Easily process XML files using the Pugixml library

Author of the article: Caspian
Source website: Ace Pilot_Caspian_Caspian NX secondary development 3000 examples, Caspian BlockUI column, C\C++-CSDN blog

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Table of contents

1 Introduction

2.Pugixml library

3. Configure the Visual Studio development environment

4.Node

5. Common node types

6. Namespace pugi  

7.xml_document loads the entire XML document structure

 8.xml_node document node

 9.xml_attribute attribute

10.Examples

1. Generate xml file

2. Read the xml file and parse it

3. Modify xml file

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1 Introduction

        Pugixml is a lightweight, simple, and fast XML parser. The Pugixml library consists of only three files: pugixml.cpp, pugixml.hpp and pugiconfig.hpp, which is very easy to use. The parsing speed is fast and XPath expressions are supported.

2.Pugixml library

        Official website download address: pugixml.org - Home

        

3. Configure the Visual Studio development environment

1. Create a project and set the "src" directory to "Additional Include Directories":

2. Add files

3. The code contains the header files pugiconfig.hpp and pugixml.hpp

#include <Windows.h>  
#include <iostream>  
#include <string>  
#include <pugiconfig.hpp> //包含头文件  
#include <pugixml.hpp>   //包含头文件
int main()
{
    
  
    std::cin.get();
    return 0;
}

4.Node

       The root of the tree is the document itself, which corresponds to the C++ type  xml_document . Document subnode, corresponding to C++ type  xml_node . Nodes have different types, corresponding to C++ types xml_attribute

5. Common node types

1. Document Node (  node_document ) - This is the root of the tree and consists of multiple child nodes. This node corresponds to  xml_document a class; note that it is   a subclass of , so the entire node interface is also available xml_document . xml_node
2. Element/Tag Node (  node_element ) - This is the most common node type and represents an XML element. An element node has a name, a collection of attributes, and a collection of child nodes (both of which may be empty). This property is a simple name/value pair.
3. Plain character data nodes (  node_pcdata ) represent plain text in XML. PCDATA nodes have values, but no names or child nodes/properties. Note that plain character data is not part of the element node, but has its own node; for example, an element node can have multiple child PCDATA nodes.

6. Namespacepugi  

        All pugixml classes and functions are in a namespace  pugi ; you must use explicit name qualification (i.e.  pugi::xml_node ), or   access   the relevant symbols via directives (i.e. using pugi::xml_node; or  ).using namespace pugi;using

7.xml_document loads the entire XML document structure

        xml_document is the owner of the entire document structure; destroying the document destroys the entire tree. The xml_document interface consists of a load function, a save function and the entire xml_node interface, allowing document inspection and/or modification.

 8.xml_node document node

        xml_node is a handle to a document node; it can point to any node in the document, including the document itself. All types of nodes have a common interface. Note that this is just the xml_node handle to the actual node, not the node itself - you can have multiple xml_node handles pointing to the same underlying object. Destroying the xml_node handle does not destroy the node, nor does it remove it from the tree.

        xml_node has a special type value called empty node or empty node. It does not correspond to any node in any document and is therefore similar to a null pointer. However, all operations are defined on empty nodes; typically operations do nothing and return empty nodes/properties or empty strings as their results. This is useful for chaining calls; i.e., you can get the node's grandparent like this: node.parent().parent() ; if the node is an empty node or has no parent, the first parent() call returns an empty node ;Then the second parent() call also returns a null node, so you don't have to check for errors twice. You can test whether a handle is null via an implicit boolean conversion: if (node) { …​ } or if (!node) { …​ }.

 9.xml_attribute attribute

        xml_attribute is a handle to an XML attribute; it has the same semantics as xml_node , i.e. there can be multiple xml_attribute handles pointing to the same underlying object, and there is a special null attribute value that is propagated to the function result.

10.Examples

Example 1. Generate xml file

#include <Windows.h>  
#include <iostream>
#include <fstream>  
#include <string>  
#include <pugiconfig.hpp> //包含头文件  
#include <pugixml.hpp>   //包含头文件

using namespace std;
using namespace pugi;

int main()
{
	// 创建一个XML文档对象  
	xml_document doc;

	// 添加根节点  
	xml_node root = doc.append_child("fruits");

	// 添加子节点  
	xml_node apple = root.append_child("fruit");
	apple.append_attribute("name").set_value("苹果");
	apple.append_attribute("color").set_value("红色");
	apple.append_attribute("taste").set_value("甜");

	xml_node banana = root.append_child("fruit");
	banana.append_attribute("name").set_value("香蕉");
	banana.append_attribute("color").set_value("黄色");
	banana.append_attribute("taste").set_value("甜");

	// 将XML内容写入文件  
	ofstream file("fruits.xml");
	doc.save(file);
	file.close();

	std::cin.get();
	return 0;
}

Example 2. Read xml file and parse it

#include <Windows.h>  
#include <iostream>
#include <fstream>  
#include <string>  
#include <pugiconfig.hpp> //包含头文件  
#include <pugixml.hpp>   //包含头文件

using namespace std;
using namespace pugi;

int main()
{
	// 打开XML文件  
	ifstream file("fruits.xml");

	// 加载XML文档  
	xml_document doc;
	doc.load(file);

	// 获取根节点  
	xml_node root = doc.child("fruits");

	// 遍历子节点  
	for (xml_node fruit = root.first_child(); fruit; fruit = fruit.next_sibling()) {
		// 获取属性值  
		string name = fruit.attribute("name").as_string();
		string color = fruit.attribute("color").as_string();
		string taste = fruit.attribute("taste").as_string();

		// 输出属性值  
		cout << "Name: " << name << endl;
		cout << "Color: " << color << endl;
		cout << "Taste: " << taste << endl;
	}

	std::cin.get();
	return 0;
}

Example 3. Modify xml file

Purpose: Change apples to cyan and less sweet

#include <Windows.h>  
#include <iostream>
#include <fstream>  
#include <string>  
#include <pugiconfig.hpp> //包含头文件  
#include <pugixml.hpp>   //包含头文件

using namespace std;
using namespace pugi;

int main()
{
    // 打开XML文件  
    ifstream file("fruits.xml");

    // 加载XML文档  
    xml_document doc;
    doc.load(file);

    // 获取根节点  
    xml_node root = doc.child("fruits");

    // 遍历子节点  
    for (xml_node fruit = root.first_child(); fruit; fruit = fruit.next_sibling()) {
        // 获取属性值  
        string name = fruit.attribute("name").as_string();

        // 如果该子节点表示的是苹果  
        if (name == "苹果") {
            // 修改属性值  
            fruit.attribute("color").set_value("青色");
            fruit.attribute("taste").set_value("不甜");
            break; // 只修改第一个匹配的节点，退出循环  
        }
    }

    // 将修改后的XML内容写入文件  
    ofstream outfile("fruits.xml");
    doc.save(outfile);
    outfile.close();

	std::cin.get();
	return 0;
}