How to read a simple xml file.

[bod]

Hi,
First of all I must say "I am new to qt programming and also xml".
I need to parse an xml file and read the file names. That's all I want to do.
But I couldn't find any code example of reading simply an xml file. Anybody can help me please?

[mcosta]

To parse an XML file the simpler Qt way is to use QXmlStreamReader. See Qt Docs for examples.

[bod]

What do you mean by Qt docs.
I looked at Qt assistant and looked at QXmlStreamReader also. But these donot include a sample code.
Could you give me a link please?

[mcosta]

Search "QXmlStream Bookmarks Example" in Qt Assistant

[bod]

I looked at that example. Do I need to implement those xbelhandler classes?
Do I need to write classses to read just a simple file??

[aamer4yu]

Just have a look at QDomDocument, QDomElement., and QDomElement::text(). and QDomDocument::setContent. This might be sufficient for u

u can also refer to simple DOM Model in Qt Demos

[mcosta]

You can use directly QXmlStreamReader in your code.

Simple code

QFile file(fileName);
   file.open(QIODevice::ReadOnly);
 
   QXmlStreamReader xml(&file);
   while (!xml.atEnd()) 
   {
         xml.readNext();
         ... // do processing
   }
   if (xml.hasError()) 
   {
         ... // do error handling
   }
   file.close();

QFile file(fileName);
   file.open(QIODevice::ReadOnly);

   QXmlStreamReader xml(&file);
   while (!xml.atEnd()) 
   {
         xml.readNext();
         ... // do processing
   }
   if (xml.hasError()) 
   {
         ... // do error handling
   }
   file.close();

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[bod]

How can i reach the strings after reading?
I want to see, what it read.
So I will understand how this reader runs better.

[coderCPP1981]

This code may help u............

#ifndef CONTACT_H
#define CONTACT_H
 
#include<QtCore/QString>
 
class QDomElement;
class QDomDocument;
class QString;
 
class Contact
{
public:
    QString name,eMail,phone;
 
    Contact( QString iName = "", QString iPhone = "", QString iEMail = "" );
    Contact( const QDomElement &e );
 
};
 
#endif

#ifndef CONTACT_H
#define CONTACT_H

#include<QtCore/QString>

class QDomElement;
class QDomDocument;
class QString;

class Contact
{
public:
    QString name,eMail,phone;
		
    Contact( QString iName = "", QString iPhone = "", QString iEMail = "" );
    Contact( const QDomElement &e );

};

#endif

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//contact.cpp
 
#include"contact.h"
 
#include <qapplication.h>
#include <QtXml/QDomNode>
 
#include <QtCore/QDir>
#include <QtCore/QFile>
#include <QtCore/QIODevice>
#include <QDebug>
#include <QtXml/QDomDocument>
 
 
 
 
Contact::Contact( QString iName, QString iPhone, QString iEMail )
{
	name = iName;
	phone = iPhone;
	eMail = iEMail;
}
 
QDomElement ContactToNode(QDomDocument &d, const Contact &c )
{
   QDomElement cn = d.createElement( "contact" );
 
   cn.setAttribute( "NAME", c.name );
   cn.setAttribute( "PHONE", c.phone );
   cn.setAttribute( "EMAIL", c.eMail );
 
   return cn;
}
 
 
int main( int argc, char **argv )
{
 
  QApplication a( argc, argv );
  QDomDocument doc("AdBookML");
  QDomElement root = doc.createElement( "adbook" );
  doc.appendChild(root);
 
  Contact c;
 
  c.name = "AAAA";
  c.eMail = "AAAA@gmail.com";
  c.phone = "+91-32233223";
 
  root.appendChild(ContactToNode(doc,c));
 
 QFile file("test.xml");
  if( !file.open( QIODevice::WriteOnly ) )
  return -1;
 
  QTextStream ts( &file );
  ts << doc.toString();
 
  file.close();
 
 
  c.name = "BBBBB";
  c.eMail = "BBBB@gmail.com";
  c.phone = "+91-3233443440";
 
  root.appendChild( ContactToNode( doc, c ) );
if( !file.open( QIODevice::WriteOnly  ) )
  return -1;
 
 
  ts << doc.toString();
 
  c.name = "CCCCC";
  c.eMail = "maassy@gmail.com";
  c.phone = "+91-98232388";
 
  root.appendChild( ContactToNode( doc, c ) );
if( !file.open( QIODevice::WriteOnly ) )
  return -1;
 
 
  ts << doc.toString();
 
 file.close();
 
if( !file.open(QIODevice::ReadOnly ))
  return -1;
if( !doc.setContent( &file ) )
{
  file.close();
  return -2;
}
 root = doc.documentElement();
if( root.tagName() != "adbook" )
  return -3;
QDomNode n = root.firstChild();
while( !n.isNull() )
{
  QDomElement e = n.toElement();
  if( !e.isNull() )
  {
    if( e.tagName() == "contact" )
    {
      Contact c ;
 
      c.name = e.attribute( "NAME","" );
      c.phone = e.attribute( "PHONE","" );
      c.eMail = e.attribute( "EMAIL","" );
 
      qDebug()<<c.name;
      qDebug()<<c.phone;
      qDebug()<<c.eMail;
 
    }
  }
 
  n = n.nextSibling();
}
  return 0;
}

//contact.cpp

#include"contact.h"

#include <qapplication.h>
#include <QtXml/QDomNode>

#include <QtCore/QDir>
#include <QtCore/QFile>
#include <QtCore/QIODevice>
#include <QDebug>
#include <QtXml/QDomDocument>




Contact::Contact( QString iName, QString iPhone, QString iEMail )
{
	name = iName;
	phone = iPhone;
	eMail = iEMail;
}

QDomElement ContactToNode(QDomDocument &d, const Contact &c )
{
   QDomElement cn = d.createElement( "contact" );

   cn.setAttribute( "NAME", c.name );
   cn.setAttribute( "PHONE", c.phone );
   cn.setAttribute( "EMAIL", c.eMail );

   return cn;
}


int main( int argc, char **argv )
{

  QApplication a( argc, argv );
  QDomDocument doc("AdBookML");
  QDomElement root = doc.createElement( "adbook" );
  doc.appendChild(root);

  Contact c;

  c.name = "AAAA";
  c.eMail = "AAAA@gmail.com";
  c.phone = "+91-32233223";

  root.appendChild(ContactToNode(doc,c));

 QFile file("test.xml");
  if( !file.open( QIODevice::WriteOnly ) )
  return -1;

  QTextStream ts( &file );
  ts << doc.toString();

  file.close();


  c.name = "BBBBB";
  c.eMail = "BBBB@gmail.com";
  c.phone = "+91-3233443440";

  root.appendChild( ContactToNode( doc, c ) );
if( !file.open( QIODevice::WriteOnly  ) )
  return -1;

  
  ts << doc.toString();

  c.name = "CCCCC";
  c.eMail = "maassy@gmail.com";
  c.phone = "+91-98232388";

  root.appendChild( ContactToNode( doc, c ) );
if( !file.open( QIODevice::WriteOnly ) )
  return -1;

  
  ts << doc.toString();

 file.close();

if( !file.open(QIODevice::ReadOnly ))
  return -1;
if( !doc.setContent( &file ) )
{
  file.close();
  return -2;
}
 root = doc.documentElement();
if( root.tagName() != "adbook" )
  return -3;
QDomNode n = root.firstChild();
while( !n.isNull() )
{
  QDomElement e = n.toElement();
  if( !e.isNull() )
  {
    if( e.tagName() == "contact" )
    {
      Contact c ;

      c.name = e.attribute( "NAME","" );
      c.phone = e.attribute( "PHONE","" );
      c.eMail = e.attribute( "EMAIL","" );

      qDebug()<<c.name;
      qDebug()<<c.phone;
      qDebug()<<c.eMail;
     
    }
  }

  n = n.nextSibling();
}
  return 0;
}

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Thanks

[bod]

If I didnot understand wrong, the code above first create an xml file then reads it.
Am I right?

Edit: And also what is the difference between QDomElement and QDomNode?
What are they beneficial For?

[cyberboy]

The QDomElement class represents one element in the DOM tree and the QDomNode class is the base class for all the nodes in a DOM tree.

[bod]

What is base class?

[bod]

QFile file("xmldenemev2.xbel");
QXmlStreamReader xml(&file); 
QDomDocument doc("mydocument");
 
	if (!file.open(QIODevice::ReadOnly))
         return;
 
     if (!(doc.setContent(&file))) {
 ui.textEdit->setText("Fail in set Content");
         file.close();
         return;
     }
     file.close();
 
	ui.textEdit->setText("SetContent is ok");
	 // print out the element names of all elements that are direct children
     // of the outermost element.
     QDomElement docElem = doc.documentElement();
 
     QDomNode n = docElem.firstChild();
     while(!n.isNull()) {
         QDomElement e = n.toElement(); // try to convert the node to an element.
         if(!e.isNull()) {
			 ui.textEdit->setText("aGirdi");
			 ui.textEdit->setText( e.tagName()); // the node really is an element.
         }
         n = n.nextSibling();
     }

QFile file("xmldenemev2.xbel");
QXmlStreamReader xml(&file); 
QDomDocument doc("mydocument");
	
	if (!file.open(QIODevice::ReadOnly))
         return;
	
     if (!(doc.setContent(&file))) {
 ui.textEdit->setText("Fail in set Content");
         file.close();
         return;
     }
     file.close();

	ui.textEdit->setText("SetContent is ok");
	 // print out the element names of all elements that are direct children
     // of the outermost element.
     QDomElement docElem = doc.documentElement();

     QDomNode n = docElem.firstChild();
     while(!n.isNull()) {
         QDomElement e = n.toElement(); // try to convert the node to an element.
         if(!e.isNull()) {
			 ui.textEdit->setText("aGirdi");
			 ui.textEdit->setText( e.tagName()); // the node really is an element.
         }
         n = n.nextSibling();
     }

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Here is my code. But there is a mistake.It shouldn't enter the second "if". But it does.why "doc.setContent(&file)" returns false??

[mcosta]

As Qt Documentation says QDomDocument::setContent returns FALSE when the file isn't successfully parsed.

Probably there is an error in XML file. Can you post it?