Development/Tutorials/Programming Tutorial KDE 4/How to write an XML parser: Difference between revisions
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reader.setContentHandler( handler ); | reader.setContentHandler( handler ); | ||
reader.parse( source ); | reader.parse( source ); | ||
} | |||
</highlightSyntax> | |||
Next file is parser.h: | |||
<highlightSyntax language="cpp"> | |||
/* | |||
parser.h - demonstration of a parser in C++ | |||
*/ | |||
#ifndef PARSER_H | |||
#define PARSER_H | |||
#include <qstring.h> | |||
#include <QtXml/QXmlDefaultHandler> | |||
#include <QtXml/QXmlAttributes> | |||
class Parser : public QXmlDefaultHandler | |||
{ | |||
public: | |||
Parser(); | |||
/** given by the framework from qxml. Called when parsing the xml-document starts. */ | |||
bool startDocument(); | |||
/** given by the framework from qxml. Called when the reader occurs an open tag (e.g. \<b\> ) */ | |||
bool startElement( const QString&, const QString&, const QString& qName, const QXmlAttributes& att ); | |||
}; | |||
#endif | |||
</highlightSyntax> | |||
Next file is parser.cpp: | |||
<highlightSyntax language="cpp"> | |||
/* | |||
parser.cpp - demonstration of a parser in C++ | |||
*/ | |||
#include "parser.h" | |||
#include <kdebug.h> | |||
Parser::Parser() | |||
{ | |||
} | |||
bool Parser::startDocument() | |||
{ | |||
kDebug() << "Searching document for tags" << endl; | |||
return true; | |||
} | |||
bool Parser::startElement( const QString&, const QString&, const QString& qName, const QXmlAttributes& att ) | |||
{ | |||
kDebug() << "Found Element " << qName << endl; | |||
return true; | |||
} | |||
</highlightSyntax> | |||
<highlightSyntax language="cpp"> | |||
/* | |||
dom.cpp | |||
A demonstration how to use the dom parsing framework. | |||
Prints the first subnode of an html file, i.e. typically "head" or "body". | |||
compile it like this: | |||
g++ -I. -I/opt/kde3/include -I/usr/lib/qt3/include dom.cpp -L/opt/kde3/lib -L/usr/lib/qt3/lib -lqt-mt -lkdeui | |||
*/ | |||
#include <qdom.h> | |||
#include <qfile.h> | |||
#include <kdebug.h> | |||
int main() | |||
{ | |||
QDomDocument doc( "myDocument" ); | |||
QFile qf("hello.htm"); | |||
doc.setContent( &qf ); | |||
QDomElement docElement = doc.documentElement(); | |||
QDomNode node; | |||
node = docElement.firstChild(); | |||
kdDebug() << node.nodeName() << endl; | |||
} | } | ||
</highlightSyntax> | </highlightSyntax> |
Revision as of 20:46, 31 August 2006
A parser is used to distinguish between formal language and bulk data of a given grammar. See en.wikipedia.org/wiki/Parser if in doubt. There are two ways to write a parser: to split up the content of a file into an object as known from object-oriented programming or to trigger a function everytime a reader occurs a given syntax tag. In the following code, a function is triggered for every time an html tag is found in a file. The first file is hello.cpp: <highlightSyntax language="cpp"> /* hello.cpp compile it with g++ -I. -I/home/kde-devel/kde/include -I/home/kde-devel/qt-unstable/include/Qt -I/home/kde-devel/qt-unstable/include -I/home/kde-devel/qt-unstable/include/QtXml parser.h parser.cpp hello.cpp -L/home/kde-devel/kde/lib -L/home/kde-devel/qt-unstable/lib -lQtCore_debug -lQtXml_debug -lkdeui
- /
- include <qstring.h>
- include <QXmlInputSource>
- include <qfile.h>
- include <parser.h>
int main() {
Parser* handler=new Parser(); QXmlInputSource* source=new QXmlInputSource(new QFile("hello.htm")); QXmlSimpleReader reader; reader.setContentHandler( handler ); reader.parse( source );
} </highlightSyntax> Next file is parser.h: <highlightSyntax language="cpp"> /*
parser.h - demonstration of a parser in C++
- /
- ifndef PARSER_H
- define PARSER_H
- include <qstring.h>
- include <QtXml/QXmlDefaultHandler>
- include <QtXml/QXmlAttributes>
class Parser : public QXmlDefaultHandler { public:
Parser();
/** given by the framework from qxml. Called when parsing the xml-document starts. */ bool startDocument();
/** given by the framework from qxml. Called when the reader occurs an open tag (e.g. \<b\> ) */ bool startElement( const QString&, const QString&, const QString& qName, const QXmlAttributes& att );
};
- endif
</highlightSyntax>
Next file is parser.cpp: <highlightSyntax language="cpp"> /*
parser.cpp - demonstration of a parser in C++
- /
- include "parser.h"
- include <kdebug.h>
Parser::Parser() { } bool Parser::startDocument() { kDebug() << "Searching document for tags" << endl; return true; } bool Parser::startElement( const QString&, const QString&, const QString& qName, const QXmlAttributes& att ) { kDebug() << "Found Element " << qName << endl; return true; }
</highlightSyntax>
<highlightSyntax language="cpp"> /*
dom.cpp A demonstration how to use the dom parsing framework. Prints the first subnode of an html file, i.e. typically "head" or "body". compile it like this: g++ -I. -I/opt/kde3/include -I/usr/lib/qt3/include dom.cpp -L/opt/kde3/lib -L/usr/lib/qt3/lib -lqt-mt -lkdeui
- /
- include <qdom.h>
- include <qfile.h>
- include <kdebug.h>
int main() {
QDomDocument doc( "myDocument" ); QFile qf("hello.htm"); doc.setContent( &qf ); QDomElement docElement = doc.documentElement(); QDomNode node; node = docElement.firstChild(); kdDebug() << node.nodeName() << endl;
} </highlightSyntax>