XML实例

1. TiXmlDocumentdoc("demo.xml");
2. doc.LoadFile();

//loadthenamedfileanddumpitsstructuretoSTDOUT

voiddump_to_stdout(constchar*pFilename)

{

TiXmlDocumentdoc(pFilename);

boolloadOkay=doc.LoadFile();

if(loadOkay)

printf("n%s:n",pFilename);

dump_to_stdout(&doc);//definedlater

}

else

printf("Failedtoloadfile"%s"n",108); color:inherit; line-height:14px"> }

intmain(void)

{

dump_to_stdout("example1.xml");

return0;

读下面的文件

<?xmlversion="1.0"?>

<Hello>World</Hello>

DECLARATION

+ELEMENTHello

+TEXT[World]

voidbuild_simple_doc()

//Makexml:<?xml..><Hello>World</Hello>

TiXmlDocumentdoc;

TiXmlDeclaration*decl=newTiXmlDeclaration("1.0","","");

TiXmlElement*element=newTiXmlElement("Hello");

TiXmlText*text=newTiXmlText("World");

element->LinkEndChild(text);

doc.LinkEndChild(decl);

doc.LinkEndChild(element);

doc.SaveFile("madeByHand.xml");

}

voidwrite_simple_doc2()

//sameaswrite_simple_doc1butaddeachnode

//asearlyaspossibleintothetree.

doc.LinkEndChild(decl);

doc.LinkEndChild(element);

doc.SaveFile("madeByHand2.xml");

给定一个节点，设置它的属性也很简单：

window=newTiXmlElement("Demo");

window->SetAttribute("name","Circle");

window->SetAttribute("x",5);

window->SetAttribute("y",15);

window->SetDoubleAttribute("radius",3.14159);

//printallattributesofpElement.

//returnsthenumberofattributesprinted

intdump_attribs_to_stdout(TiXmlElement*pElement,unsignedintindent)

if(!pElement)return0;

TiXmlAttribute*pAttrib=pElement->FirstAttribute();

inti=0;

intival;

doubledval;

constchar*pIndent=getIndent(indent);

printf("n");

while(pAttrib)

printf("%s%s:value=[%s]",pIndent,pAttrib->Name(),pAttrib->Value());

if(pAttrib->QueryIntValue(&ival)==TIXML_SUCCESS)printf("int=%d",ival);

if(pAttrib->QueryDoubleValue(&dval)==TIXML_SUCCESS)printf("d=%1.1f",dval);

printf("n");

i++;

pAttrib=pAttrib->Next();

}

returni;

我们经常通过配置文件来保存程序的一些配置信息。下面给一个实例来用XML加载和保存C++对象。

#include<string>

#include<map>

usingnamespacestd;

typedefstd::map<std::string,std::string>MessageMap;

//abasicwindowabstraction-demopurposesonly

classWindowSettings

public:

intx,y,w,h;

stringname;

WindowSettings()

:x(0),y(0),w(100),h(100),name("Untitled")

}

WindowSettings(intx,inty,intw,inth,conststring&name)

this->x=x;

this->y=y;

this->w=w;

this->h=h;

this->name=name;

};

classConnectionSettings

public:

stringip;

doubletimeout;

};

classAppSettings

stringm_name;

MessageMapm_messages;

list<WindowSettings>m_windows;

ConnectionSettingsm_connection;

AppSettings(){}

voidsave(constchar*pFilename);

voidload(constchar*pFilename);

//justtoshowhowtodoit

voidsetDemoValues()

m_name="MyApp";

m_messages.clear();

m_messages["Welcome"]="Welcometo"+m_name;

m_messages["Farewell"]="Thankyouforusing"+m_name;

m_windows.clear();

m_windows.push_back(WindowSettings(15,15,400,250,"Main"));

m_connection.ip="Unknown";

m_connection.timeout=123.456;

};

AppSettingssettings;

settings.save("appsettings2.xml");

settings.load("appsettings2.xml");

同样的我们可以运行时修改配置：

//block:customiseandsavesettings

settings.m_name="HitchHikerApp";

settings.m_messages["Welcome"]="Don'tPanic";

settings.m_messages["Farewell"]="Thanksforallthefish";

settings.m_windows.push_back(WindowSettings(15,25,300,"BookFrame"));

settings.m_connection.ip="192.168.0.77";

settings.m_connection.timeout=42.0;

//block:loadsettings

AppSettingssettings;

settings.load("appsettings2.xml");

printf("%s:%sn",settings.m_name.c_str(),

settings.m_messages["Welcome"].c_str());

WindowSettings&w=settings.m_windows.front();

printf("%s:Showwindow'%s'at%d,%d(%dx%d)n",

settings.m_name.c_str(),w.name.c_str(),w.x,w.y,w.w,w.h);

printf("%s:%sn",settings.m_messages["Farewell"].c_str());

有很多方法可以保存对象的属性信息，也就是对象的状态信息。下面的实例展示如何将对象的状态编码进XML文件。

voidAppSettings::save(constchar*pFilename)

TiXmlDocumentdoc;

TiXmlElement*msg;

TiXmlComment*comment;

strings;

TiXmlElement*root=newTiXmlElement(m_name.c_str());

doc.LinkEndChild(root);

comment=newTiXmlComment();

s="Settingsfor"+m_name+"";

comment->SetValue(s.c_str());

root->LinkEndChild(comment);

//block:messages

MessageMap::iteratoriter;

TiXmlElement*msgs=newTiXmlElement("Messages");

root->LinkEndChild(msgs);

for(iter=m_messages.begin();iter!=m_messages.end();iter++)

conststring&key=(*iter).first;

conststring&value=(*iter).second;

msg=newTiXmlElement(key.c_str());

msg->LinkEndChild(newTiXmlText(value.c_str()));

msgs->LinkEndChild(msg);

//block:windows

TiXmlElement*windowsNode=newTiXmlElement("Windows");

root->LinkEndChild(windowsNode);

list<WindowSettings>::iteratoriter;

for(iter=m_windows.begin();iter!=m_windows.end();iter++)

constWindowSettings&w=*iter;

TiXmlElement*window;

window=newTiXmlElement("Window");

windowsNode->LinkEndChild(window);

window->SetAttribute("name",w.name.c_str());

window->SetAttribute("x",w.x);

window->SetAttribute("y",w.y);

window->SetAttribute("w",w.w);

window->SetAttribute("h",w.h);

//block:connection

TiXmlElement*cxn=newTiXmlElement("Connection");

root->LinkEndChild(cxn);

cxn->SetAttribute("ip",m_connection.ip.c_str());

cxn->SetDoubleAttribute("timeout",m_connection.timeout);

doc.SaveFile(pFilename);

下面的示例展示如何从XML文件中获得对象的状态信息：

voidAppSettings::load( TiXmlDocumentdoc(pFilename);

if(!doc.LoadFile())return;

TiXmlHandlehDoc(&doc);

TiXmlElement*pElem;

TiXmlHandlehRoot(0);

//block:name

pElem=hDoc.FirstChildElement().Element();

//shouldalwayshaveavalidrootbuthandlegracefullyifitdoes

if(!pElem) m_name=pElem->Value();

//savethisforlater

hRoot=TiXmlHandle(pElem);

//block:stringtable

m_messages.clear();//trashexistingtable

pElem=hRoot.FirstChild("Messages").FirstChild().Element();

for(pElem;pElem;pElem=pElem->NextSiblingElement())

constchar*pKey=pElem->Value();

constchar*pText=pElem->GetText();

if(pKey&&pText)

m_messages[pKey]=pText;

m_windows.clear();//trashexistinglist

TiXmlElement*pWindowNode=hRoot.FirstChild("Windows").FirstChild().Element();

for(pWindowNode;pWindowNode;pWindowNode=pWindowNode->NextSiblingElement())

WindowSettingsw;

constchar*pName=pWindowNode->Attribute("name");

if(pName)w.name=pName;

pWindowNode->QueryIntAttribute("x",&w.x);//Ifthisfails,originalvalueisleftas-is

pWindowNode->QueryIntAttribute("y",&w.y);

pWindowNode->QueryIntAttribute("w",&w.w);

pWindowNode->QueryIntAttribute("hh",&w.h);

m_windows.push_back(w);

pElem=hRoot.FirstChild("Connection").Element();

if(pElem)

m_connection.ip=pElem->Attribute("ip");

pElem->QueryDoubleAttribute("timeout",&m_connection.timeout);

函数dump_to_stdout如下：

#include"stdafx.h"

#include"tinyxml.h"

//----------------------------------------------------------------------

//STDOUTdumpandindentingutilityfunctions

constunsignedintNUM_INDENTS_PER_SPACE=2;

constchar*getIndent(unsignedintnumIndents)

staticconstchar*pINDENT="+";

constunsignedintLENGTH=strlen(pINDENT);

unsignedintn=numIndents*NUM_INDENTS_PER_SPACE;

if(n>LENGTH)n=LENGTH;

return&pINDENT[LENGTH-n];

//sameasgetIndentbutno"+"attheend

constchar*getIndentAlt(unsignedintnumIndents)

constchar*pINDENT="";

constunsignedintLENGTH=strlen(pINDENT);

unsignedintn=numIndents*NUM_INDENTS_PER_SPACE;

if(n>LENGTH)n=LENGTH;

return&pINDENT[LENGTH-n];

intdump_attribs_to_stdout(TiXmlElement*pElement,unsignedintindent)

TiXmlAttribute*pAttrib=pElement->FirstAttribute();

inti=0;

intival;

doubledval;

constchar*pIndent=getIndent(indent);

while(pAttrib)

printf("%s%s:value=[%s]",pAttrib->Value());

i++;

pAttrib=pAttrib->Next();

returni;

voiddump_to_stdout(TiXmlNode*pParent,unsignedintindent=0)

if(!pParent)return;

TiXmlNode*pChild;

TiXmlText*pText;

intt=pParent->Type();

printf("%s",getIndent(indent));

intnum;

switch(t)

caseTiXmlNode::TINYXML_DOCUMENT:

printf("Document");

break;

caseTiXmlNode::TINYXML_ELEMENT:

printf("Element[%s]",pParent->Value());

num=dump_attribs_to_stdout(pParent->ToElement(),indent+1);

switch(num)

case0:printf("(Noattributes)");break;

case1:printf("%s1attribute",getIndentAlt(indent));default:printf("%s%dattributes",getIndentAlt(indent),num);caseTiXmlNode::TINYXML_COMMENT:

printf("Comment:[%s]",pParent->Value());

caseTiXmlNode::TINYXML_UNKNOWN:

printf("Unknown");

caseTiXmlNode::TINYXML_TEXT:

pText=pParent->ToText();

printf("Text:[%s]",pText->Value());

caseTiXmlNode::TINYXML_DECLARATION:

printf("Declaration");

default:

for(pChild=pParent->FirstChild();pChild!=0;pChild=pChild->NextSibling())

dump_to_stdout(pChild,indent+1);

//loadthenamedfileanddumpitsstructuretoSTDOUT

boolloadOkay=doc.LoadFile();

if(loadOkay)

printf("n%s:n",pFilename);

dump_to_stdout(&doc);//definedlaterinthetutorial

如果你想在MFC中使用TinyXML，会出现这样的编译错误fatal error C1010: unexpected end of file while looking for precompiled header。因为预编译头文件通过编译stdafx.cpp生成，可以在4个实现CPP文件中引入头#include "stdafx.h"。记得放在最前面。这样就可以编译通过了。

（编辑：李大同）

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