Question

我正在使用boost :: property_tree在我的应用程序中读写XML配置文件。但是当我写文件时，输出看起来很丑陋，文件中有很多空行。问题是它应该由人类编辑，所以我想获得更好的输出。

作为一个例子，我写了一个小测试程序：

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>

int main( void )
{
    using boost::property_tree::ptree;
    ptree pt;

    // reading file.xml
    read_xml("file.xml", pt);

    // writing the unchanged ptree in file2.xml
    boost::property_tree::xml_writer_settings<char> settings('\t', 1);
    write_xml("file2.xml", pt, std::locale(), settings);

    return 0;
}

file.xml包含：

<?xml version="1.0" ?>
<config>
    <net>
        <listenPort>10420</listenPort>
    </net>
</config>

运行程序后，file2.xml包含：

<?xml version="1.0" encoding="utf-8"?>
<config>



    <net>



        <listenPort>10420</listenPort>
    </net>
</config>

有没有办法获得更好的输出，除了手动通过输出并删除空行？

Answer 1

解决方案是将trim_whitespace标记添加到read_xml的调用中：

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>

int main( void )
{
    // Create an empty property tree object
    using boost::property_tree::ptree;
    ptree pt;

    // reading file.xml
    read_xml("file.xml", pt, boost::property_tree::xml_parser::trim_whitespace );

    // writing the unchanged ptree in file2.xml
    boost::property_tree::xml_writer_settings<char> settings('\t', 1);
    write_xml("file2.xml", pt, std::locale(), settings);

    return 0;
}

该标志记录在here但是图书馆的当前维护者（Sebastien Redl）非常友好地回答并指出了它。

Answer 2

这个问题很老了，但我最近再次调查了你的问题，因为现在property_tree将换行符转换为

后情况变得更糟

&#10;

在我看来，这是一个错误，因为只包含空格的元素 - 换行符，空格和制表符，被视为文本元素。 trim_whitespace只是一个bandaid并规范化property_tree中的所有空格。

我在这里报告了这个错误并附加了一个.diff来修复Boost 1.59中的这种行为，以防不使用trim_whitespace： https://svn.boost.org/trac/boost/ticket/11600

Answer 3

对于那些尝试：

boost::property_tree::xml_writer_settings<char> settings('\t', 1);

使用VisualStudio 2013中的boost-1.60.0进行编译，您可能会得到：

vmtknetworktest.cpp(259) : see reference to class template instantiation 'boost::property_tree::xml_parser::xml_writer_settings<char>' being compiled
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(38): error C2039: 'value_type' : is not a member of '`global namespace''
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(38): error C2146: syntax error : missing ';' before identifier 'Ch'
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(38): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(40): error C2061: syntax error : identifier 'Ch'
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(49): error C2146: syntax error : missing ';' before identifier 'indent_char'
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(49): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(50): error C2825: 'Str': must be a class or namespace when followed by '::'
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(50): error C2039: 'size_type' : is not a member of '`global namespace''
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(50): error C2146: syntax error : missing ';' before identifier 'indent_count'
install\include\boost-1_60\boost/property_tree/detail/xml_parser_writer_settings.hpp(50): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
vmtknetworktest.cpp(259): error C2661: 'boost::property_tree::xml_parser::xml_writer_settings<char>::xml_writer_settings' : no overloaded function takes 3 arguments

然后结束：

https://svn.boost.org/trac/boost/ticket/10272

找到工作的解决方案是在模板中使用std :: string。

pt::write_xml(file_name, params, std::locale(), pt::xml_writer_make_settings< std::string >(' ', 4));

如下所述：

https://stackoverflow.com/a/35043551/7170333

boost :: property_tree XML漂亮打印

3 个答案: