problem in reading xml file with SAX parser.

[Niamita]

Hi all

I am reading a xml file but i am not successing in reading it. My code for reading file is


Xmlhandler::Xmlhandler(QTableWidget *table)
{
tablewidget = table;
table_item = 0;
}

bool Xmlhandler::startElement(const QString &, const QString &, const QString &qName,const QXmlAttributes &attributes)
{
if (qName == "statement"){
tablewidget->insertRow(1);

if(qName == "Condition")
{
QString str_id = attributes.value("text");
qDebug()<<str_id;
table_item = new QTableWidgetItem();

}
else if(qName == "action")
{
QString str_id = attributes.value("text");
qDebug()<<str_id;
table_item = new QTableWidgetItem();

}
else if(qName == "text")
currenttext.clear();
}
return true;
}

bool Xmlhandler::characters(const QString &str)
{
currenttext += str;
return true;
}

bool Xmlhandler::endElement(const QString &,const QString &,const QString &qName)
{
if(qName == "statement"){
if (qName == "Condition") {
if (qName == "page") {
table_item->setText(currenttext);
tablewidget->setItem(0, 0, table_item);
}
}
if (qName == "action") {
if (qName == "page") {
table_item->setText(currenttext);
tablewidget->setItem(0, 1, table_item);
}
}
}
return true;
}

bool Xmlhandler::fatalError(const QXmlParseException &exception)
{
QMessageBox::warning(0, QObject::tr("SAX Handler"),QObject::tr("Parse error at line %1, column "
"%2:\n%3.").arg(exception.lineNumber()).arg(exception.column Number()).arg(exception.message()));
return false;
}

and my xml file is like this-

<?xml version="1.0" encoding="UTF-8"?>
<statement>
<Condition id="1">
<text></text>
</Condition>
<action id="1">
<text></text>
</action>
</statement>

<statement>
<Condition id="2">
<text>Analog Input Equals to 1 END</text>
</Condition>
<action id="2">
<text>Digital Output Equals to ON END</text>
</action>
</statement>

i am trying to read xml and display it in a table.

Please guide me , i am doing this since three days but i am not getting desired result.

Thank you.

[wysota]

What is wrong exactly? Saying "it doesn't work" doesn't provide any hints as to what is wrong. One thing might be that you don't have a root element in your xml.

[Niamita]

ya i also think so , so that i am now generating xml with rrot element through DOM parser, but when i create file then it is ok but when i want to add new entries it is not getting append to the root node in xml file.
My code for this is


const int Indent = 4;
static QDomDocument doc;
static QDomElement root;
QDomElement statement, action_node, condition_node;
root = doc.createElement("root");
QFile *file = new QFile("E:/new.txt");
if(!file->exists())
{
file->open(QIODevice::WriteOnly);
doc.appendChild(root);
}
else
{
file->open(QIODevice::Append);
statement = doc.createElement("statement");
condition_node = doc.createElement("condition");
action_node = doc.createElement("action");
QDomText condition_text = doc.createTextNode(condition_text_edit->toPlainText());
QDomText action_text = doc.createTextNode(action_text_edit->toPlainText());
root.appendChild(statement);
statement.appendChild(condition_node);
statement.appendChild(action_node);
condition_node.appendChild(condition_text);
action_node.appendChild(action_text);
}
if(file->error())
qDebug()<<file->errorString();

QTextStream out(file);
doc.save(out, Indent);

what i am doing wrong now.

[wysota]

You can't append to the file like that. You need to replace the contents of the file and not append to it.

[Niamita]

Please be more elaborated, it is possible to give some sample code.

[wysota]

If you have a document and you modify it, you need to save the whole document to the file overwriting the old version of the document. XML doesn't work in an "additive" manner. It's a matter of understanding how XML works. If you open the file in append mode, you will get two documents one after the other instead of having the updated document only.

[Niamita]

So what i have to do now , do i have to create temproryfile.

[wysota]

You have to read the original document from the file, update it with new entries and save it back again. No temporary files are needed.

[Niamita]

Can you please give me some sample code. I have confused a lot.

[wysota]

QFile file("some.xml");
file.open(QFile::ReadWrite);
QDomDocument doc;
doc.setContent(&file);
QDomElement root = doc.documentElement();
QDomElement newOne = root.createElement("elem");
root.appendChild(newOne);
file.seek(0);
QTextStream stream(&file);
doc.save(stream); // or file.write(doc.toByteArray());

[Niamita]

I tried as you suggested but now i am facing a problem when i close the program and then write on the file , it write nothing on the file but it is working fine when the program is running once. I am getting error that "Calling appendChild() on a null node does nothing. " what is wrong with this.

My code is:


const int Indent = 4;
static QDomDocument doc;
static QDomElement root,root1;
QDomElement statement, action_node, condition_node;
root = doc.createElement("root");
QFile *file = new QFile("E:/new.txt");
if(!file->exists())
{
file->open(QIODevice::WriteOnly);
doc.appendChild(root);
}
else
{
file->open(QFile::ReadWrite);
root1 = doc.documentElement();
statement = doc.createElement("statement");
condition_node = doc.createElement("condition");
action_node = doc.createElement("action");
QDomText condition_text = doc.createTextNode(condition_text_edit->toPlainText());
QDomText action_text = doc.createTextNode(action_text_edit->toPlainText());
statement.appendChild(condition_node);
statement.appendChild(action_node);
condition_node.appendChild(condition_text);
action_node.appendChild(action_text);
root1.appendChild(statement);
file->seek(0);
}
QTextStream out(file);
doc.save(out, Indent)

It is solved. Actually i am not setting contents of document.
doc.setContent(file);

[Niamita]

Hi

How to update a textnode data in xml through QDomElement.
I have following code


static QDomDocument doc;
static QDomElement root,root1;
QDomElement statement, action_node, condition_node;
QDomText id_text;
root = doc.createElement("root");
QFile *file = new QFile("E:/new.txt");
if(!file->exists())
{
file->open(QIODevice::WriteOnly);
QDomElement id = doc.createElement("id");
id_text = doc.createTextNode("0");
root.appendChild(id);
id.appendChild(id_text);
doc.appendChild(root);
}
else
{
file->open(QFile::ReadWrite);
doc.setContent(file);
root1 = doc.documentElement();
QDomElement node = root1.firstChildElement("id");
QString string_data = node.text();
int a = string_data.toInt();
qDebug()<<string_data;
string_data.clear();
id_text = doc.createTextNode("Qt"); // Here i want to write Qt but it is getting write 0Qt on the textnode.
node.appendChild(id_text);
statement = doc.createElement("statement");
condition_node = doc.createElement("condition");
action_node = doc.createElement("action");
QDomText condition_text = doc.createTextNode(condition_text_edit->toPlainText());
QDomText action_text = doc.createTextNode(action_text_edit->toPlainText());
statement.setAttribute("id", i);
statement.appendChild(condition_node);
statement.appendChild(action_node);
condition_node.appendChild(condition_text);
action_node.appendChild(action_text);
root1.appendChild(statement);

// QString str = statement.attribute("id");
// qDebug()<<str.toInt();
file->seek(0);

}
QTextStream out(file);
doc.save(out, Indent);
So i want to update the textnode value while it is getting append in previous value.
Please anyone help me.
Waiting for response.