Re: What is a pre-compiled XPath expression and does Xerces support it???

[Ben Griffin]

I'm not sure if you are using DOM - but if you are, I recently wrote a small 
example/test that includes pre-compile XPaths.
This depends heavily on XQilla - which I am sure most XercesC developers/users 
recommend if you are planning on using XPaths.
I am using the XQilla "SimpleAPI" - which allows for more optimal approaches to 
applications that heavily depend upon XPaths.

Anyway, I include the code - hoping it may help you with this sort of stuff.

#include <iostream>
#include <fstream>
#include <xqilla/xqilla-dom3.hpp>
#include <xqilla/xqilla-simple.hpp>
#include <xercesc/util/PlatformUtils.hpp>
#include <xercesc/util/XercesDefs.hpp>
#include <xercesc/dom/DOM.hpp>

/*
 File foo.xml is as follows.
 <?xml version="1.0" encoding="UTF-8" standalone="no" ?>
 <!DOCTYPE div><div xmlns="http://www.w3.org/1999/xhtml";>
 <h5>Foo</h5><div><span class="phoo">wibble</span></div>
 </div>
 
 File bar.xml is as follows.
 <?xml version="1.0" encoding="utf-8"?>
 <!DOCTYPE div><div xmlns="http://www.w3.org/1999/xhtml";>
 <h5>Bar</h5><div><span class="bah">wobble</span></div>
 </div>
 */

using namespace xercesc;
using namespace std;

class errhandler : public DOMErrorHandler {
public:
        bool handleError(const DOMError& domError) {
                cout << UTF8(domError.getMessage()); return true;
        }
};

errhandler*                             err     = NULL;

//dom
DOMImplementation*              impl    = NULL;
DOMLSParser*                    parser  = NULL;
DOMDocument*                    d1              = NULL;
DOMDocument*                    d2              = NULL;

//xqilla
DynamicContext*                 central = NULL;
XQilla*                                 xqilla  = NULL;
XercesConfiguration*    xc              = NULL;
XQQuery*                                q1              = NULL;
XQQuery*                                q2              = NULL;

DOMDocument* DOMDocFromFile(const XMLCh* const uri) {
        DOMDocument* rslt = NULL;
        try {
                rslt = parser->parseURI(uri);
        } catch (...) {
                std::cout << "DOM Parse error" << std::endl;
        }
        return rslt;
}

void doDocQuery(DOMDocument* d,XQQuery* q) {
        DOMElement* el = d->getDocumentElement();
        if (el != NULL) {
                AutoDelete<DynamicContext> c(q->createDynamicContext());
                
c->setContextItem(((XercesConfiguration*)c->getConfiguration())->createNode(el,c));
                Result result = q->execute(c);
                Item::Ptr item;
                while((item = result->next(c))) {
                        std::cout << UTF8(item->asString(c)) << ";";
                }
        }
}

int main(int argc, char *argv[]) {
        err = new errhandler();
        XQillaPlatformUtils::initialize();
        xqilla = new XQilla();
        xc = new XercesConfiguration();
        impl = DOMImplementationRegistry::getDOMImplementation(X("XPath2 3.0"));
        parser = 
((DOMImplementationLS*)impl)->createLSParser(DOMImplementationLS::MODE_SYNCHRONOUS,NULL);
        DOMConfiguration* dc = parser->getDomConfig();
        dc->setParameter(XMLUni::fgDOMErrorHandler,err);
        dc->setParameter(XMLUni::fgXercesUserAdoptsDOMDocument,true);
        central = xqilla->createContext(XQilla::XPATH3,xc);
        central->setNamespaceBinding(X("h"),X("http://www.w3.org/1999/xhtml";));
        q1 = xqilla->parse(X("//h:span[@class]/@class"),central,NULL,0x12);
        q2 = xqilla->parse(X("//h:h5/text()"),central,NULL,0x12);
    //initialise process is done
        for (int i = 1; i <= 100; i++) {
                cout << "iteration " << i << ":";
                d1 = DOMDocFromFile(X("foo.xml"));
                d2 = DOMDocFromFile(X("bar.xml"));
                doDocQuery(d1,q1);
                doDocQuery(d1,q2);
                doDocQuery(d2,q1);
                doDocQuery(d2,q2);
                d1->release();
                d2->release();
                cout << endl;
        }
    //now teardown variables
        delete q1;
        delete q2;
        delete central;
        parser->release();
        delete xc;
        delete xqilla;
        delete err;
        return 0;
}

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