QT XML文档的解析 QXmlStreamReader， DOM，SAX 三种解析方法 简单示例

0. xml文档如下

<?xml version="1.0"?>
<bookindex>
    <entry term="sidebearings">
        <page>10</page>
        <page>34-35</page>
        <page>307-308</page>
    </entry>
    <entry term="subtraction">
        <entry term="of pictures">
            <page>115</page>
            <page>244</page>
        </entry>
        <entry term="of vectors">
            <page>9</page>
        </entry>
    </entry>
</bookindex>

1. 用QXmlStreamReader 解析

使用QT时需要添加xml模块， 修改工程文件.pro，QT+=xml

//#include "widget.h"
#include <QApplication>
#include <QtGui>
#include <qxmlstream.h>
#include <iostream>
#include <QDebug>

QXmlStreamReader reader;
bool readFile(const QString &fileName);
void readBookindexElement();  //解析含有0或以上<entry>元素的 <bookindex> ... </bookindex>
void readEntryElement();      //解析含有0或以上<page>元素的<entry> ... </entry>
void skipUnknowElement();     //跳过不认识的元素
void readPageElement();       //解析一个<page> ... </page> 元素

bool readFile(const QString &fileName)
{
    QFile file(fileName);
    if( !file.open(QFile::ReadOnly | QFile::Text) )
    {
        std::cerr << "Error: Cannot read file" << qPrintable(fileName)
                  << ": " << qPrintable(file.errorString()) << std::endl;
        return false;
    }

    reader.setDevice(&file);
    reader.readNext();
    while( !reader.atEnd() )
    {
        if( reader.isStartElement() )
        {
            qDebug() << "reader.name: " << reader.name();
            if( reader.name() == "bookindex" )
            {
                qDebug() << "start element: bookindex";
                readBookindexElement();
                break;
            }
            else
            {
                qDebug() << "not a right start element";
                reader.raiseError(QObject::tr("not a right start element"));
            }
        }
        else
            reader.readNext();
    }
    file.close();
}

void readBookindexElement()
{
    reader.readNext();
    while( !reader.atEnd() )
    {
        if(reader.isEndElement())
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
        {
            if( reader.name() == "entry" )
            {
                readEntryElement();
            }
            else
                skipUnknowElement();
        }
        else
            reader.readNext();
    }
}

void readEntryElement()
{
    //qDebug() << "readEntryElement";
    reader.readNext();
    while(!reader.atEnd())
    {
        if(reader.isEndElement())
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
        {
            if( reader.name() == "entry" )
                readEntryElement();
            else if( reader.name() == "page" )
                readPageElement();
            else
                skipUnknowElement();
        }
        else
            reader.readNext();
    }
}

void skipUnknowElement()
{
    //qDebug() << "skipUnknowElement";
    reader.readNext();
    while(!reader.atEnd())
    {
        if( reader.isEndElement() )
        {
            reader.readNext();
            break;
        }

        if(reader.isStartElement())
            skipUnknowElement();
        else
            reader.readNext();
    }
}

void readPageElement()
{
    //qDebug() << "readPageElement";
    QString page = reader.readElementText();
    if( reader.isEndElement() )
        reader.readNext();
    qDebug() << "page: " << page;
}

int main(int argc, char *argv[])
{
    readFile("77.xml");

    return 0;
}

2. 用DOM方式解析

使用QT时需要添加xml模块， 修改工程文件.pro，QT+=xml

#include "widget.h"
#include <QApplication>
#include <QtGui>
#include <QDomElement>
#include <QDebug>
#include <iostream>

bool readFile(const QString &fileName);
void parseBookindexElement(const QDomElement &element);
void parseEntryElement(const QDomElement &element);
void parsePageElement(const QDomElement &element);

bool readFile(const QString &fileName)
{
    //qDebug() << "readFile";
    QFile file(fileName);
    if( !file.open(QFile::ReadOnly | QFile::Text) )
    {
        std::cerr << "Error: cannot read file" << qPrintable(fileName)
                  <<": " << qPrintable(file.errorString()) << std::endl;
        return false;
    }

    QString errorStr;
    int errorLine;
    int errorColumn;

    QDomDocument doc;
    if( !doc.setContent(&file, false, &errorStr, &errorLine, &errorColumn) )
    {
        std::cerr << "Error: Parse error at line " << errorLine <<","
                  << "column " << errorColumn << ","
                  << qPrintable(errorStr) << std::endl;
        return false;
    }

    QDomElement root = doc.documentElement();
    if( root.tagName() != "bookindex" )
    {
        std::cerr << "Error: root element is not right" << std::endl;
        return false;
    }
    parseBookindexElement(root);
    return true;

}

void parseBookindexElement(const QDomElement &element)
{
    //qDebug() << "parseBookindexElement";
    QDomNode child = element.firstChild();
    while(!child.isNull())
    {
        if( child.toElement().tagName() == "entry" )
            parseEntryElement(child.toElement());
        child = child.nextSibling();
    }
}

void parseEntryElement(const QDomElement &element)
{
    //qDebug() << "parseEntryElement";
    QDomNode child = element.firstChild();
    while(!child.isNull())
    {
        if( child.toElement().tagName() == "entry" )
            parseEntryElement(child.toElement());
        else if( child.toElement().tagName() == "page" )
            parsePageElement(child.toElement());

        child = child.nextSibling();
    }
}

void parsePageElement(const QDomElement &element)
{
    //qDebug() << "parsePageElement";
    QString page = element.text();
    qDebug() << "page: " << page;
}

int main(int argc, char *argv[])
{
    readFile("77.xml");

    return 0;
}