xml write with only space or empty issue

[Narthan]

Hello all,

i am trying write xml file using Qdom
sample of xml file will be lke this
<?xml version='1.0'?>
<xml>
<Config>
<test>
<tag1>edit1</tag1>
<tag2>5996</tag2>
</test>
</Config>
</xml>

code sample:

        QByteArray xmlData(file->readAll());
        QDomDocument doc("config");
        doc.setContent(xmlData);
        QDomElement root = doc.firstChildElement("xml");
        QDomElement parent = root.firstChildElement("Config");
        QDomElement parent1 = parent.firstChildElement("test");
        QDomElement hostname = parent1.firstChildElement("tag1");
        hostname.firstChild().setNodeValue(ui->tag1_lineEdit->text());
        QDomElement username = parent1.firstChildElement("tag2");
        username.firstChild().setNodeValue(ui->tag2_lineEdit->text());

if tag1_lineEdit contains only space (" ") or empty ("") then xml file will be look
<?xml version='1.0'?>
<xml>
<Config>
<test>
<tag1/>
<tag2>5996</tag2>
</test>
</Config>
</xml>
again i am not able write anything in that tag from lineedit, can someone give me solution, how to write space or empty text,

[Ratzz]

Hi,
<tag1/> indicates that it is empty

<tag1/> is same as <tag1></tag1>

http://stackoverflow.com/questions/7238254/xml-what-is-this-null-or-empty-element

[Narthan]

@Ratzz Thank you for your reply, but again i am not able to write in the tag.,
For example based on save button i am saving xml file, once i entered only space to line edit, then i enter save button, it will be a empty tag(<tag1/>) in xml file, afterward again i enetered some value to lineedit and entered save button , on that time it is not updating in empty tag,

[VRonin]

from http://doc.qt.io/qt-5/qdomdocument.html

"Text nodes consisting only of whitespace are stripped and won't appear in the QDomDocument. If this behavior is not desired, one can use the setContent() overload that allows a QXmlReader to be supplied."

[Paul Colby]

It works for me (just replacing your lineEdit with plain text for testing...

QByteArray xmlData("<?xml version='1.0'?><xml><Config><test><tag1>edit1"
                   "</tag1><tag2>5996</tag2></test></Config></xml>");
QDomDocument doc("config");
doc.setContent(xmlData);
QDomElement root = doc.firstChildElement("xml");
QDomElement parent = root.firstChildElement("Config");
QDomElement parent1 = parent.firstChildElement("test");
QDomElement hostname = parent1.firstChildElement("tag1");
hostname.firstChild().setNodeValue(" "); // One space.
QDomElement username = parent1.firstChildElement("tag2");
username.firstChild().setNodeValue(""); // Empty string.
qDebug() << doc.toString();

"<?xml version='1.0'?>\n<xml>\n <Config>\n  <test>\n   <tag1> </tag1>\n   <tag2></tag2>\n  </test>\n </Config>\n</xml>\n"

How are you printing the document? And what version of Qt are you using?

Cheers.

[Paul Colby]

@VRonin said:

from http://doc.qt.io/qt-5/qdomdocument.html

"Text nodes consisting only of whitespace are stripped and won't appear in the QDomDocument. If this behavior is not desired, one can use the setContent() overload that allows a QXmlReader to be supplied."

Oh, so its problem with QDomDocument::setContent, eg:

QByteArray xmlData("<?xml version='1.0'?><xml><Config><test><tag1>edit1"
                   "</tag1><tag2>5996</tag2></test></Config></xml>");
QDomDocument doc("config");
doc.setContent(xmlData);
QDomElement root = doc.firstChildElement("xml");
QDomElement parent = root.firstChildElement("Config");
QDomElement parent1 = parent.firstChildElement("test");
QDomElement hostname = parent1.firstChildElement("tag1");
hostname.firstChild().setNodeValue(" "); // One space.
QDomElement username = parent1.firstChildElement("tag2");
username.firstChild().setNodeValue(""); // Empty string.
qDebug() << doc.toString();

QDomDocument doc2;
doc2.setContent(doc.toString());
qDebug() << doc2.toString();

Output:

"<?xml version='1.0'?>\n<xml>\n <Config>\n  <test>\n   <tag1> </tag1>\n   <tag2></tag2>\n  </test>\n </Config>\n</xml>\n"
"<?xml version='1.0'?>\n<xml>\n <Config>\n  <test>\n   <tag1/>\n   <tag2/>\n  </test>\n </Config>\n</xml>\n"

So the empty space is added correctly, even written to string correctly (doc). It just disappears when its parsed back in again (doc2).

Cheers.

[Narthan]

@Paul-Colby i am opening xml file as you mentioned
first time when i pressed save button it will show
<?xml version='1.0'?>
<xml>
<tag1> </tag1> // two spaces from line edit
</xml>

second time when i presses save button it will show

<?xml version='1.0'?>
<xml>
<tag1/> // some data in lineedit
</xml>

third time when i presses save button it will show

<?xml version='1.0'?>
<xml>
<tag1/> // some data in lineedit
</xml>

i am using Qt 4.8.7, i am opening xml file , see the result