XML的创建和读取

news/2024/5/5 2:42:03/文章来源:https://blog.csdn.net/lmy347771232/article/details/128044766

rapidxml是一个快速的xml库，由C++模板实现的高效率xml解析库，同时也是boost库的property_tree的内置解析库。

当使用rapidxml时，只需要把rapidxml.hpp 、 rapidxml_print.hpp 和
rapidxml_utils.hpp 三个文件拷贝到你的工程目录下，就可以了。

一、xml的创建

1.xml创建并打印

代码执行时发现的错误：
bool Create(std::string filename)
{//DOMrapidxml::xml_document<>doc;2.node_declarationrapidxml::xml_node<>* declaration = doc.allocate_node(rapidxml::node_declaration);declaration->append_attribute(doc.allocate_attribute("version", "1.0"));declaration->append_attribute(doc.allocate_attribute("encoding", "utf-8"));doc.append_node(declaration);下面代码出问题：有如下图片显示的错误std::cout << doc;// 无法编译通过，为什么？std::ofstream outfile(filename, std::ios::out);if (outfile){下面代码出问题：有如下图片显示的错误char* end = rapidxml::print(buff, doc, 0);//无法编译通过//std::cout << buff << std::endl;return true;}return false;}

创建时遇到的问题：
1.打印DOM的一个节点到缓冲区失败
2.打印DOM的一个节点到buff失败
在这里插入图片描述
解决办法：
在用这些函数的函数前加个此函数的声明：

下面的注释都是后加的，解决了找不到的问题。
/*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);*/template<class OutIt, class Ch>inline OutIt print_node(OutIt out, const xml_node<Ch> *node, int flags, int indent){// Print proper node typeswitch (node->type()){// Documentcase node_document:out = print_children(out, node, flags, indent);break;// Elementcase node_element:out = print_element_node(out, node, flags, indent);break;// Datacase node_data:out = print_data_node(out, node, flags, indent);break;// CDATAcase node_cdata:out = print_cdata_node(out, node, flags, indent);break;// Declarationcase node_declaration:out = print_declaration_node(out, node, flags, indent);break;// Commentcase node_comment:out = print_comment_node(out, node, flags, indent);break;// Doctypecase node_doctype:out = print_doctype_node(out, node, flags, indent);break;// Picase node_pi:out = print_pi_node(out, node, flags, indent);break;// Unknowndefault:assert(0);break;}// If indenting not disabled, add line break after nodeif (!(flags & print_no_indenting))*out = Ch('\n'), ++out;// Return modified iteratorreturn out;}

2.创建自己的数据输出到xml文件

步骤：
1.创建各个节点，并设置属性，注意控制节点之间的父子关系；
2.创建输出流ofstream,用rapidxml::print方法将doc数据输入到buff中;
3.用outfile将buff数据导入到文件中。

bool Create(std::string filename)
{//DOMstd:: vector<std::string>::iterator it;rapidxml::xml_document<>doc;std::vector<std::string>tmp;tmp.push_back("Count");tmp.push_back("Step");tmp.push_back("Record");tmp.push_back("Record");std::vector<std::string>tmp1;tmp1.push_back("10");tmp1.push_back("100");tmp1.push_back("1000");tmp1.push_back("10000");2.node_declarationrapidxml::xml_node<>* declaration = doc.allocate_node(rapidxml::node_declaration);declaration->append_attribute(doc.allocate_attribute("version", "1.0"));declaration->append_attribute(doc.allocate_attribute("encoding", "utf-8"));doc.append_node(declaration);rapidxml::xml_node<>* Info = doc.allocate_node(rapidxml::node_element, "Info");doc.append_node(Info);rapidxml::xml_node<>* Settings = doc.allocate_node(rapidxml::node_element, "Settings");Info->append_node(Settings);std::vector<std::string>::iterator it1 = tmp1.begin();for (it = tmp.begin(); it != tmp.end(); it++) {rapidxml::xml_node<>* Count = doc.allocate_node(rapidxml::node_element,it->c_str());Count->append_attribute(doc.allocate_attribute("value", it1->c_str()));Settings->append_node(Count);it1++;}//analysis->append_node()rapidxml::xml_node<>* InstanceInfo = doc.allocate_node(rapidxml::node_element,"InstanceInfo");Info->append_node(InstanceInfo);for (int i = 0; i < 3; i++){rapidxml::xml_node<>* Instance = doc.allocate_node(rapidxml::node_element,"Instance");InstanceInfo->append_node(Instance);Instance->append_attribute(doc.allocate_attribute("id","1"));Instance->append_attribute(doc.allocate_attribute("name", "xxx"));Instance->append_attribute(doc.allocate_attribute("fun", "sin"));for (int j = 0; j < 2; j++){rapidxml::xml_node<>* Parameter = doc.allocate_node(rapidxml::node_element, "Parameter");Instance->append_node(Parameter);Parameter->append_attribute(doc.allocate_attribute("name", "own"));Parameter->append_attribute(doc.allocate_attribute("init", "1"));}}std::cout << doc;// error  为什么？std::ofstream outfile(filename, std::ios::out);if (outfile){char* end = rapidxml::print(buff, doc, 0);*end = 0;outfile << buff; //outfile.close();}return true;}
int main(){const char* file_name = "xxx.xml";bool res = Create(file_name);if (!res){return -1;}return 0;
}

成功输出数据到文件中
在这里插入图片描述

二、读取xml格式到buff

/*这几个文件都要在项目文件夹中，才可以调用库文件*/
#include "rapidxml_print.hpp"
#include "rapidxml_utils.hpp"
//#include "rapidxml_iterators.hpp"
//#include "rapidxml_iterators.hpp"
using namespace rapidxml;
static const int buff_len = 2048;
static char buff[buff_len] = { 0 };
bool Read()
{memset(buff, 0,buff_len);std::string filename = "demo.xml";//实例化文件读取流std::ifstream infile(filename, std::ios::in);if (!infile){std::cout << "file stream instance error!" << std::endl;return false;}//从流中读到buffinfile.read(buff, buff_len);std::cout << buff << std::endl;
}int main()
{bool res = Read();if (!res){return -1;}return 0;
}