使用C ++从xml文件中读取一行 [英] Read a line from xml file using C++

问题描述

我的XML档案包含：

<软件包>
xmlMetadata
< / Package>

我正在搜索此文件中的标签，并且此标签的开始和结束标签之间的文本必须在控制台上打印。在这种情况下，我想要在控制台上打印xmlMetadata。类似地，它应该在文件中进一步打印并且如果它遇到另一个<软件包>标签。

I am searching for a tag in this file and the text between the starting and closing tags of this has to be printed on console. i.e. in this case I want xmlMetadata to be printed on the console. Similarly it should go further in the file and print again if it encounters another < Package > tag in the same file.

这是我的代码，但它正在打印整个文件的内容：

Here is my code but it is printing the contents of the whole file:

{
    string line="< Package >";
    ifstream myfile (xmlFileName); //xmlFileName is xml file in which search is to done
    if (myfile.is_open())
    {
    while ( myfile.good() )
    {
      getline (myfile,line);
      std::cout<<line<< endl;
    }
    myfile.close();
    }
    else cout << "Unable to open file"; 
}

显示在我整个xml下面：

Displaying below my whole xml:

< ? xml version="1.0" ? >
< fileStructure >
< Main_Package >
   File_Navigate
< /Main_Package >
< Dependency_Details >

< Dependency >
   < Package >
      xmlMetadata
   < /Package >
   < Header >
      xmlMetadata.h
   < /Header >
   < Header_path >
      C:\Dependency\xmlMetadata\xmlMetadata.h
   < /Header_path >
   < Implementation >
      xmlMetadata.cpp
   < /Implementation >
   < Implementation_path >
      C:\Dependency\xmlMetadata\xmlMetadata.cpp
   < /Implementation_path >
< /Dependency >

< Dependency >
   < Package >
      xmlMetadata1
   < /Package >
   < Header >
      xmlMetadata1.h
   < /Header >
   < Header_path >
      C:\Dependency\xmlMetadata\xmlMetadata1.h
   < /Header_path >
   < Implementation >
      xmlMetadata1.cpp
   < /Implementation >
   < Implementation_path >
      C:\Dependency\xmlMetadata\xmlMetadata1.cpp
   < /Implementation_path >
< /Dependency >

< /Dependency_Details >
< /fileStructure >

推荐答案

这不是你应该解析XML文件的方式，但由于您不想使用解析器库，此代码可能会让您入门。

This is not the way you should parse an XML file, but since you don't want to use a parser library this code might get you started.

文件： demo.xml

<? xml version="1.0" ?>
<fileStructure>
<Main_Package>
   File_Navigate
</Main_Package>
<Dependency_Details>

<Dependency>
   <Package>
      xmlMetadata
   </Package>
   <Header>
      xmlMetadata.h
   </Header>
   <Header_path>
      C:\Dependency\xmlMetadata\xmlMetadata.h
   </Header_path>
   <Implementation>
      xmlMetadata.cpp
   </Implementation>
   <Implementation_path>
      C:\Dependency\xmlMetadata\xmlMetadata.cpp
   </Implementation_path>
</Dependency>

<Dependency>
   <Package>
      xmlMetadata1
   </Package>
   <Header>
      xmlMetadata1.h
   </Header>
   <Header_path>
      C:\Dependency\xmlMetadata\xmlMetadata1.h
   </Header_path>
   <Implementation>
      xmlMetadata1.cpp
   </Implementation>
   <Implementation_path>
      C:\Dependency\xmlMetadata\xmlMetadata1.cpp
   </Implementation_path>
</Dependency>

</Dependency_Details>
</fileStructure>

代码的基本概念是 while > line ，请剥掉开头的空格，并将 new-stripped-string 存入 tmp ，然后尝试匹配到您要查找的标签之一。找到 begin-tag 后，请继续打印以下行，直到找到关闭标签。

The basic idea of the code is while you are reading each line of the file, strip the white spaces that are in the beginning and store the new-stripped-string into tmp, and then try to match it to one of the tags you are looking for. Once you find the begin-tag, keep printing the following lines until the close-tag is found.

文件： parse.cpp

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

using namespace std;

int main()
{
    string line;
    ifstream in("demo.xml");

    bool begin_tag = false;
    while (getline(in,line))
    {
        std::string tmp; // strip whitespaces from the beginning
        for (int i = 0; i < line.length(); i++)
        {
            if (line[i] == ' ' && tmp.size() == 0)
            {
            }
            else
            {
                tmp += line[i];
            }
        }

        //cout << "-->" << tmp << "<--" << endl;

        if (tmp == "<Package>")
        {
            //cout << "Found <Package>" << endl;
            begin_tag = true;
            continue;
        }
        else if (tmp == "</Package>")
        {
            begin_tag = false;
            //cout << "Found </Package>" << endl;
        }

        if (begin_tag)
        {
            cout << tmp << endl;
        }
    }
}

/ strong>

Outputs:

xmlMetadata
xmlMetadata1

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