in an XML schema (XSD file), then one does not need to write the data classes manually. Instead they can be generated from the schema.

Command line:

xsd /classes /language:csorvb /namespace:namespaceforgeneratedclasses nameofschemafile.xsd
Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Linq
Imports System.Xml.Serialization

Namespace XmlProc.Binding
    Public Class Employee
        Public Sub New()
            Me.New(0, "", "")
        End Sub
        Public Sub New(no As Integer, name As String, role As String)
            Me.No = no
            Me.Name = name
            Me.Role = role
        End Sub
        <XmlAttribute(AttributeName := "no")> _
        Public Property No() As Integer
        <XmlElement(ElementName := "name")> _
        Public Property Name() As String
        <XmlElement(ElementName := "role")> _
        Public Property Role() As String
        Public Overrides Function ToString() As String
            Return String.Format("[{0},{1},{2}]", No, Name, Role)
        End Function

    End Class
    <XmlRoot(ElementName := "employees")> _
    Public Class Employees
        <XmlElement(ElementName := "employee")> _
        Public Property EmployeeList() As List(Of Employee)
        Public Sub New()
            Me.EmployeeList = New List(Of Employee)()
        End Sub
        Public Overrides Function ToString() As String
            Return "{" & String.Join(",", EmployeeList.ConvertAll(Function(e) e.ToString()).ToArray()) & "}"
        End Function
    End Class
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Public Shared Sub Main(args As String())
            ' setup context
            Dim ser As New XmlSerializer(GetType(Employees))
            ' read from file
            Dim employees As Employees = DirectCast(ser.Deserialize(New StreamReader(XML_FILE)), Employees)
            ' add employee
            employees.EmployeeList.Add(New Employee(4, "Dave D", "Intern"))
            ' write out
            Using sw As New StreamWriter("C:\work\employees2.xml")
                ser.Serialize(sw, employees)
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace

The attributes XmlAttribute and XmlElement simply tell whether data is an attribute or an element. Attribute XmlRoot tell that this is the top class.

If the XML is documented in an XML schema (XSD file), then one does not need to write the data classes manually. Instead they can be generated from the schema.

Command line:

xsd /classes /language:csorvb /namespace:namespaceforgeneratedclasses nameofschemafile.xsd

Streaming write:

XML can obviously be written using standard IO library. Streaming write is a simple wrapper on top of standard IO that makes it sligthly easier to write well formed XML.

It is closely related to streaming pull parser - one is get/read and the other is put/write.

package xmlproc;

public class Employee {
    private int no;
    private String name;
    private String role;
    public Employee() {
        this(0, null, null);
    }
    public Employee(int no, String name, String role) {
        this.no = no;
        this.name = name;
        this.role = role;
    }
    public int getNo() {
        return no;
    }
    public void setNo(int no) {
        this.no = no;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }
    @Override
    public String toString() {
        return String.format("[%d,%s,%s]", no, name, role);
    }
}
package xmlproc;

import java.util.ArrayList;
import java.util.List;

public class Employees {
    private List<Employee> list = new ArrayList<>();
    public List<Employee> getList(){
        return list;
    }
    public void setList(List<Employee> list) {
        this.list = list;
    }
    @Override
    public String toString() {
        return list.toString();
    }
}
package xmlproc;

import java.io.FileOutputStream;
import java.io.OutputStream;

import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamWriter;

public class WriteStAX {
    public static void main(String[] args) throws Exception {
        // create employees
        Employees employees = new Employees();
        employees.getList().add(new Employee(1, "Alan A", "Manager"));
        employees.getList().add(new Employee(2, "Brian B", "Engineer"));
        employees.getList().add(new Employee(3, "Chris C", "Sales rep"));
        employees.getList().add(new Employee(4, "Dave D", "Intern"));
        // write out
        XMLOutputFactory xof = XMLOutputFactory.newInstance();
        OutputStream os = new FileOutputStream("/work/employees2.xml");
        XMLStreamWriter xsw = xof.createXMLStreamWriter(os);
        xsw.writeStartDocument();
        xsw.writeStartElement("employees");
        for(Employee employee : employees.getList()) {
            xsw.writeStartElement("employee");
            xsw.writeAttribute("no", Integer.toString(employee.getNo()));
            xsw.writeStartElement("name");
            xsw.writeCharacters(employee.getName());
            xsw.writeEndElement();
            xsw.writeStartElement("role");
            xsw.writeCharacters(employee.getRole());
            xsw.writeEndElement();
            xsw.writeEndElement();
        }
        xsw.writeEndElement();
        xsw.writeEndDocument();
        xsw.close();
        os.close();
    }
}

Note that it can not output nicely formatted XML.

This is a major flaw in my opinion.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Xml;

namespace XmlProc.Write
{
    public class Employee
    {
        public Employee() : this(0, "", "")
        {
        }
        public Employee(int no, string name, string role)
        {
            this.No = no;
            this.Name = name;
            this.Role = role;            
        }
        public int No { get; set; }
        public string Name { get; set; }
        public string Role { get; set; }
        public override string ToString()
        {
            return string.Format("[{0},{1},{2}]", No, Name, Role);
        }

    }
    public class Employees
    {
        public List<Employee> EmployeeList { get; set; }
        public Employees()
        {
            this.EmployeeList = new List<Employee>();
        }
        public override string ToString()
        {
            return "{" + string.Join(",", EmployeeList.ConvertAll(e => e.ToString()).ToArray()) + "}";
        }
    }
    public class Program
    {
        public static void Main(string[] args)
        {
            // create employees
            Employees employees = new Employees();
            employees.EmployeeList.Add(new Employee(1, "Alan A", "Manager"));
            employees.EmployeeList.Add(new Employee(2, "Brian B", "Engineer"));
            employees.EmployeeList.Add(new Employee(3, "Chris C", "Sales rep"));
            employees.EmployeeList.Add(new Employee(4, "Dave D", "Intern"));
            // write out
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                XmlWriterSettings xws = new XmlWriterSettings();
                xws.Indent = true;
                XmlWriter xw = XmlWriter.Create(sw, xws);
                xw.WriteStartDocument();
                xw.WriteStartElement("employees");
                foreach(Employee employee in employees.EmployeeList)
                {
                    xw.WriteStartElement("employee"); 
                    xw.WriteAttributeString("no", employee.No.ToString());
                    xw.WriteStartElement("name");
                    xw.WriteString(employee.Name);
                    xw.WriteEndElement();                    
                    xw.WriteStartElement("role"); 
                    xw.WriteString(employee.Role);
                    xw.WriteEndElement();                    
                    xw.WriteEndElement();                    
                }
                xw.WriteEndElement();
                xw.WriteEndDocument();
                xw.Close();
            }
            Console.ReadKey();
        }
    }
}
Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Linq
Imports System.Xml

Namespace XmlProc.Write
    Public Class Employee
        Public Sub New()
            Me.New(0, "", "")
        End Sub
        Public Sub New(no As Integer, name As String, role As String)
            Me.No = no
            Me.Name = name
            Me.Role = role
        End Sub
        Public Property No() As Integer
        Public Property Name() As String
        Public Property Role() As String
        Public Overrides Function ToString() As String
            Return String.Format("[{0},{1},{2}]", No, Name, Role)
        End Function

    End Class
    Public Class Employees
        Public Property EmployeeList() As List(Of Employee)
        Public Sub New()
            Me.EmployeeList = New List(Of Employee)()
        End Sub
        Public Overrides Function ToString() As String
            Return "{" & String.Join(",", EmployeeList.ConvertAll(Function(e) e.ToString()).ToArray()) & "}"
        End Function
    End Class
    Public Class Program
        Public Shared Sub Main(args As String())
            ' create employees
            Dim employees As New Employees()
            employees.EmployeeList.Add(New Employee(1, "Alan A", "Manager"))
            employees.EmployeeList.Add(New Employee(2, "Brian B", "Engineer"))
            employees.EmployeeList.Add(New Employee(3, "Chris C", "Sales rep"))
            employees.EmployeeList.Add(New Employee(4, "Dave D", "Intern"))
            ' write out
            Using sw As New StreamWriter("C:\work\employees2.xml")
                Dim xws As New XmlWriterSettings()
                xws.Indent = True
                Dim xw As XmlWriter = XmlWriter.Create(sw, xws)
                xw.WriteStartDocument()
                xw.WriteStartElement("employees")
                For Each employee As Employee In employees.EmployeeList
                    xw.WriteStartElement("employee")
                    xw.WriteAttributeString("no", employee.No.ToString())
                    xw.WriteStartElement("name")
                    xw.WriteString(employee.Name)
                    xw.WriteEndElement()
                    xw.WriteStartElement("role")
                    xw.WriteString(employee.Role)
                    xw.WriteEndElement()
                    xw.WriteEndElement()
                Next
                xw.WriteEndElement()
                xw.WriteEndDocument()
                xw.Close()
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace
<?php
class Employee {
    public $no;
    public $name;
    public $role;
    public function __construct($no = 0, $name = '', $role = '') {
        $this->no = $no;
        $this->name = $name;
        $this->role = $role;
    }
    function __toString() {
        return sprintf('[%d,%s,%s]', $this->no, $this->name, $this->role);
    }
}

class Employees {
    public $list;
    public function __construct() {
        $this->list = array();
    }
    function __toString() {
        return '{' . implode(',', $this->list) . '}';
    }
}

// create employees
$employees = new Employees();
$employees->list[] = new Employee(1, 'Alan A', 'Manager');
$employees->list[] = new Employee(2, 'Brian B', 'Engineer');
$employees->list[] = new Employee(3, 'Chris C', 'Sales rep');
$employees->list[] = new Employee(4, 'Dave D', 'Intern');

// write out
$wrt = new XMLWriter();
$wrt->openURI('php://output');
$wrt->setIndent(true);
$wrt->startDocument();
$wrt->startElement('employees');
foreach($employees->list as $employee) {
    $wrt->startElement('employee');
    $wrt->startAttribute('no');
    $wrt->text($employee->no);
    $wrt->endAttribute();
    $wrt->startElement('name');
    $wrt->text($employee->name);
    $wrt->endElement();
    $wrt->startElement('role');
    $wrt->text($employee->role);
    $wrt->endElement();
    $wrt->endElement();
    
}
$wrt->endElement();
$wrt->endDocument();
?>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/xmlwriter.h>

struct employee
{
    int no;
    char *name;
    char *role;
};

int main()
{
    struct employee employees[] = { { 1, "Alan A", "Manager" },
                                    { 2, "Brian B", "Engineer" },
                                    { 3, "Chris C", "Sales rep"},
                                    { 4, "Dave D", "Intern"} };
    xmlTextWriter *xw;
    char temp[20];
    int i;
    xw = xmlNewTextWriterFilename("employees2.xml", 0);
    if(xw != NULL)
    {
        xmlTextWriterSetIndent(xw, 1);
        xmlTextWriterStartDocument(xw, "1.0", "UTF-8", "Yes");
        xmlTextWriterStartElement(xw, "employees");
        for(i = 0; i < 4; i++)
        {
            xmlTextWriterStartElement(xw, "employee");
            xmlTextWriterWriteAttribute(xw, "no", itoa(employees[i].no, temp, 10));
            xmlTextWriterStartElement(xw, "name");
            xmlTextWriterWriteString(xw, employees[i].name);
            xmlTextWriterEndElement(xw);
            xmlTextWriterStartElement(xw, "role");
            xmlTextWriterWriteString(xw, employees[i].role);
            xmlTextWriterEndElement(xw);
            xmlTextWriterEndElement(xw);
        }
        xmlTextWriterEndElement(xw);
        xmlTextWriterEndDocument(xw);
        xmlFreeTextWriter(xw);
    }
    else
    {
        fprintf(stderr, "Unable to create XML file\n");
    }
    return EXIT_SUCCESS;
}

Serialization:

XML serialization is the text equivalent of binary serialization. Objects can be serialized to XML and that XML can be deserialized to objects again.

Pro's:

Con's:

package xmlproc;

public class Employee {
    private int no;
    private String name;
    private String role;
    public Employee() {
        this(0, null, null);
    }
    public Employee(int no, String name, String role) {
        this.no = no;
        this.name = name;
        this.role = role;
    }
    public int getNo() {
        return no;
    }
    public void setNo(int no) {
        this.no = no;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }
    @Override
    public String toString() {
        return String.format("[%d,%s,%s]", no, name, role);
    }
}
package xmlproc;

import java.util.ArrayList;
import java.util.List;

public class Employees {
    private List<Employee> list = new ArrayList<>();
    public List<Employee> getList(){
        return list;
    }
    public void setList(List<Employee> list) {
        this.list = list;
    }
    @Override
    public String toString() {
        return list.toString();
    }
}
package xmlproc;

import java.beans.XMLDecoder;
import java.beans.XMLEncoder;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class JavaBeansSer {
    public static void main(String[] args) throws Exception {
        // create employees
        Employees employees = new Employees();
        employees.getList().add(new Employee(1, "Alan A", "Manager"));
        employees.getList().add(new Employee(2, "Brian B", "Engineer"));
        employees.getList().add(new Employee(3, "Chris C", "Sales rep"));
        employees.getList().add(new Employee(4, "Dave D", "Intern"));
        // write out
        OutputStream os = new FileOutputStream("/work/employees2.xml");
        XMLEncoder enc = new XMLEncoder(os);
        enc.writeObject(employees);
        enc.close();
        // read in
        InputStream is = new FileInputStream("/work/employees2.xml");
        XMLDecoder dec = new XMLDecoder(is);
        Employees copy = (Employees)dec.readObject();
        dec.close();
        System.out.println(copy);
    }
}

Generated XML looks like:

<?xml version="1.0" encoding="UTF-8"?>
<java version="1.8.0_91" class="java.beans.XMLDecoder">
 <object class="xmlproc.Employees" id="Employees0">
  <void property="list">
   <void method="add">
    <object class="xmlproc.Employee">
     <void property="name">
      <string>Alan A</string>
     </void>
     <void property="no">
      <int>1</int>
     </void>
     <void property="role">
      <string>Manager</string>
     </void>
    </object>
   </void>
   <void method="add">
    <object class="xmlproc.Employee">
     <void property="name">
      <string>Brian B</string>
     </void>
     <void property="no">
      <int>2</int>
     </void>
     <void property="role">
      <string>Engineer</string>
     </void>
    </object>
   </void>
   <void method="add">
    <object class="xmlproc.Employee">
     <void property="name">
      <string>Chris C</string>
     </void>
     <void property="no">
      <int>3</int>
     </void>
     <void property="role">
      <string>Sales rep</string>
     </void>
    </object>
   </void>
   <void method="add">
    <object class="xmlproc.Employee">
     <void property="name">
      <string>Dave D</string>
     </void>
     <void property="no">
      <int>4</int>
     </void>
     <void property="role">
      <string>Intern</string>
     </void>
    </object>
   </void>
  </void>
 </object>
</java>

The format sure makes sense for Java, but not for any other programming language.

package xmlproc;

public class Employee {
    private int no;
    private String name;
    private String role;
    public Employee() {
        this(0, null, null);
    }
    public Employee(int no, String name, String role) {
        this.no = no;
        this.name = name;
        this.role = role;
    }
    public int getNo() {
        return no;
    }
    public void setNo(int no) {
        this.no = no;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }
    @Override
    public String toString() {
        return String.format("[%d,%s,%s]", no, name, role);
    }
}
package xmlproc;

import java.util.ArrayList;
import java.util.List;

public class Employees {
    private List<Employee> list = new ArrayList<>();
    public List<Employee> getList(){
        return list;
    }
    public void setList(List<Employee> list) {
        this.list = list;
    }
    @Override
    public String toString() {
        return list.toString();
    }
}
package xmlproc;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

public class XStreamSer {
    public static void main(String[] args) throws Exception {
        // create employees
        Employees employees = new Employees();
        employees.getList().add(new Employee(1, "Alan A", "Manager"));
        employees.getList().add(new Employee(2, "Brian B", "Engineer"));
        employees.getList().add(new Employee(3, "Chris C", "Sales rep"));
        employees.getList().add(new Employee(4, "Dave D", "Intern"));
        // setup XStream
        XStream xs = new XStream(new DomDriver());
        xs.alias("employees", Employees.class);
        xs.alias("employee", Employee.class);
        // write out
        OutputStream os = new FileOutputStream("/work/employees2.xml");
        xs.toXML(employees, os);
        os.close();
        // read in
        InputStream is = new FileInputStream("/work/employees2.xml");
        Employees copy = (Employees)xs.fromXML(is);
        is.close();
        System.out.println(copy);
    }
}

Generated XML looks like:

<employees>
  <list>
    <employee>
      <no>1</no>
      <name>Alan A</name>
      <role>Manager</role>
    </employee>
    <employee>
      <no>2</no>
      <name>Brian B</name>
      <role>Engineer</role>
    </employee>
    <employee>
      <no>3</no>
      <name>Chris C</name>
      <role>Sales rep</role>
    </employee>
    <employee>
      <no>4</no>
      <name>Dave D</name>
      <role>Intern</role>
    </employee>
  </list>
</employees>

Which is actually a pretty nice format that could make sense in other programming languages as well.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Xml.Serialization;

namespace XmlProc.Serialize
{
    public class Employee
    {
        public Employee() : this(0, "", "")
        {
        }
        public Employee(int no, string name, string role)
        {
            this.No = no;
            this.Name = name;
            this.Role = role;            
        }
        public int No { get; set; }
        public string Name { get; set; }
        public string Role { get; set; }
        public override string ToString()
        {
            return string.Format("[{0},{1},{2}]", No, Name, Role);
        }

    }
    public class Employees
    {
        public List<Employee> EmployeeList { get; set; }
        public Employees()
        {
            this.EmployeeList = new List<Employee>();
        }
        public override string ToString()
        {
            return "{" + string.Join(",", EmployeeList.ConvertAll(e => e.ToString()).ToArray()) + "}";
        }
    }
    public class Program
    {
        public static void Main(string[] args)
        {
            // create employees
            Employees employees = new Employees();
            employees.EmployeeList.Add(new Employee(1, "Alan A", "Manager"));
            employees.EmployeeList.Add(new Employee(2, "Brian B", "Engineer"));
            employees.EmployeeList.Add(new Employee(3, "Chris C", "Sales rep"));
            employees.EmployeeList.Add(new Employee(4, "Dave D", "Intern"));
            // setup context
            XmlSerializer ser = new XmlSerializer(typeof(Employees));
            // write out
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                ser.Serialize(sw, employees);    
            }
            // read in
            Employees copy;
            using(StreamReader sr = new StreamReader(@"C:\work\employees2.xml"))
            {
                copy = (Employees)ser.Deserialize(sr);
            }
            Console.WriteLine(copy);
            Console.ReadKey();
        }
    }
}

Generated XML looks like:

<?xml version="1.0" encoding="utf-8"?>
<Employees xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <EmployeeList>
    <Employee>
      <No>1</No>
      <Name>Alan A</Name>
      <Role>Manager</Role>
    </Employee>
    <Employee>
      <No>2</No>
      <Name>Brian B</Name>
      <Role>Engineer</Role>
    </Employee>
    <Employee>
      <No>3</No>
      <Name>Chris C</Name>
      <Role>Sales rep</Role>
    </Employee>
    <Employee>
      <No>4</No>
      <Name>Dave D</Name>
      <Role>Intern</Role>
    </Employee>
  </EmployeeList>
</Employees>

Which is actually a pretty nice format that could make sense in other programming languages as well.

Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.Linq
Imports System.Xml.Serialization

Namespace XmlProc.Serialize
    Public Class Employee
        Public Sub New()
            Me.New(0, "", "")
        End Sub
        Public Sub New(no As Integer, name As String, role As String)
            Me.No = no
            Me.Name = name
            Me.Role = role
        End Sub
        Public Property No() As Integer
        Public Property Name() As String
        Public Property Role() As String
        Public Overrides Function ToString() As String
            Return String.Format("[{0},{1},{2}]", No, Name, Role)
        End Function

    End Class
    Public Class Employees
        Public Property EmployeeList() As List(Of Employee)
        Public Sub New()
            Me.EmployeeList = New List(Of Employee)()
        End Sub
        Public Overrides Function ToString() As String
            Return "{" & String.Join(",", EmployeeList.ConvertAll(Function(e) e.ToString()).ToArray()) & "}"
        End Function
    End Class
    Public Class Program
        Public Shared Sub Main(args As String())
            ' create employees
            Dim employees As New Employees()
            employees.EmployeeList.Add(New Employee(1, "Alan A", "Manager"))
            employees.EmployeeList.Add(New Employee(2, "Brian B", "Engineer"))
            employees.EmployeeList.Add(New Employee(3, "Chris C", "Sales rep"))
            employees.EmployeeList.Add(New Employee(4, "Dave D", "Intern"))
            ' setup context
            Dim ser As New XmlSerializer(GetType(Employees))
            ' write out
            Using sw As New StreamWriter("C:\work\employees2.xml")
                ser.Serialize(sw, employees)
            End Using
            ' read in
            Dim copy As Employees
            Using sr As New StreamReader("C:\work\employees2.xml")
                copy = DirectCast(ser.Deserialize(sr), Employees)
            End Using
            Console.WriteLine(copy)
            Console.ReadKey()
        End Sub
    End Class
End Namespace

Generated XML looks like:

<?xml version="1.0" encoding="utf-8"?>
<Employees xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <EmployeeList>
    <Employee>
      <No>1</No>
      <Name>Alan A</Name>
      <Role>Manager</Role>
    </Employee>
    <Employee>
      <No>2</No>
      <Name>Brian B</Name>
      <Role>Engineer</Role>
    </Employee>
    <Employee>
      <No>3</No>
      <Name>Chris C</Name>
      <Role>Sales rep</Role>
    </Employee>
    <Employee>
      <No>4</No>
      <Name>Dave D</Name>
      <Role>Intern</Role>
    </Employee>
  </EmployeeList>
</Employees>

Which is actually a pretty nice format that could make sense in other programming languages as well.

<?php
require_once 'XML/Serializer.php';
require_once 'XML/Unserializer.php';

class Employee {
    public $no;
    public $name;
    public $role;
    public function __construct($no = 0, $name = '', $role = '') {
        $this->no = $no;
        $this->name = $name;
        $this->role = $role;
    }
    function __toString() {
        return sprintf('[%d,%s,%s]', $this->no, $this->name, $this->role);
    }
}

class Employees {
    public $list;
    public function __construct() {
        $this->list = array();
    }
    function __toString() {
        return '{' . implode(',', $this->list) . '}';
    }
}

// create employees
$employees = new Employees();
$employees->list[] = new Employee(1, 'Alan A', 'Manager');
$employees->list[] = new Employee(2, 'Brian B', 'Engineer');
$employees->list[] = new Employee(3, 'Chris C', 'Sales rep');
$employees->list[] = new Employee(4, 'Dave D', 'Intern');

// write out
$serializer = new XML_Serializer(array('indent' => '    ', 'typeHints' => true));
$serializer->serialize($employees);
$xml = $serializer->getSerializedData();
echo $xml;

// read in
$unserializer = new XML_Unserializer(array());
$unserializer->unserialize($xml);
$o = $unserializer->getUnserializedData();
echo $o;
?>

Generated XML looks like:

<Employees _class="Employees" _type="object">
    <list _type="array">
        <XML_Serializer_Tag _class="Employee" _originalKey="0" _type="object">
            <no _type="integer">1</no>
            <name _type="string">Alan A</name>
            <role _type="string">Manager</role>
        </XML_Serializer_Tag>
        <XML_Serializer_Tag _class="Employee" _originalKey="1" _type="object">
            <no _type="integer">2</no>
            <name _type="string">Brian B</name>
            <role _type="string">Engineer</role>
        </XML_Serializer_Tag>
        <XML_Serializer_Tag _class="Employee" _originalKey="2" _type="object">
            <no _type="integer">3</no>
            <name _type="string">Chris C</name>
            <role _type="string">Sales rep</role>
        </XML_Serializer_Tag>
        <XML_Serializer_Tag _class="Employee" _originalKey="3" _type="object">
            <no _type="integer">4</no>
            <name _type="string">Dave D</name>
            <role _type="string">Intern</role>
        </XML_Serializer_Tag>
    </list>
</Employees>

The format sure makes sense for PHP, but not for any other programming language.

XPath:

XPath is an expression language for selcting from XML. Or to put it in another way: XPath is to XML what SQL is to relational databases.

Any serious developer should know XPath.

XPath syntax:

/elm1/elm2/elm3
elm3 elements under an elm2 element under an elm1 element
//elm
elm elements anywhere
@a
attribute a under current node
elm/text()
element elm under current node text value
/elm[@a=123]
elm elements where attribute a is '123'
package xmlproc;

import java.io.File;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class W3CDOM_XPath {
    private final static String XML_FILE = "/work/employees.xml";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document doc = db.parse(new File(XML_FILE));
        // setup XPath
        XPath xpath = XPathFactory.newInstance().newXPath();
        // iterate over all employee elements
        NodeList employees = (NodeList)xpath.evaluate("//employee[@no>1 and role!='Intern']", doc.getDocumentElement(), XPathConstants.NODESET);
        for (int i = 0; i < employees.getLength(); i++) {
            Element employee = (Element)employees.item(i);
            // find attribute no
            String no = (String)xpath.evaluate("@no", employee, XPathConstants.STRING);
            // find sub elements name and role 
            String name = (String)xpath.evaluate("name/text()", employee, XPathConstants.STRING);
            String role = (String)xpath.evaluate("role/text()", employee, XPathConstants.STRING);
            // print
            System.out.println("no=" + no);
            System.out.println("name=" + name);
            System.out.println("role=" + role);
        }
    }
}

XPath API in JDOM is not very well implemented, and I don't think anyone will want to use that, so I will not show that.

package xmlproc;

import java.util.List;

import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

public class DOM4J_XPath {
    private final static String XML_FILE = "/work/employees.xml";
    @SuppressWarnings("unchecked")
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        SAXReader xmlReader = new SAXReader();
        Document doc = xmlReader.read(XML_FILE);
        // iterate over all employee elements
        for(Element employee : (List<Element>)doc.getRootElement().selectNodes("//employee[@no>1 and role!='Intern']")) {
            // find attribute no
            String no = employee.selectSingleNode("@no").getText();
            // find sub elements name and role
            String name = employee.selectSingleNode("name/text()").getText();
            String role = employee.selectSingleNode("role/text()").getText();
            // print
            System.out.println("no=" + no);
            System.out.println("name=" + name);
            System.out.println("role=" + role);
        }
    }
}
using System;
using System.IO;
using System.Xml;

namespace XmlProc.XPath
{
    public class Program
    {
        private const String XML_FILE = @"C:\work\employees.xml";
        public static void Main(string[] args)
        {
            // read from file to DOM tree
            XmlDocument doc = new XmlDocument();
            doc.Load(XML_FILE);
            // iterate over all employee elements
            foreach(XmlElement employee in doc.SelectNodes("//employee[@no>1 and role!='Intern']"))
            {
                // find attribute no
                string no = employee.SelectSingleNode("@no").Value;
                // find sub elements name and role
                string name = employee.SelectSingleNode("name/text()").Value;
                string role = employee.SelectSingleNode("role/text()").Value;
                // print
                Console.WriteLine("no = " + no);
                Console.WriteLine("name = " + name);
                Console.WriteLine("role = " + role);
            }
            Console.ReadKey();
        }
    }
}
Imports System
Imports System.IO
Imports System.Xml

Namespace XmlProc.XPath
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Public Shared Sub Main(args As String())
            ' read from file to DOM tree
            Dim doc As New XmlDocument()
            doc.Load(XML_FILE)
            ' iterate over all employee elements
            For Each employee As XmlElement In doc.SelectNodes("//employee[@no>1 and role!='Intern']")
                ' find attribute no
                Dim no As String = employee.SelectSingleNode("@no").Value
                ' find sub elements name and role
                Dim name As String = employee.SelectSingleNode("name/text()").Value
                Dim role As String = employee.SelectSingleNode("role/text()").Value
                ' print
                Console.WriteLine("no = " & no)
                Console.WriteLine("name = " & name)
                Console.WriteLine("role = " & role)
            Next
            Console.ReadKey()
        End Sub
    End Class
End Namespace
<html>
<head>
<title>W3C DOM XPath</title>
</head>
<body>
<h1>W3C DOM XPath</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// read from file to DOM tree
$doc = new DOMDocument();
$doc->load(XML_FILE);
// setup XPath
$xpath = new DOMXPath($doc);
// iterate over all employee elements
$employees = $xpath->query("//employee[@no>1 and role!='Intern']", $doc);
foreach($employees as $employee) {
    // find attribute no
    $no = $xpath->query("@no", $employee)->item(0)->nodeValue;
    // find sub elements name and role
    $name = $xpath->query("name/text()", $employee)->item(0)->nodeValue;
    $role = $xpath->query("role/text()", $employee)->item(0)->nodeValue;
    // print
    echo "<tr>\r\n";
    echo "<td>$no</td>\r\n";
    echo "<td>$name</td>\r\n";
    echo "<td>$role</td>\r\n";
    echo "</tr>\r\n";
}
?>
</table>
</body>
</html>
<html>
<head>
<title>SimpleXML XPath</title>
</head>
<body>
<h1>SimpleXML XPath</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<?php
define('XML_FILE','/work/employees.xml');
// read from file to pseudo DOM tree
$xml = new SimpleXMLElement(file_get_contents(XML_FILE));
// iterate over all employee elements
foreach($xml->xpath("//employee[@no>1 and role!='Intern']") as $employee) {
    // find attribute no
    $no = $employee->xpath("@no")[0];
    // find sub elements name and role
    $name = $employee->xpath("name/text()")[0];
    $role = $employee->xpath("role/text()")[0];
    // print
    echo "<tr>\r\n";
    echo "<td>$no</td>\r\n";
    echo "<td>$name</td>\r\n";
    echo "<td>$role</td>\r\n";
    echo "</tr>\r\n";
}
?>
</table>
</body>
</html>
<html>
<head>
<title>W3C DOM XPath</title>
</head>
<body>
<h1>W3C DOM XPath</h1>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<%
' read from file to DOM tree
Set doc = CreateObject("MSXML.DOMDocument")
doc.Async = False
doc.Load("C:\work\employees.xml")
' iterate over all employee elements
Set employees = doc.SelectNodes("//employee[@no>1 and role!='Intern']")
For Each employee in employees
    ' find attribute no
    no = employee.SelectSingleNode("@no").NodeValue
    ' find sub elements name and role
    name = employee.SelectSingleNode("name/text()").NodeValue
    role = employee.SelectSingleNode("role/text()").NodeValue
    ' print
    Response.Write "<tr>" & vbCrLf
    Response.Write "<td>" & no & "</td>" & vbCrLf
    Response.Write "<td>" & name & "</td>" & vbCrLf
    Response.Write "<td>" & role & "</td>" & vbCrLf
    Response.Write "</tr>" & vbCrLf
Next
Response.Write  "</table>" & vbCrLf
' cleanup
Set employees = Nothing
Set doc = Nothing
%>
</body>
</html>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/parser.h>
#include <libxml/tree.h>
#include <libxml/xpath.h>

#define XML_FILE "employees.xml"

int main()
{
    xmlDoc *doc;
    xmlXPathContext *ctx;
    xmlXPathObject *res;
    xmlXPathObject *res2;
    xmlNodeSet *employees;
    xmlNode *employee;
    xmlChar *no;
    xmlChar *name;
    xmlChar *role;
    int i;
    /* read from file to DOM tree */
    doc = xmlReadFile(XML_FILE, NULL, 0);
    if (doc == NULL)
    {
        fprintf(stderr, "Failed to parse %s\n", XML_FILE);
        return EXIT_FAILURE;
    }
    /* setup XPath */
    ctx = xmlXPathNewContext(doc);
    /* iterate over all employee elements */
    res = xmlXPathEval("//employee[@no>1 and role!='Intern']", ctx);
    employees = res->nodesetval;
    if(!xmlXPathNodeSetIsEmpty(employees))
    {
        for(i = 0; i < xmlXPathNodeSetGetLength(employees); i++)
        {
            employee = xmlXPathNodeSetItem(employees, i);
            // find attribute no
            res2 = xmlXPathNodeEval(employee, "@no", ctx);
            no = xmlXPathCastNodeSetToString(res2->nodesetval);
            // find sub elements name and role 
            res2 = xmlXPathNodeEval(employee, "name/text()", ctx);
            name = xmlXPathCastNodeSetToString(res2->nodesetval);
            res2 = xmlXPathNodeEval(employee, "role/text()", ctx);
            role = xmlXPathCastNodeSetToString(res2->nodesetval);
            /* print */
            printf("no=%s\n", no);
            printf("name=%s\n", name);
            printf("role=%s\n", role);
       }
    }
    /* clean up */
    xmlXPathFreeObject(res);
    xmlXPathFreeContext(ctx);
    xmlFreeDoc(doc);
    xmlCleanupParser();
    /* */
    return EXIT_SUCCESS;
}

Note that xmlXPathNodeEval requires a relative new version of LIBXML2.

program XPathEx;

uses
   Classes, DOM, XMLRead, XMLWrite, XPath;

const
  XML_FILE = 'employees.xml';

var
   doc : TXMLDocument;
   employees : TNodeSet;
   employee : TDOMNode;
   no, name, role : WideString;
   i : integer;

begin
  (* read from file to DOM tree *)
  ReadXMLfile(doc, XML_FILE);
  (* iterate over all employee elements *)
  employees := EvaluateXPathExpression('//employee[@no>1 and role!="Intern"]', doc.DocumentElement).AsNodeSet;
  for i := 0 to employees.Count - 1 do begin
    employee := TDOMNode(employees.Items[i]);
    (* find attribute no *)
    no := employee.Attributes.GetNamedItem('no').NodeValue;
    (* find sub elements name and role  *)
    name := EvaluateXPathExpression('name/text()', employee).AsText;
    role := EvaluateXPathExpression('role/text()', employee).AsText;
    (* print *)
    writeln('no=', no);
    writeln('name=', name);
    writeln('role=', role);
  end;
  (* *)
  doc.Free;
end.

XSLT transformation:

XSL is a transformation language for XML (and is an XML format itself). XSLT is transformation of XML using XSL.

XSL can be a little tricky to learn for developers as it is a declarative language and not a sequential language.

XSL is a big topic so I will not describe it in detail just provide a small example.

employees.xsl:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
<xsl:template match='/'>
<allemployees>
<xsl:for-each select='//employee'>
  <oneemployee>
    <no><xsl:value-of select='@no'/></no>
    <name><xsl:value-of select='name'/></name>
    <job><xsl:value-of select='role'/></job>
  </oneemployee>
</xsl:for-each>
</allemployees>
</xsl:template>
</xsl:stylesheet>

It does a simple transformation from XML to XML:

Note that XSL uses XPath!

employeeshtml.xsl:

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
<xsl:output method='html'/>
<xsl:template match='/'>
<html>
<head>
<title>XSLT demo</title>
</head>
<body>
<h2>XSLT demo</h2>
<table>
<tr>
<th>No</th>
<th>Name</th>
<th>Role</th>
</tr>
<xsl:for-each select='//employee'>
  <tr>
    <td><xsl:value-of select='@no'/></td>
    <td><xsl:value-of select='name'/></td>
    <td><xsl:value-of select='role'/></td>
  </tr>
</xsl:for-each>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

It does a simple transformation from XML to HTML (formats result as a HTML table).

package xmlproc;

import java.io.File;

import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class XSLT {
    private final static String XML_FILE = "/work/employees.xml";
    private final static String XSL_FILE = "/work/employees.xsl";
    public static void main(String[] args) throws Exception {
        // transform from one file to another file
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer(new StreamSource(new File(XSL_FILE)));
        t.setOutputProperty(OutputKeys.INDENT, "yes");
        t.transform(new StreamSource(new File(XML_FILE)), new StreamResult(new File("/work/employees2.xml")));
    }
}
package xmlproc;

import java.io.File;
import java.io.FileWriter;
import java.io.Writer;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.bootstrap.DOMImplementationRegistry;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSSerializer;

public class W3CDOM_XSLT {
    private final static String XML_FILE = "/work/employees.xml";
    private final static String XSL_FILE = "/work/employees.xsl";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document doc = db.parse(new File(XML_FILE));
        // transform from one dom to another dom
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer(new StreamSource(new File(XSL_FILE)));
        Document doc2 = db.newDocument();
        t.transform(new DOMSource(doc), new DOMResult(doc2));
        // write out
        DOMImplementation impl = DOMImplementationRegistry.newInstance().getDOMImplementation("XML 3.0");
        DOMImplementationLS feature = (DOMImplementationLS)impl.getFeature("LS","3.0");
        LSSerializer ser = feature.createLSSerializer();
        ser.getDomConfig().setParameter("format-pretty-print", true);
        LSOutput output = feature.createLSOutput();
        Writer w = new FileWriter("/work/employees2.xml");
        output.setCharacterStream(w);
        ser.write(doc2, output);
        w.close();
    }
}
package xmlproc;

import java.io.FileWriter;
import java.io.Writer;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;

import org.jdom2.transform.JDOMResult;
import org.jdom2.transform.JDOMSource;
import org.jdom2.Document;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

public class JDOM2_XSLT {
    private final static String XML_FILE = "/work/employees.xml";
    private final static String XSL_FILE = "/work/employees.xsl";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        SAXBuilder b = new SAXBuilder();
        Document doc = b.build(XML_FILE);
        // transform from one dom to another dom
        Document xsl = b.build(XSL_FILE);
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer(new JDOMSource(xsl));
        JDOMResult res = new JDOMResult();
        t.transform(new JDOMSource(doc), res);
        Document doc2 = res.getDocument();
        // write out
        XMLOutputter fmt = new XMLOutputter(Format.getPrettyFormat());
        Writer w = new FileWriter("/work/employees2.xml");
        w.write(fmt.outputString(doc2));
        w.close();
    }
}
package xmlproc;

import java.io.File;
import java.io.FileOutputStream;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamSource;

import org.dom4j.Document;
import org.dom4j.io.DocumentResult;
import org.dom4j.io.DocumentSource;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

public class DOM4J_XSLT {
    private final static String XML_FILE = "/work/employees.xml";
    private final static String XSL_FILE = "/work/employees.xsl";
    public static void main(String[] args) throws Exception {
        // read from file to DOM tree
        SAXReader xmlReader = new SAXReader();
        Document doc = xmlReader.read(XML_FILE);
        // transform from one dom to another dom
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer(new StreamSource(new File(XSL_FILE)));
        DocumentResult res = new DocumentResult();
        t.transform(new DocumentSource(doc), res);
        Document doc2 = res.getDocument();
        // write out
        OutputFormat of = OutputFormat.createPrettyPrint();
        FileOutputStream fos = new FileOutputStream("/work/employees2.xml");
        XMLWriter xw = new XMLWriter(fos, of);
        xw.write(doc2);
        xw.close();
        fos.close();
    }
}
using System;
using System.IO;
using System.Xml;
using System.Xml.Xsl;

namespace XmlProc.XSLT
{
    public class Program
    {
        private const string XML_FILE = @"C:\work\employees.xml";
        private const string XSL_FILE = @"C:\work\employees.xsl";
        public static void Main(string[] args)
        {
            // transform from one file to another file
            XslCompiledTransform xslt = new XslCompiledTransform();
            xslt.Load(XSL_FILE);
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                XmlWriterSettings xws = new XmlWriterSettings();
                xws.Indent = true;
                XmlWriter xw = XmlWriter.Create(sw, xws);
                xslt.Transform(XML_FILE, xw);
            }
            Console.ReadKey();
        }
    }
}
using System;
using System.IO;
using System.Xml;
using System.Xml.Xsl;

namespace XmlProc.XSLT
{
    public class Program
    {
        private const string XML_FILE = @"C:\work\employees.xml";
        private const string XSL_FILE = @"C:\work\employees.xsl";
        public static void Main(string[] args)
        {
            // read from file to DOM tree
            XmlDocument doc = new XmlDocument();
            doc.Load(XML_FILE);
            // transform from DOM to another file
            XslCompiledTransform xslt = new XslCompiledTransform();
            xslt.Load(XSL_FILE);
            using(StreamWriter sw = new StreamWriter(@"C:\work\employees2.xml"))
            {
                XmlWriterSettings xws = new XmlWriterSettings();
                xws.Indent = true;
                XmlWriter xw = XmlWriter.Create(sw, xws);
                xslt.Transform(doc, xw);
            }
            Console.ReadKey();
        }
    }
}
Imports System
Imports System.IO
Imports System.Xml
Imports System.Xml.Xsl

Namespace XmlProc.XSLT
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Private Const XSL_FILE As String = "C:\work\employees.xsl"
        Public Shared Sub Main(args As String())
            ' transform from one file to another file
            Dim xslt As New XslCompiledTransform()
            xslt.Load(XSL_FILE)
            Using sw As New StreamWriter("C:\work\employees2.xml")
                Dim xws As New XmlWriterSettings()
                xws.Indent = True
                Dim xw As XmlWriter = XmlWriter.Create(sw, xws)
                xslt.Transform(XML_FILE, xw)
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace
Imports System
Imports System.IO
Imports System.Xml
Imports System.Xml.Xsl

Namespace XmlProc.XSLT
    Public Class Program
        Private Const XML_FILE As String = "C:\work\employees.xml"
        Private Const XSL_FILE As String = "C:\work\employees.xsl"
        Public Shared Sub Main(args As String())
            ' read from file to DOM tree
            Dim doc As New XmlDocument()
            doc.Load(XML_FILE)
            ' transform from DOM to another file
            Dim xslt As New XslCompiledTransform()
            xslt.Load(XSL_FILE)
            Using sw As New StreamWriter("C:\work\employees2.xml")
                Dim xws As New XmlWriterSettings()
                xws.Indent = True
                Dim xw As XmlWriter = XmlWriter.Create(sw, xws)
                xslt.Transform(doc, xw)
            End Using
            Console.ReadKey()
        End Sub
    End Class
End Namespace
<?php
define('XML_FILE','/work/employees.xml');
define('XSL_FILE','/work/employeeshtml.xsl');
// read from file to DOM tree
$doc = new DOMDocument();
$doc->load(XML_FILE);
// transform from DOM
$xsl = new DOMDocument();
$xsl->load(XSL_FILE);
$xslt = new XSLTProcessor();
$xslt->importStylesheet($xsl);
echo $xslt->transformToXML($doc);
?>
<?php
define('XML_FILE','/work/employees.xml');
define('XSL_FILE','/work/employeeshtml.xsl');
// read from file to pseudo DOM tree
$xml = new SimpleXMLElement(file_get_contents(XML_FILE));
// transform from SimpleXML
$xsl = new SimpleXMLElement(file_get_contents(XSL_FILE));
$xslt = new XSLTProcessor();
$xslt->importStylesheet($xsl);
echo $xslt->transformToXML($xml);
?>
<%
' read from file to DOM tree
Set doc = CreateObject("MSXML.DOMDocument")
doc.Async = False
doc.Load("C:\work\employees.xml")
' transform from DOM
Set xsl = CreateObject("MSXML.DOMDocument")
xsl.Async = False
xsl.Load("C:\work\employeeshtml.xsl")
Response.Write doc.TransformNode(xsl)
Set doc = Nothing
Set xsl = Nothing
%>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <libxml/parser.h>
#include <libxslt/transform.h>

#define XML_FILE "employees.xml"
#define XSL_FILE "employees.xsl"

int main()
{
    xmlDoc *doc;
    xsltStylesheet *tf;
    xmlDoc *res;
    FILE *fp;
    /* read from file to DOM tree */
    doc = xmlReadFile(XML_FILE, NULL, 0);
    if (doc == NULL)
    {
        fprintf(stderr, "Failed to parse %s\n", XML_FILE);
        return EXIT_FAILURE;
    }
    /* transform from one dom to another dom */
    tf = xsltParseStylesheetFile(XSL_FILE);
    res = xsltApplyStylesheet(tf, doc, NULL);
    /* write out */
    fp = fopen("employees2.xml", "w");
    xmlDocDump(fp, res);
    fclose(fp);
    /* clean up */
    xmlFreeDoc(res);
    xsltFreeStylesheet(tf);
    xmlFreeDoc(doc);
    xmlCleanupParser();
    /* */
    return EXIT_SUCCESS;
}

Article history:

Version Date Description
1.0 September 5th 2016 Initial version based on multiple old articles on Eksperten.dk
1.1 October 7th 2016 Add content overview
1.2 January 14th 2018 Add C examples
1.3 July 29th 2018 Add Delphi/Lazarus examples
1.4 December 26th 2018 Add Python builtin xml examples
1.5 June 1st 2019 Add C++ Xerces examples

Other articles:

See list of all articles here

Comments:

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