Generate XML programatically in Qt

This code snippet shows how to generate XML using QXmlStreamWriter. The QXmlStreamWriter class provides an XML writer with a simple streaming API.

Article Metadata

---

Code Example

Source file: Media:QtGenerateXML.zip

---

Tested with

Devices(s): Nokia 5800 XpressMusic

---

Compatibility

Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition

---

Platform Security

Signing Required: Self-Signed

Capabilities: None

---

Article

Keywords: QXmlStreamWriter

Created: savaj (13 Jun 2009)

Last edited: hamishwillee (11 Oct 2012)

Overview

QXmlStreamWriter is the pendent to QXmlStreamReader for writing XML. Like its related class, it operates on a QIODevice specified with setDevice(). Element tags are opened with writeStartElement() followed by writeAttribute() or writeAttributes(), element content, and then writeEndElement(). A shorter form writeEmptyElement() can be used to write empty elements, followed by writeAttributes().

This snippet can be self-signed.

Headers files

#include <QXmlStreamWriter>
 
class GenerateXML : public QMainWindow
{
    Q_OBJECT
 
public:
	GenerateXML(QWidget *parent = 0);
    ~GenerateXML();
	//call this function to create xml
    void CreateXMLFile();
 
private:
    Ui::GenerateXMLClass ui;
	//variable having data from which we have to generate xml.
	QMap<QString,QString> firstname;
	QMap<QString,QString> surname;
	QMap<QString,QString> phoneNumber;
};

Source

#include "GenerateXML.h"
#include <QMap>
#include <QFile>
#include <QMessageBox>
#include <QXmlStreamWriter>
#include <QMapIterator>
 
// code for constructor
 
GenerateXML::GenerateXML(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);
	setWindowTitle("Generate XML");
 
	/* Assuming user rerived data from which he wants to creare XML.
	* lets we have data of 5 user to create XML.
	*/
	firstname.insertMulti("firstname", "abc");
	firstname.insertMulti("firstname", "ghi");
	firstname.insertMulti("firstname", "mno");
	firstname.insertMulti("firstname", "stu");
	firstname.insertMulti("firstname", "yza");
 
	surname.insertMulti("surname", "def");
	surname.insertMulti("surname", "jkl");
	surname.insertMulti("surname", "pqr");
	surname.insertMulti("surname", "vwx");
	surname.insertMulti("surname", "bcd");
 
	phoneNumber.insertMulti("number", "12345");
	phoneNumber.insertMulti("number", "67890");
	phoneNumber.insertMulti("number", "12356");
	phoneNumber.insertMulti("number", "87654");
	phoneNumber.insertMulti("number", "756776");
 
	/* call method to generate XML */
	CreateXMLFile();
}
 
void GenerateXML::CreateXMLFile()
{
    /* For testing purpose, we generate in C drives,
	QFile file("c://contacts.xml");
 
	/*open a file */
	if (!file.open(QIODevice::WriteOnly))
	{
	/* show wrror message if not able to open file */
	QMessageBox::warning(0, "Read only", "The file is in read only mode");
	}	
	else
	{
		/*if file is successfully opened then create XML*/
		QXmlStreamWriter* xmlWriter = new QXmlStreamWriter();
		/* set device (here file)to streamwriter */
		xmlWriter->setDevice(&file);
		/* Writes a document start with the XML version number version. */
		xmlWriter->writeStartDocument();
		/* Writes a start element with name,
		* Subsequent calls to writeAttribute() will add attributes to this element.
		 here we creating a tag <persons>*/
		xmlWriter->writeStartElement("persons");
 
		/* create mapiterator to iterate through maps*/
		QMapIterator<QString, QString> i(firstname);
		QMapIterator<QString, QString> j(surname);
		QMapIterator<QString, QString> k(phoneNumber);
 
		/*this while loop generates <person> tag with attributes and CDATA in each execution.
		* currently we have 5 element in map so loop creates 5 tags.
		*/
		while (i.hasNext() && j.hasNext() && k.hasNext()) 
	    {
			i.next(); j.next();	k.next();
			/* create tag person */
			xmlWriter->writeStartElement("person");
			/*add one attribute and its value*/
			xmlWriter->writeAttribute(i.key(), i.value());
			/*add one attribute and its value*/
			xmlWriter->writeAttribute(j.key(), j.value());
			/*add one attribute and its value*/
			xmlWriter->writeAttribute(k.key(), k.value());
			/*add character data to tag person */
			xmlWriter->writeCharacters ("kamlesh");
			/*close tag person  */
			xmlWriter->writeEndElement();
 
	    } 
	    /*end tag persons*/
		xmlWriter->writeEndElement();
		/*end document */
		xmlWriter->writeEndDocument();
               delete xmlWriter;
	}
}
 
// code for destructor
GenerateXML::~GenerateXML()
{
 
}

Postconditions

The code snippet is expected to generate XML as shown below.

  <?xml version="1.0" encoding="UTF-8" ?> 
- <persons>
  <person firstname="yza" surname="bcd" number="756776">kamlesh</person> 
  <person firstname="stu" surname="vwx" number="87654">kamlesh</person> 
  <person firstname="mno" surname="pqr" number="12356">kamlesh</person> 
  <person firstname="ghi" surname="jkl" number="67890">kamlesh</person> 
  <person firstname="abc" surname="def" number="12345">kamlesh</person> 
  </persons>

External links

• QXmlStreamWriter: QXmlStreamWriter reference

Internal links

• QXmlStreamReader to parse XML in Qt

Code Example

• File:QtGenerateXML.zip will generate XML and is tested on Nokia 5800 XpressMusic.