Using QDomDocument to parse XML

Article Metadata

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Code Example

Source file: Media:QXMLDocExample.zip Media:SimpleRSSExample.zip

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Article

Created: symbianyucca (14 Jun 2010)

Last edited: hamishwillee (11 Oct 2012)

24 Oct
2010

Overview

This code example shows you how to parse well-formed XML with QDomDocument. QDomDocument is easy and strait forward way on parsing well known XML documents.

Preconditions

• Download and install the Qt SDK

QDomDocument parsing Example

XML file

<?xml version="1.0" encoding="UTF-8" ?>
<persons>
    <person id="1">
        <firstname>John</firstname>
        <surname>Doe</surname>
        <email>john.doe@example.com</email>
        <website>http://en.wikipedia.org/wiki/John_Doe</website>
    </person>
    <person id="2">
        <firstname>Jane</firstname>
        <surname>Doe</surname>
        <email>jane.doe@example.com</email>
        <website>http://en.wikipedia.org/wiki/John_Doe</website>
    </person>
    <person id="3">
        <firstname>Matti</firstname>
        <surname>Meikäläinen</surname>
        <email>matti.meikalainen@example.com</email>
        <website>http://fi.wikipedia.org/wiki/Matti_Meikäläinen</website>
    </person>
</persons>

Header file

class QXSRExample : public QMainWindow
{
    Q_OBJECT
 
public:
    QXSRExample(QWidget *parent = 0);
    ~QXSRExample();
private slots:
    void parseXML();
private:
    QPointer<QVBoxLayout> _layout;
    void setupUI();
    void addPersonsToUI(QList< QMap<QString,QString> >& persons);
};

Source file

void QXSRExample::parseXML() {
    /* We'll parse the example.xml */
    QFile* file = new QFile("C://example.xml");
    /* If we can't open it, let's show an error message. */
    if (!file->open(QIODevice::ReadOnly | QIODevice::Text)) {
        QMessageBox::critical(this,
                              "QXSRExample::parseXML",
                              "Couldn't open example.xml",
                              QMessageBox::Ok);
        return;
    }
 
    QList< QMap<QString,QString> > persons;
 
    /* QDomDocument takes any QIODevice. as well as QString buffer*/
    QDomDocument doc("mydocument"); 
    if (!doc.setContent(file)) 
    {          
    	return;      
	}      
 
    //Get the root element
    QDomElement docElem = doc.documentElement(); 
 
    // you could check the root tag name here if it matters
	QString rootTag = docElem.tagName(); // == persons
 
	// get the node's interested in, this time only caring about person's
	QDomNodeList nodeList = docElem.elementsByTagName("person");
 
	//Check each node one by one.
	for(int ii = 0;ii < nodeList.count(); ii++)
    {
		QMap<QString, QString> person;
 
		// get the current one as QDomElement
    	QDomElement el = nodeList.at(ii).toElement();
 
    	person["id"] = el.attribute("id"); // get and set the attribute ID
 
    	//get all data for the element, by looping through all child elements
		QDomNode pEntries = el.firstChild();
        while(!pEntries.isNull()) {
        	QDomElement peData = pEntries.toElement();
        	QString tagNam = peData.tagName();
 
        	if(tagNam == "firstname") { /* We've found first name. */       			
				person["firstname"] = peData.text();
        	}else if(tagNam == "surname") { /* We've found surname. */
				person["surname"] = peData.text();
        	}else if(tagNam == "email") { /* We've found email. */
				person["email"] = peData.text();
        	}else if(tagNam == "website") { /* We've found website. */
				person["website"] = peData.text();
        	}
 
        	pEntries = pEntries.nextSibling();
        }
 
        persons.append(person);
     }
 
    this->addPersonsToUI(persons);
}

Postconditions

You are able to parse the XML and display it in the UI.

Supplementary material

• You can test QDomDocument with a test application. The application is available for download at File:QXMLDocExample.zip.

• there is also simple but full RSS example available at File:SimpleRSSExample.zip

See also

QXmlStreamReader to parse XML in Qt