（4）rapidxml的详解及使用

    RapidXml是指 XML DOM解析工具包，是一个快速的读写xml文件的库文件（hpp）。

    （1）创建XML文件

#include <iostream>
#include <string>
#include <fstream>
#include "string.h"
#include "rapidxml.hpp"
#include "rapidxml_print.hpp"
#include "rapidxml_utils.hpp"

static const int buf_len = 2048;
static char buf[buf_len] = { 0 };

void createXML(const char * file_name)
{
  // 1.DOM
  rapidxml::xml_document<> doc;

  // 2.node_declaration
  rapidxml::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);

  // 3.node_pi
  rapidxml::xml_node<>* dec = doc.allocate_node(rapidxml::node_pi,doc.allocate_string("xml version=\"1.0\" encoding=\"utf-8\""));
  doc.append_node(dec);

  // 4.node_element
  rapidxml::xml_node<>* root = doc.allocate_node(rapidxml::node_element, "root");
  doc.append_node(root);

  // 5.node_comment
  rapidxml::xml_node<>* comment = doc.allocate_node(rapidxml::node_comment, 0, "这是一个注释节点");
  root->append_node(comment);

  rapidxml::xml_node<>* students = doc.allocate_node(rapidxml::node_element, "students");

  // 6.node_data
  rapidxml::xml_node<>* one_student = doc.allocate_node(rapidxml::node_element, "student");
  rapidxml::xml_node<>* name = doc.allocate_node(rapidxml::node_data,"node_name","11");
  one_student->append_node(name);
  students->append_node(one_student);

  // 7.node_element with value
  rapidxml::xml_node<>* two_student = doc.allocate_node(rapidxml::node_element, "student","22");
  students->append_node(two_student);

  // 8.set attribute
  rapidxml::xml_node<>* three_student = doc.allocate_node(rapidxml::node_element,"student","33");
  students->append_node(three_student);
  three_student->append_attribute(doc.allocate_attribute("course", doc.allocate_string(buf)));
  three_student->append_attribute(doc.allocate_attribute("score","98"));

  // 9.node_element without value
  rapidxml::xml_node<>* four_student = doc.allocate_node(rapidxml::node_element,"student");
  students->append_node(four_student);

  // 10.node_cdata
  rapidxml::xml_node<>* five_student = doc.allocate_node(rapidxml::node_cdata,"student","55");
  students->append_node(five_student);

  // 11.node_cdata
  rapidxml::xml_node<>* six_student = doc.allocate_node(rapidxml::node_pi,"student","66");
  students->append_node(six_student);

  // 12.node_cdata
  rapidxml::xml_node<>* seven_student = doc.allocate_node(rapidxml::node_doctype,"student","77");
  students->append_node(seven_student);
  root->append_node(students);

  // 13.输出DOM到命令行
  std::cout<<doc;

  // 14.输出DOM到文件
  std::ofstream outfile(file_name, std::ios::out);
  if (outfile)
  {
    char *end = rapidxml::print(buf, doc, 0);
    *end = 0;
    outfile << buf;
    outfile.close();
  }
}

int main()
{
  const char *file_name = "rapid.xml";
  createXML(file_name);
  return 0;
}

<?xml version="1.0" encoding="utf-8"?>
<?xml version="1.0" encoding="utf-8" ?>
<root>
        <!--这是一个注释节点-->
        <students>
                <student>11</student>
                <student>22</student>
                <student course="" score="98">33</student>
                <student/>
                <![CDATA[55]]>
                <?student 66?>
                <!DOCTYPE 77>
        </students>
</root>

    （2）读取XML文件

//rapidxml_utils.hpp
file类
data()  返回 char* 的xml文本内容
size()  返回 unsigned int的文本数据长度
定义：rapidxml::file<0> valName(“filepath”);
//rapidxml.hpp
xml_document类
parse(Ch *text);将文本数据解析为DOM tree
clear();清空DOM tree
定义：rapidxml::xml_document<0> doc;
const int parse_default = 0;
const int parse_full = parse_declaration_node | parse_comment_nodes | parse_doctype_node | parse_pi_nodes | parse_validate_closing_tags

#include <iostream>
#include <string>
#include <fstream>
#include "unistd.h"
#include "string.h"
#include "rapidxml.hpp"
#include "rapidxml_print.hpp"
#include "rapidxml_utils.hpp"

static const int buf_len = 2048;
static char buf[buf_len] = { 0 };

//利用rapidxml::file读取配置文件
void readXMLByFile(const char *file_name)
{
    try
    {
      // 1.清空缓冲区
      memset(buf,0,buf_len);
      // 2.拼接绝对路径
      std::string strXml = "/home/sunjimeng/test/";
      strXml.append(file_name);
      // 3.用file文件读入缓冲区
      rapidxml::file<> fdoc(strXml.c_str());
      // 4.打印从文件中读取的内容
      std::cout<<fdoc.data();
      // 5.解析获取DOM实例
      rapidxml::xml_document<> doc;
      doc.parse<0>(fdoc.data());
    }catch(rapidxml::parse_error e)
    {
      std::cout<<e.what()<<std::endl;
      return;
    }
}
void readXMLByStream(const char *file_name)
{
  try
  {
    // 1.清空缓冲区
    memset(buf,0,buf_len);
    // 2.判断文件是否存在
    if(access(file_name,F_OK) == -1)
        std::cout<<"xml file "<<file_name<<"is not exits!"<<std::endl;
    // 3.实例化文件读取流
    std::ifstream infile(file_name, std::ios::in);
    if(!infile)
    {
        std::cout<<"file stream instance error!"<<std::endl;
        return;
    }
    // 4.读取文件内容到缓冲区
    infile.read(buf, buf_len);
    // 5.输出文件内容
    std::cout<<buf<<std::endl;
    // 6.实例化DOM
    rapidxml::xml_document<> doc;
    doc.parse<0>(buf);
  }catch(rapidxml::parse_error e)
  {
    std::cout<<e.what()<<std::endl;
    return;      
  }
}
int main()
{
  const char *file_name = "rapid.xml";
  readXMLByFile(file_name);
  readXMLByStream(file_name);
  return 0;
}

    （3）修改及删除（接着上文）

//rapidxml.hpp
xml_node类
1）node_type type() const; 获取结点类型 获取的类型是枚举的
2）Ch* name() const; 获取结点名
3）std::size_t name_size() const; 获取结点名长度
4）Ch* value() const; 获取结点值
5）std::size_t value_size() const; 获取结点值长度
6）xml_node* first_node(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取DOM Tree第一个子结点的指针
第一个参数为节点名，如果给定第一个参数为”a”,则该函数寻找结点名为a的第一个子结点；第二个参数为结点名长度
7）xml_node* last_node(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取DOM Tree最后一个子结点的指针
参数含义同上
8)xml_attribute* first_attribute(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取结点的第一个属性指针
9）xml_attribute* next_attribute(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取结点的下一个属性指针
10）xml_attribute* last_attribute(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const;获取结点的最后一个属性指针
11）xml_node* previous_sibling(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const;获取上一个同级结点的指针
12）xml_node* next_sibling(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取下一个同级结点的指针
13）xml_attribute* first_attribute(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取第一个同级结点的指针
14）xml_attribute* last_attribute(const Ch *name=0, std::size_t name_size=0, bool case_sensitive=true) const; 获取最后一个同级结点的指针
15）void insert_node(xml_node< Ch > *where, xml_node< Ch > *child);在第一个参数指向的结点之前，插入一个结点
xml_attribute类
1)xml_attribute *previous_attribute(const Ch *name = 0, std::size_t name_size = 0, bool case_sensitive = true) const;获取前一个属性
2）xml_attribute *next_attribute(const Ch *name = 0, std::size_t name_size = 0, bool case_sensitive = true) const；获取后一个属性

#include <iostream>
#include <string>
#include <fstream>
#include "unistd.h"
#include "string.h"
#include "rapidxml.hpp"
#include "rapidxml_print.hpp"
#include "rapidxml_utils.hpp"

static const int buf_len = 2048;
static char buf[buf_len] = { 0 };

void parseXML(const char * file_name)
{
  memset(buf,0,buf_len);
  try
  {
    std::ifstream infile(file_name, std::ios::in);
    if (!infile)
    {
      return;
    }
    infile.read(buf, buf_len);
    std::cout << buf << std::endl;

    rapidxml::xml_document<> doc;
    doc.parse<0>(buf);
    // 取得根节点
    rapidxml::xml_node<> *root = doc.first_node("root");
    // 遍历students的子节点
    int flag = 0;
    for (rapidxml::xml_node<> * node = root->first_node("students")->first_node(); node; node = node->next_sibling())
    {
      if(node->first_node() != NULL)
        std::cout<<"name :"<<node->name()<<" value : "<<node->value()<<std::endl;
      else
        std::cout<<"name :"<<node->name()<<" has no value!"<<std::endl;
      for(rapidxml::xml_attribute<> * attribute = node->first_attribute(); attribute; attribute = attribute->next_attribute())
        std::cout<<"      attribute name = "<<attribute->name()<<" attribute value = "<<attribute->value()<<std::endl;
    }
  } catch(rapidxml::parse_error e)
  {
    std::cout<<e.what()<<std::endl;
  }
}
void modifyXML(const char * file_name)
{
  memset(buf,0,buf_len);
  //用file解析DOM时必须是绝对路径
  std::string strXml = "/home/sunjimeng/test/";
  strXml.append(file_name);
  rapidxml::file<> fdoc(strXml.c_str());
  //打印读取的文件
  //std::cout<<fdoc.data();
  rapidxml::xml_document<> doc;
  doc.parse<0>(fdoc.data());
  //取得根节点
  rapidxml::xml_node<> *root = doc.first_node("root");
  rapidxml::xml_node<> *students = root->first_node("students");
  if(students != NULL)
    std::cout<<"student is not null"<<std::endl;
  else
    return;
  //删除最后一个元素
  if(students->last_node() != NULL)
    students->remove_last_node();
  //删除第一个元素
  if(students->first_node() != NULL)
    students->remove_first_node();
  rapidxml::xml_node<> *ptrNode = students->first_node();

  int size = 0;
  while(ptrNode)
  {
    size++;
    //删除所有属性
    ptrNode->remove_all_attributes();
    ptrNode = ptrNode->next_sibling();
  }
  std::cout<<"size = "<<size<<std::endl;
  std::string text;
  rapidxml::print(std::back_inserter(text),doc,0);
  std::cout<<text<<std::endl;
  std::ofstream out(file_name);
  out<<doc;
}
int main()
{
  const char *file_name = "rapid.xml";
  modifyXML(file_name);
  parseXML(file_name);
  return 0;
}

student is not null
size = 1
<root>
        <students>
                <student>33</student>
        </students>
</root>


<root>
        <students>
                <student>33</student>
        </students>
</root>


name :student value : 33