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.columnNumber()).arg(exception.message()));
    return false;
}

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.columnNumber()).arg(exception.message()));
    return false;
}

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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);

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);

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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());

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());

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[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)

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)

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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);

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);

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So i want to update the textnode value while it is getting append in previous value.
Please anyone help me.
Waiting for response.