c++ - libxml2 获取验证错误

Question

我正在使用 libxml2 根据 xsd 模式验证 xml 文件。使用 xmlSchemaSetParserErrors 函数，将错误输出到 stderr。我需要获取这些验证错误，将它们存储在内存中并显示给用户。如何重定向这些错误？你能给我一些例子吗？谢谢，安德里亚

Answer 1

这个例子使用了解析器模块的验证回调机制。 xmlSchemaSetParserErrors 预期的回调签名似乎是相同的。

#include <iostream>
#include <cstdarg>
#include <cstdio>
#include <vector>
#include <string>
#include <iterator>
#include <libxml/parser.h>
#include <libxml/tree.h>

struct ParserContext
{
    ParserContext() : context(xmlNewParserCtxt()) {}
    ~ParserContext() { xmlFreeParserCtxt(context); }
    xmlParserCtxtPtr context;
private:
    ParserContext(ParserContext&);
    void operator=(ParserContext&);
};



struct ErrorHandler
{
    std::vector<std::string> errors;

    void RegisterErrorHandling(xmlValidCtxt& validationContext)
    {
        // Change this to register for schema errors...
        validationContext.userData = this;
        validationContext.error = &ErrorHandler::Handle;
    }

private:
    static void Handle(void *handler, const char *format, ...)
    {
        va_list arguments;
        va_start(arguments, format);
        std::string message = MakeMessage(format, arguments);
        va_end(arguments);

        ErrorHandler* errorHandler = static_cast<ErrorHandler*>(handler);
        errorHandler->errors.push_back(message);
    }

    static std::string MakeMessage(const char* format, va_list arguments)
    {
        const size_t bufferSize = 200;
        std::vector<char> buffer(bufferSize, 0);

        size_t charactersWritten = 
            vsnprintf(&buffer.front(), bufferSize, format, arguments);
        if (charactersWritten == -1)
            buffer.back() = 0;  // Message truncated!
        return std::string(&buffer.front());
    }
};


struct XmlDocument
{
    static XmlDocument FromFile(const char* fileName)
    {
        ParserContext parser;
        ErrorHandler errorHandler;
        errorHandler.RegisterErrorHandling(parser.context->vctxt);
        XmlDocument document(xmlCtxtReadFile(
            parser.context, fileName, NULL, XML_PARSE_DTDVALID));
        document.errors = move(errorHandler.errors);
        return document;
    }

    XmlDocument(XmlDocument&& other) : 
        xmlPointer(other.xmlPointer),
        errors(move(other.errors))
    {
        other.xmlPointer = nullptr;
    }

    ~XmlDocument() 
    { 
        xmlFreeDoc(xmlPointer); 
    }

    xmlDocPtr xmlPointer;
    std::vector<std::string> errors;

private:
    XmlDocument(xmlDocPtr pointer) : xmlPointer(pointer) {}
    XmlDocument(XmlDocument&);
    void operator=(XmlDocument&);
};


void DisplayErrorsToUser(
    const XmlDocument& document, 
    std::ostream& displayStream = std::cout)
{
    using namespace std;
    copy(begin(document.errors), end(document.errors),
        ostream_iterator<string>(displayStream, "\n"));
}

int main()
{
    auto xml = XmlDocument::FromFile("test.xml");
    DisplayErrorsToUser(xml);
}