Parse an Xml file with Qt

Bogdan112

Hey,
I am trying to parse an xml file and to save all the output in a QString vector.
I don't know why but it add same elements like : "\n", "\n " and same blank space:
Here is the code:

 QFile* file = new QFile("new_ex4.xml");
    if (!file->open(QIODevice::ReadOnly | QIODevice::Text))
    {
        QMessageBox::information(0, "error", file->errorString());
         return;
    }
    QVector<QString> vector;
    QXmlStreamReader xml(file);
    QXmlStreamReader::TokenType token;
    while(!xml.atEnd() && !xml.hasError())
    {
        /* Read next element.*/
        token = xml.readNext();
        /* If token is just StartDocument, we'll go to next.*/
        if(token == QXmlStreamReader::StartDocument)
            continue;

     if(token == QXmlStreamReader::Characters)
            vector.push_back(xml.text().toString());
     
     continue;
    }

And the xml file looks like this :

<?xml version="1.0" encoding="UTF-8" ?>
<test>
    <Page1>
        <name1>stringHere</name1>
        <name2>stringHere</name2>
        <name3>stringHere</name3>
        <name4>stringHere</name4>
    </Page1>
    <Page2>
        <Val1>10.256</Val1>
        <Val2>101.2</Val2>
        <Val3>101.2</Val3>
        <Val4>101.2</Val4>
    </Page2>
    <Page3>
        <Val1>10.256</Val1>
        <Val2>101.2</Val2>
        <Val3>101.2</Val3>
        <Val4>101.2</Val4>
    </Page3>
    <Page4>
        <Val1>10.256</Val1>
        <Val2>101.2</Val2>
        <Val3>101.2</Val3>
        <Val4>101.2</Val4>
    </Page4>
    <Page5>
        <Val1>10.256</Val1>
        <Val2>101.2</Val2>
        <Val3>101.2</Val3>
        <Val4>101.2</Val4>
    </Page5>
</test>

kshegunov

You're half way there. QXmlStreamReader is in fact a glorified tokenizer, it's not really a parser. You need to do the parsing yourself. So what you get is expected - you receive the character tokens that are between the tags.

Bogdan112

But if i receive only the character between tags, why are saved in QVector new line("\n") and spceses(" ")?

mrjj

@Bogdan112

Hi
I think its due to the use of
QXmlStreamReader::Characters.

If you do something like

void readXML( ) {


  QString fileName = "e:/test.xml";

  QFile file (fileName);
  if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
    QMessageBox::critical(0, "QXSRExample::ReadXMLFile", "Couldn't open xml file", QMessageBox::Ok);
    return;
  }

  /* QXmlStreamReader takes any QIODevice. */
  QXmlStreamReader xml(&file);
  /* We'll parse the XML until we reach end of it.*/
  while(!xml.atEnd() && !xml.hasError()) {
    /* Read next element.*/
    QXmlStreamReader::TokenType token = xml.readNext();
    /* If token is just StartDocument, we'll go to next.*/
    if(token == QXmlStreamReader::StartDocument)
      continue;

    /* If token is StartElement, we'll see if we can read it.*/
    if(token == QXmlStreamReader::StartElement) {
     qDebug() << "#" << xml.name();
    }
  }
  /* Error handling. */
  if(xml.hasError())
    QMessageBox::critical(0, "parseXML", xml.errorString(), QMessageBox::Ok);

  //resets its internal state to the initial state.
  xml.clear();
}

Then it shows

# "test"
# "Page1"
# "name1"
# "name2"
# "name3"
# "name4"
# "Page2"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page3"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page4"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page5"
# "Val1"
# "Val2"
# "Val3"
# "Val4"

http://qt.shoutwiki.com/wiki/QXmlStreamReader_to_parse_XML_in_Qt

kshegunov

@Bogdan112 said in Parse an Xml file with Qt:

But if i receive only the character between tags, why are saved in QVector new line("\n") and spceses(" ")?

That's my point - there are whitespaces between the tags (not inside them). E.g.

<Page1>\n        <name1>

Bogdan112

@mrjj said in Parse an Xml file with Qt:

@Bogdan112

Hi
I think its due to the use of
QXmlStreamReader::Characters.

If you do something like

void readXML( ) {


  QString fileName = "e:/test.xml";

  QFile file (fileName);
  if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
    QMessageBox::critical(0, "QXSRExample::ReadXMLFile", "Couldn't open xml file", QMessageBox::Ok);
    return;
  }

  /* QXmlStreamReader takes any QIODevice. */
  QXmlStreamReader xml(&file);
  /* We'll parse the XML until we reach end of it.*/
  while(!xml.atEnd() && !xml.hasError()) {
    /* Read next element.*/
    QXmlStreamReader::TokenType token = xml.readNext();
    /* If token is just StartDocument, we'll go to next.*/
    if(token == QXmlStreamReader::StartDocument)
      continue;

    /* If token is StartElement, we'll see if we can read it.*/
    if(token == QXmlStreamReader::StartElement) {
     qDebug() << "#" << xml.name();
    }
  }
  /* Error handling. */
  if(xml.hasError())
    QMessageBox::critical(0, "parseXML", xml.errorString(), QMessageBox::Ok);

  //resets its internal state to the initial state.
  xml.clear();
}

Then it shows

# "test"
# "Page1"
# "name1"
# "name2"
# "name3"
# "name4"
# "Page2"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page3"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page4"
# "Val1"
# "Val2"
# "Val3"
# "Val4"
# "Page5"
# "Val1"
# "Val2"
# "Val3"
# "Val4"

http://qt.shoutwiki.com/wiki/QXmlStreamReader_to_parse_XML_in_Qt

Thank you. That solved my problem.