Generate XML programatically in Qt

Comments

15 Sep
2009

Article Review by deepikagohil (20090915)

XMLL is "Extensible Markup Language". It is set of rules for encoding documents electronically. XML is commonly used in interchanging data over internet. XML conains tex data supported by Unicode.

The artilce presents the applicaton to generate XML programatically in Qt for Symbian. The API used in the article to acheieve this is QXmlStreamWriter. The artice contains quick overview and code for the application. Working of each function is explained and code contains comments at various places to let us understand. The article is well organized.

XML is widey used over internet. So the article has its imporance for the beginners who want to start developing applications which have use of internet.

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

Article Metadata

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Code Example

Source file: Media:QtGenerateXML.zip

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Tested with

Devices(s): Nokia 5800 XpressMusic

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Compatibility

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

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Platform Security

Signing Required: Self-Signed

Capabilities: None

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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.