C++ xml 解析器

　　C++的xml解析器有很多，这个知乎回答里有一个列表:https://www.zhihu.com/question/32046606

　　下面使用其中的RapidXml试试。

　　官方地址： https://link.zhihu.com/?target=http%3A//rapidxml.sourceforge.net/

　　Manual地址：http://rapidxml.sourceforge.net/manual.html

　　这里有个例子：https://www.cnblogs.com/lancidie/p/3304089.html

　　上面代码是在ubuntun下是编译不过的，我作了小的更改：

　　编译环境：Ubuntu 16.04   、 gcc version 5.4.0

　　下载了上面rapidxml 1.13版本，这个版本在此环境下，仍需要打一个补丁，其实就是在rapidxml_print.hpp开头加了以下几行声明，放在类内部开始即可。

         template<class OutIt, class Ch> inline OutIt print_children(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_element_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_data_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_cdata_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_declaration_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_comment_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_doctype_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);
         template<class OutIt, class Ch> inline OutIt print_pi_node(OutIt out, const xml_node<Ch> *node, int flags, int indent);

　　整个代码如下：

 #include "rapidxml/rapidxml.hpp"
 #include "rapidxml/rapidxml_print.hpp"
 #include "rapidxml/rapidxml_utils.hpp"

 #include <string>
 #include <iostream>
 #include <fstream>

 using namespace rapidxml;
 using namespace std;

 void WriteXml1()
 {
     xml_document<> doc;
     xml_node<>* rot = doc.allocate_node(rapidxml::node_pi,doc.allocate_string("xml version='1.0' encoding='utf-8'"));
     doc.append_node(rot);
     xml_node<>* node =   doc.allocate_node(node_element,"config",NULL);
     xml_node<>* color =   doc.allocate_node(node_element,"color",NULL);
     doc.append_node(node);
     node->append_node(color);
     color->append_node(doc.allocate_node(node_element,"red","0.1"));
     color->append_node(doc.allocate_node(node_element,"green","0.1"));
     color->append_node(doc.allocate_node(node_element,"blue","0.1"));
     color->append_node(doc.allocate_node(node_element,"alpha","1.0"));

     xml_node<>* size =   doc.allocate_node(node_element,"size",NULL);
     size->append_node(doc.allocate_node(node_element,"x",""));
     size->append_node(doc.allocate_node(node_element,"y",""));
     node->append_node(size);

     xml_node<>* mode = doc.allocate_node(rapidxml::node_element,"mode","screen mode");
     mode->append_attribute(doc.allocate_attribute("fullscreen","false"));
     node->append_node(mode);

     std::string text;
     rapidxml::print(std::back_inserter(text), doc, );

     std::cout<<text<<std::endl;

     std::ofstream out("config.xml");
     out << doc;
 }

 void WriteXml2()
 {
     xml_document<> doc; //是解析器
     char a[] = "<top>"//如果单独传, 就不能加上xml的头部信息，
             //否则会报错
             "<name>tangqiang</name>"
             "<age>22</age>"
             "</top>";
     char* p = a;
     doc.parse<>(p);

     xml_node<>* node = doc.first_node();//去顶级结点
     cout << (node->name())<< endl;
     node = node->first_node();
     while (node) {
         cout << node->name() << node->value() << endl;//name() value()返回的字符串不会去掉首尾的空白字符
         node = node->next_sibling();
     }

     ofstream out("test.xml");//ofstream 默认时，如果文件存在则会覆盖原来的内容，不存在则会新建
     out << doc;//doc 这样输出时在目标文件中不会有xml 头信息---<?xml version='1.0' encoding='utf-8' >
     out.close();
 }

 void ReadXml()
 {
     file<> fdoc("config.xml");
     std::cout<<fdoc.data()<<std::endl;
     xml_document<>   doc;
     doc.parse<>(fdoc.data());

     std::cout<<doc.name()<<std::endl;

     //! 获取根节点
     xml_node<>* root = doc.first_node();
     std::cout<<root->name()<<std::endl;

     //! 获取根节点第一个节点
     xml_node<>* node1 = root->first_node();
     std::cout<<node1->name()<<std::endl;

     xml_node<>* node11 = node1->first_node();
     std::cout<<node11->name()<<std::endl;
     std::cout<<node11->value()<<std::endl;

     //! 添加之后再次保存
     //需要说明的是rapidxml明显有一个bug
     //那就是append_node(doc.allocate_node(node_element,"h","0"));的时候并不考虑该对象是否存在!
     xml_node<>* size = root->first_node("size");
     size->append_node(doc.allocate_node(node_element,"w",""));
     size->append_node(doc.allocate_node(node_element,"h",""));

     std::string text;
     rapidxml::print(std::back_inserter(text),doc,);

     std::cout<<text<<std::endl;

     std::ofstream out("config.xml");
     out << doc;
 }

 void DeleteXml()
 {
     file<> fdoc("config.xml");
     xml_document<> doc;
     doc.parse<>(fdoc.data());

     std::string text;
     rapidxml::print(std::back_inserter(text), doc, );
     std::cout<<text<<std::endl;

     xml_node<>* root = doc.first_node();

     xml_node<>* sec = root->first_node();

     root->remove_node(sec); //移除根节点下的sec结点(包括该结点下所有结点)
     text="删除一个节点\r\n";
     rapidxml::print(std::back_inserter(text), doc, );
     std::cout<<text<<std::endl;

     root->remove_all_nodes(); //移除根节点下所有结点
     text="删除所有节点\r\n";
     rapidxml::print(std::back_inserter(text), doc, );
     std::cout<<text<<std::endl;

     std::ofstream out("test.xml");
     out<<doc;
 }

 void EditXml()
 {
     file<> fdoc("config.xml");
     std::cout<<fdoc.data()<<std::endl;
     xml_document<> doc;
     doc.parse<>(fdoc.data());

     std::cout<<doc.name()<<std::endl;

     //! 获取根节点
     xml_node<>* root = doc.first_node();
     xml_node<>* delnode = root->first_node("color");
     root->remove_node(delnode);//先删除address节点
     //
     xml_node<>* lnode = root->first_node("size");//找到post节点
     xml_node<>* mynode=doc.allocate_node(node_element,"address","河北");
     root->insert_node(lnode,mynode);

     std::string text;
     rapidxml::print(std::back_inserter(text),doc,);

     std::cout<<text<<std::endl;

     std::ofstream out("version.xml");
     out << doc;
 }

 void TravelsalXml()
 {
     file<> fdoc("config.xml");
     //std::cout<<fdoc.data()<<std::endl;
     xml_document<> doc;
     doc.parse<>(fdoc.data());

     //std::cout<<doc.name()<<std::endl;

     //! 获取根节点
     xml_node<>* root = doc.first_node();

     for(rapidxml::xml_node<char> * node = root->first_node();
         node != NULL;
         node = node->next_sibling())
     {
         std::cout<<(node->name())<<"  "<<(node->value())<<endl;
     }

     std::cout<<"travesal from size node"<<std::endl;
     for(rapidxml::xml_node<char> * node = root->first_node("size");
         node != NULL;
         node = node->next_sibling())
     {
         std::cout<<(node->name())<<"  "<<(node->value())<<endl;
     }
 }

 void TravelsalAttrXml()
 {
     file<> fdoc("config.xml");
     xml_document<> doc;
     doc.parse<>(fdoc.data());

     //! 获取根节点
     xml_node<>* root = doc.first_node();
     xml_node<>* subroot = root->first_node("mode");

     for(rapidxml::xml_attribute<char> * attr = subroot->first_attribute("fullscreen");
         attr != NULL;
         attr = attr->next_attribute())
     {
         //char * value = attr->value();

         cout<<(attr->name())<<" "<<(attr->value())<<endl;
     }
 }

 int main()
 {
     //WriteXml1();
     //WriteXml2();
     //ReadXml();
     //DeleteXml();
     //EditXml();

     //TravelsalXml();
     TravelsalAttrXml();

     return ;
 }

　　总结：以上代码演示了写XML、读XML、删除某一个节点、遍历所有的节点、遍历所有的属性。

　　RapidXml可以说，使用起来非常方便。