浅谈使用Rapidxml 库遇到的问题和分析过程(分享)

void CreateXml(){  rapidxml::xml_document<> doc;    auto nodeDecl = doc.allocate_node(rapidxml::node_declaration);  nodeDecl->append_attribute(doc.allocate_attribute("version", "1.0"));  nodeDecl->append_attribute(doc.allocate_attribute("encoding", "UTF-8"));  doc.append_node(nodeDecl);//添加xml声明    auto nodeRoot = doc.allocate_node(rapidxml::node_element, "Root");//创建一个Root节点  nodeRoot->append_node(doc.allocate_node(rapidxml::node_comment, NULL, "编程语言"));//添加一个注释内容到Root，注释没有name 所以第二个参数为NULL  auto nodeLangrage = doc.allocate_node(rapidxml::node_element, "language", "This is C language");//创建一个language节点  nodeLangrage->append_attribute(doc.allocate_attribute("name", "C"));//添加一个name属性到language  nodeRoot->append_node(nodeLangrage); //添加一个language到Root节点  nodeLangrage = doc.allocate_node(rapidxml::node_element, "language", "This is C++ language");//创建一个language节点  nodeLangrage->append_attribute(doc.allocate_attribute("name", "C++"));//添加一个name属性到language  nodeRoot->append_node(nodeLangrage); //添加一个language到Root节点  doc.append_node(nodeRoot);//添加Root节点到Document  std::string buffer;  rapidxml::print(std::back_inserter(buffer), doc, 0);  std::ofstream outFile("language.xml");  outFile << buffer;  outFile.close();}

 <?xml version="1.0" encoding="UTF-8"?> <Root>   <!--编程语言-->   <language name="C">This is C language</language>   <language name="C++">This is C++ language</language> </Root>

void MotifyXml(){  rapidxml::file<> requestFile("language.xml");//从文件加载xml  rapidxml::xml_document<> doc;  doc.parse<0>(requestFile.data());//解析xml  auto nodeRoot = doc.first_node();//获取第一个节点，也就是Root节点  auto nodeLanguage = nodeRoot->first_node("language");//获取Root下第一个language节点  nodeLanguage->first_attribute("name")->value("Motify C");//修改language节点的name属性为 Motify C  std::string buffer;  rapidxml::print(std::back_inserter(buffer), doc, 0);  std::ofstream outFile("MotifyLanguage.xml");  outFile << buffer;  outFile.close();}

 <Root>   <language name="Motify C">This is C language</language>   <language name="C++">This is C++ language</language> </Root>

template<class OutIt, class Ch>    inline OutIt print(OutIt out, const xml_node<Ch> &node, int flags = 0)   {     return internal::print_node(out, &node, flags, 0);   }

// Print node    template<class OutIt, class Ch>    inline OutIt print_node(OutIt out, const xml_node<Ch> *node, int flags, int indent)    {      // Print proper node type      switch (node->type())      {      // Document      case node_document:        out = print_children(out, node, flags, indent);        break;      // Element      case node_element:        out = print_element_node(out, node, flags, indent);        break;            // Data      case node_data:        out = print_data_node(out, node, flags, indent);        break;            // CDATA      case node_cdata:        out = print_cdata_node(out, node, flags, indent);        break;      // Declaration      case node_declaration:        out = print_declaration_node(out, node, flags, indent);        break;      // Comment      case node_comment:        out = print_comment_node(out, node, flags, indent);        break;            // Doctype      case node_doctype:        out = print_doctype_node(out, node, flags, indent);        break;      // Pi      case node_pi:        out = print_pi_node(out, node, flags, indent);        break;        // Unknown      default:        assert(0);        break;      }            // If indenting not disabled, add line break after node      if (!(flags & print_no_indenting))        *out = Ch('/n'), ++out;      // Return modified iterator      return out;    }

// Print element nodetemplate<class OutIt, class Ch>inline OutIt print_element_node(OutIt out, const xml_node<Ch> *node, int flags, int indent){  assert(node->type() == node_element);  // Print element name and attributes, if any  if (!(flags & print_no_indenting))  ...//省略部分代码    return out;}

// Printing flagsconst int print_no_indenting = 0x1;  //!< Printer flag instructing the printer to suppress indenting of XML. See print() function.

// Parsing flags  //! Parse flag instructing the parser to not create data nodes.   //! Text of first data node will still be placed in value of parent element, unless rapidxml::parse_no_element_values flag is also specified.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_no_data_nodes = 0x1;        //! Parse flag instructing the parser to not use text of first data node as a value of parent element.  //! Can be combined with other flags by use of | operator.  //! Note that child data nodes of element node take precendence over its value when printing.   //! That is, if element has one or more child data nodes <em>and</em> a value, the value will be ignored.  //! Use rapidxml::parse_no_data_nodes flag to prevent creation of data nodes if you want to manipulate data using values of elements.  //! <br><br>  //! See xml_document::parse() function.  const int parse_no_element_values = 0x2;    //! Parse flag instructing the parser to not place zero terminators after strings in the source text.  //! By default zero terminators are placed, modifying source text.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_no_string_terminators = 0x4;    //! Parse flag instructing the parser to not translate entities in the source text.  //! By default entities are translated, modifying source text.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_no_entity_translation = 0x8;    //! Parse flag instructing the parser to disable UTF-8 handling and assume plain 8 bit characters.  //! By default, UTF-8 handling is enabled.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_no_utf8 = 0x10;    //! Parse flag instructing the parser to create XML declaration node.  //! By default, declaration node is not created.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_declaration_node = 0x20;    //! Parse flag instructing the parser to create comments nodes.  //! By default, comment nodes are not created.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_comment_nodes = 0x40;    //! Parse flag instructing the parser to create DOCTYPE node.  //! By default, doctype node is not created.  //! Although W3C specification allows at most one DOCTYPE node, RapidXml will silently accept documents with more than one.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_doctype_node = 0x80;    //! Parse flag instructing the parser to create PI nodes.  //! By default, PI nodes are not created.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_pi_nodes = 0x100;    //! Parse flag instructing the parser to validate closing tag names.   //! If not set, name inside closing tag is irrelevant to the parser.  //! By default, closing tags are not validated.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_validate_closing_tags = 0x200;    //! Parse flag instructing the parser to trim all leading and trailing whitespace of data nodes.  //! By default, whitespace is not trimmed.   //! This flag does not cause the parser to modify source text.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_trim_whitespace = 0x400;  //! Parse flag instructing the parser to condense all whitespace runs of data nodes to a single space character.  //! Trimming of leading and trailing whitespace of data is controlled by rapidxml::parse_trim_whitespace flag.  //! By default, whitespace is not normalized.   //! If this flag is specified, source text will be modified.  //! Can be combined with other flags by use of | operator.  //! <br><br>  //! See xml_document::parse() function.  const int parse_normalize_whitespace = 0x800;  // Compound flags    //! Parse flags which represent default behaviour of the parser.   //! This is always equal to 0, so that all other flags can be simply ored together.  //! Normally there is no need to inconveniently disable flags by anding with their negated (~) values.  //! This also means that meaning of each flag is a <i>negation</i> of the default setting.   //! For example, if flag name is rapidxml::parse_no_utf8, it means that utf-8 is <i>enabled</i> by default,  //! and using the flag will disable it.  //! <br><br>  //! See xml_document::parse() function.  const int parse_default = 0;    //! A combination of parse flags that forbids any modifications of the source text.   //! This also results in faster parsing. However, note that the following will occur:  //! <ul>  //! <li>names and values of nodes will not be zero terminated, you have to use xml_base::name_size() and xml_base::value_size() functions to determine where name and value ends</li>  //! <li>entities will not be translated</li>  //! <li>whitespace will not be normalized</li>  //! </ul>  //! See xml_document::parse() function.  const int parse_non_destructive = parse_no_string_terminators | parse_no_entity_translation;    //! A combination of parse flags resulting in fastest possible parsing, without sacrificing important data.  //! <br><br>  //! See xml_document::parse() function.  const int parse_fastest = parse_non_destructive | parse_no_data_nodes;    //! A combination of parse flags resulting in largest amount of data being extracted.   //! This usually results in slowest parsing.  //! <br><br>  //! See xml_document::parse() function.  const int parse_full = parse_declaration_node | parse_comment_nodes | parse_doctype_node | parse_pi_nodes | parse_validate_closing_tags;

 doc.parse<0>(requestFile.data());//解析xml auto nodeRoot = doc.first_node("");//获取第一个节点，也就是Root节点 

 doc.parse<rapidxml::parse_declaration_node | rapidxml::parse_comment_nodes | rapidxml::parse_non_destructive>(requestFile.data());//解析xml auto nodeRoot = doc.first_node("Root");//获取第一个节点，也就是Root节点