boost read_xml from stringstream does not read xml format

Question

I want to fill a boost::property_tree::ptree with the data from a xml, the xml format is in a string which I passed to stringstream and then I try to read it with read_xml, but the ptree data is null or empty when I look at the object while debugging, my code:

std::stringstream ss;
ss << "<?xml ?><root><test /></root>";
boost::property_tree::ptree pt;
boost::property_tree::xml_parser::read_xml( ss, pt);

result:

pt {m_data="" m_children=0x001dd3b0 }

before I had a string with this xml code:

<?xml version="1.0"?><Response Location="910" RequesterId="12" SequenceNumber="0">
<Id>1</Id>
<Type>P</Type>
<StatusMessage></StatusMessage>
<Message>Error</Message>
</Response>

But nothing works using visual studio with c++.

Answer 1

There is no data associated with root node so m_data is empty but there is a child node (test) and m_children != nullptr.

Please consider this example:

#include <sstream>
#include <string>
#include <boost/property_tree/xml_parser.hpp>

int main()
{
  std::stringstream ss;
  ss << "<?xml ?><root><test /></root>";
  boost::property_tree::ptree pt;
  boost::property_tree::xml_parser::read_xml(ss, pt);

  // There is no data associated with root node...
  std::string s(pt.get<std::string>("root"));
  std::cout << "EXAMPLE1" << std::endl << "Data associated with root node: " << s << std::endl;

  // ...but there is a child node.
  std::cout << "Children of root node: ";
  for (auto r : pt.get_child("root"))
    std::cout << r.first << std::endl;

  std::cout << std::endl << std::endl;

  std::stringstream ss2;
  ss2 << "<?xml ?><root>dummy</root>";
  boost::property_tree::xml_parser::read_xml(ss2, pt);

  // This time we have a string associated with root node
  std::string s2(pt.get<std::string>("root"));
  std::cout << "EXAMPLE2" << std::endl << "Data associated with root node: " << s2 << std::endl;

  return 0;
}

It'll print:

EXAMPLE1
Data associated with root node: 
Children of root node: test

EXAMPLE2
Data associated with root node: dummy

(http://coliru.stacked-crooked.com/a/34a99abb0aca78f2).

The Boost propertytree library doesn’t fully document its capabilities, but a good guide for parsing XML with Boost is http://akrzemi1.wordpress.com/2011/07/13/parsing-xml-with-boost/