RapidXML throwing a parse_error exception

Question

When I try to parse a simple .xml file using the RapidXML framework, it throws a parse_error with this cause: "expected <". Now this is practically my first time writing XML code, so it might be a silly syntax error, in that case, bear with me :) This is my xmlParser.h:

#ifndef __XML_PARSER_H__
#define __XML_PARSER_H__

#include "rapidxml.hpp"
#include "windowUtil.h"

class XmlParser
{
public:
    bool parse(char *xml)
    {
        try
        {
            doc.parse<0>(xml);
        }
        catch(rapidxml::parse_error &e)
        {
            msg_box(NULL, e.what(), "RapidXML exception!", MB_OK | MB_ICONERROR | MB_TASKMODAL);

            return false;
        }

        return true;
    }

    char* get_first_node_name()
    {
        return doc.first_node()->name();
    }
private:
    rapidxml::xml_document<> doc;
};

#endif

And this is how it is called and used:

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance, LPSTR lpcmdline, int ncmdshow)
{
    XmlParser xmlParser;
    WindowFramework *window = create_window(&framework, NULL, NULL, "GAME");

    if(!init_window(window, true, true))
        return kill(1);
    if(!xmlParser.parse("./layouts/login_gui.xml"))
        return kill(1);

    framework.main_loop();

    return kill(0);
}

login_gui.xml:

<?xml version="1.0"?>
<button>
    <text>EXIT</text>
    <buttonready>button.png</buttonready>
    <buttonrollover>button_active.png</buttonrollover>
    <buttonpressed>button_pressed.png</buttonpressed>
    <buttoninactive>button_inactive.png</buttoninactive>
</button>

Steve Townsend · Accepted Answer · 2011-06-13T17:50:34.770

3

The parse method takes a string containing XML, you are passing it a filename. Your filename is being treated as the XML data and obviously that's not right. You must read in the file first, and then call parse with the resulting string.

From the RapidXML docs:

function xml_document::parse

Synopsis

void parse(Ch *text);

Description

Parses zero-terminated XML string according to given flags.

Your revised structure could be something like

bool parse(char *xmlFile)        
{            
     try            
     {  
        std::string xml(getXmlDataFromFile(xmlFile));
        doc.parse<0>(xml.c_str());            
     }

edited Jun 13 '11 at 17:50

answered Jun 13 '11 at 16:45

Steve Townsend

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Guess I should have learned how to crawl before I started walking.. :) – Benjamin Jun 13 '11 at 16:47
2

Don't sweat it, these C++ XML APIs are rarely intuitive. Best of luck. – Steve Townsend Jun 13 '11 at 16:56

score 3 · Answer 2 · edited May 23 '17 at 10:00

There's a fine document on using RapidXML that I always refer to. It's a must read!

Here is my attempt to read the first nodes of your document (demo.xml).

string input_xml;
string line;
ifstream in("demo.xml");

// read file into input_xml
while(getline(in,line))
    input_xml += line;

// make a safe-to-modify copy of input_xml
// (you should never modify the contents of an std::string directly)
vector<char> xml_copy(input_xml.begin(), input_xml.end());
xml_copy.push_back('\0');

// only use xml_copy from here on!
xml_document<> doc;
// we are choosing to parse the XML declaration
// parse_no_data_nodes prevents RapidXML from using the somewhat surprising
// behavior of having both values and data nodes, and having data nodes take
// precedence over values when printing
// >>> note that this will skip parsing of CDATA nodes <<<
doc.parse<parse_declaration_node | parse_no_data_nodes>(&xml_copy[0]);

// we didn't keep track of our previous traversal, so let's start again
// we can match nodes by name, skipping the xml declaration entirely
xml_node<>* cur_node = doc.first_node("button");

// go straight to the first text node
cur_node = cur_node->first_node("text");
string text = cur_node->value(); // if the node doesn't exist, this line will crash
cout << text << endl;

// and then to the next node
cur_node = cur_node->next_sibling("buttonready");
string b_ready = cur_node->value();
cout << b_ready << endl;

// and then to the next node
// ...

Outputs:

EXIT
button.png

If in the future your XML gets more complex, you could take a look at this answer:

Read a line from xml file using C++

which shows a source code that also read properties from nodes.

RapidXML throwing a parse_error exception

2 Answers2