Debutant Libxml2 et C recherche de données dans XML

**Mika2008** · 17/02/2011, 21h14

Bonjour,

voila j’aimerais rechercher des données dans un fichier XML, Pour n'en garder que certain.

j'ai regarder des codes d'emple de libxml2, mais ils ne sont pas trés clair.

et je n'est rien trouvé sur comment rechercher une information d'une balise dans un xml.
quelqu'un peut m'aiguiller svp ?

merci @ vous.

**Mika2008** · 17/02/2011, 21h50

Par exemple ce code :

Code :

Sélectionner tout - Visualiser dans une fenêtre à part

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#include <libxml/parser.h>
#include <libxml/xpath.h>
 
xmlDocPtr
getdoc (char *docname) {
	xmlDocPtr doc;
	doc = xmlParseFile(docname);
 
	if (doc == NULL ) {
		fprintf(stderr,"Document not parsed successfully. \n");
		return NULL;
	}
 
	return doc;
}
 
xmlXPathObjectPtr
getnodeset (xmlDocPtr doc, xmlChar *xpath){
 
	xmlXPathContextPtr context;
	xmlXPathObjectPtr result;
 
	context = xmlXPathNewContext(doc);
	if (context == NULL) {
		printf("Error in xmlXPathNewContext\n");
		return NULL;
	}
	result = xmlXPathEvalExpression(xpath, context);
	xmlXPathFreeContext(context);
	if (result == NULL) {
		printf("Error in xmlXPathEvalExpression\n");
		return NULL;
	}
	if(xmlXPathNodeSetIsEmpty(result->nodesetval)){
		xmlXPathFreeObject(result);
                printf("No result\n");
		return NULL;
	}
	return result;
}
int
main(int argc, char **argv) {
 
	char *docname;
	xmlDocPtr doc;
xmlChar *xpath = (xmlChar*) "//feed//entry//id";
	xmlNodeSetPtr nodeset;
	xmlXPathObjectPtr result;
	int i;
	xmlChar *keyword;
 
	if (argc <= 1) {
		printf("Usage: %s docname\n", argv[0]);
		return(0);
	}
 
	docname = argv[1];
	doc = getdoc(docname);
	result = getnodeset (doc, xpath);
	if (result) {
		nodeset = result->nodesetval;
		for (i=0; i < nodeset->nodeNr; i++) {
			keyword = xmlNodeListGetString(doc, nodeset->nodeTab[i]->xmlChildrenNode, 1);
		printf("keyword: %s\n", keyword);
		xmlFree(keyword);
		}
		xmlXPathFreeObject (result);
	}
	xmlFreeDoc(doc);
	xmlCleanupParser();
	return (1);
}

je travaille sur ce fichier XML :

Code :

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<?xml version='1.0' encoding='UTF-8'?>
<feed xmlns='http://www.w3.org/2005/Atom' xmlns:media='http://search.yahoo.com/mrss/' xmlns:openSearch='http://a9.com/-/spec/opensearch/1.1/' xmlns:gd='http://schemas.google.com/g/2005' xmlns:yt='http://gdata.youtube.com/schemas/2007' gd:etag='W/&quot;DEYEQX87fyp7ImA9Wx9UF00.&quot;'>
	<id>tag:youtube.com,2008:videos</id>
	<updated>2011-02-14T17:55:00.107Z</updated>
	<category scheme='http://schemas.google.com/g/2005#kind' term='http://gdata.youtube.com/schemas/2007#video'/>
	<title>YouTube Videos matching query: Ronald Jenkees</title>
	<logo>http://www.youtube.com/img/pic_youtubelogo_123x63.gif</logo>
	<link rel='alternate' type='text/html' href='http://www.youtube.com'/>
	<link rel='http://schemas.google.com/g/2005#feed' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos?v=2'/>
	<link rel='http://schemas.google.com/g/2005#batch' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/batch?v=2'/>
	<link rel='self' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos?q=Ronald+Jenkees&amp;start-index=1&amp;max-results=2&amp;v=2'/>
	<link rel='service' type='application/atomsvc+xml' href='http://gdata.youtube.com/feeds/api/videos?alt=atom-service&amp;v=2'/>
	<link rel='next' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos?q=Ronald+Jenkees&amp;start-index=3&amp;max-results=2&amp;v=2'/>
	<author>
		<name>YouTube</name>
		<uri>http://www.youtube.com/</uri>
	</author>
	<generator version='2.0' uri='http://gdata.youtube.com/'>YouTube data API</generator>
	<openSearch:totalResults>2715</openSearch:totalResults>
	<openSearch:startIndex>1</openSearch:startIndex>
	<openSearch:itemsPerPage>2</openSearch:itemsPerPage>
	<entry gd:etag='W/&quot;D0ANQX47eCp7ImA9Wx9UFkQ.&quot;'>
		<id>tag:youtube.com,2008:video:smE-uIljiGo</id>
		<published>2008-03-06T18:36:43.000Z</published>
		<updated>2011-02-14T15:03:10.000Z</updated>
		<category scheme='http://schemas.google.com/g/2005#kind' term='http://gdata.youtube.com/schemas/2007#video'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/categories.cat' term='Music' label='Music'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='ronald'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='jenkees'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='unsigned'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='motif'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='XS'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='XS8'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='keyboard'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='guitar'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='jam'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='beat'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='fl'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='studio'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='fruityloops'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='hip-hop'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='solo'/>
		<category scheme='http://gdata.youtube.com/schemas/2007/keywords.cat' term='instrumental'/>
		<title>Ronald Jenkees - Guitar Sound</title>
		<content type='application/x-shockwave-flash' src='http://www.youtube.com/v/smE-uIljiGo?f=videos&amp;app=youtube_gdata'/>
		<link rel='alternate' type='text/html' href='http://www.youtube.com/watch?v=smE-uIljiGo&amp;feature=youtube_gdata'/>
		<link rel='http://gdata.youtube.com/schemas/2007#video.responses' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/smE-uIljiGo/responses?v=2'/>
		<link rel='http://gdata.youtube.com/schemas/2007#video.related' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/smE-uIljiGo/related?v=2'/>
		<link rel='http://gdata.youtube.com/schemas/2007#mobile' type='text/html' href='http://m.youtube.com/details?v=smE-uIljiGo'/>
		<link rel='self' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/smE-uIljiGo?v=2'/>
		<author>
			<name>ronaldjenkees</name>
			<uri>http://gdata.youtube.com/feeds/api/users/ronaldjenkees</uri>
			</author>
			<yt:accessControl action='comment' permission='allowed'/>
			<yt:accessControl action='commentVote' permission='allowed'/>
			<yt:accessControl action='videoRespond' permission='moderated'/>
			<yt:accessControl action='rate' permission='allowed'/>
			<yt:accessControl action='embed' permission='allowed'/>
			<yt:accessControl action='list' permission='allowed'/>
			<yt:accessControl action='syndicate' permission='allowed'/>
			<gd:comments>
				<gd:feedLink href='http://gdata.youtube.com/feeds/api/videos/smE-uIljiGo/comments?v=2' countHint='28562'/>
				</gd:comments>
				<media:group>
					<media:category label='Music' scheme='http://gdata.youtube.com/schemas/2007/categories.cat'>Music</media:category>
					<media:content url='http://www.youtube.com/v/smE-uIljiGo?f=videos&amp;app=youtube_gdata' type='application/x-shockwave-flash' medium='video' isDefault='true' expression='full' duration='255' yt:format='5'/>
					<media:content url='rtsp://v2.cache1.c.youtube.com/CiILENy73wIaGQlqiGOJuD5hshMYDSANFEgGUgZ2aWRlb3MM/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='255' yt:format='1'/>
					<media:content url='rtsp://v1.cache5.c.youtube.com/CiILENy73wIaGQlqiGOJuD5hshMYESARFEgGUgZ2aWRlb3MM/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='255' yt:format='6'/>
					<media:credit role='uploader' scheme='urn:youtube' yt:type='partner'>ronaldjenkees</media:credit>
					<media:description type='plain'>download the MP3: www.ronaldjenkees.com **this tune is on my new CD, Disorganized Fun. I named it Guitar Sound. just havin some fun with a guitar sound (Hard Ramp AS1&amp;2) on the Motif XS8. Some have asked about the "low notes" that come out when I hit those two keys up top - those are guitar effects built in the patch and for whatever reason, Yamaha put those effects on the high keys. I made the background beat using FL Studio. I start the beat by hitting the space-bar on my computer keyboard before I play on the synth. PS. I've read some reviews of this vid as if I'm trying to be a "keytar" player (apparently not a desirable thing, but how can you not like Edgar Winter's "Frankenstein") and that I should just play a real guitar. LOL @ some of those same people who probably play guitar hero (nothing against it but hopefully you see my point)! The irony! The point is, folks, if you find a fun/inspiring sound to jam with, by all means, you should JAM WITH IT! I don't care if you find a $3.00 plastic trumpet. Don't worry about the technicalities and what people say. In the long run it's about the fun that YOU have making music. Thanks for watching!!!</media:description>
					<media:keywords>ronald, jenkees, unsigned, motif, XS, XS8, keyboard, guitar, jam, beat, fl, studio, fruityloops, hip-hop, solo, instrumental</media:keywords>
					<media:player url='http://www.youtube.com/watch?v=smE-uIljiGo&amp;feature=youtube_gdata_player'/>
					<media:thumbnail url='http://i.ytimg.com/vi/smE-uIljiGo/default.jpg' height='90' width='120' time='00:02:07.500' yt:name='default'/>
					<media:thumbnail url='http://i.ytimg.com/vi/smE-uIljiGo/hqdefault.jpg' height='360' width='480' yt:name='hqdefault'/>
					<media:thumbnail url='http://i.ytimg.com/vi/smE-uIljiGo/1.jpg' height='90' width='120' time='00:01:03.750' yt:name='start'/>
					<media:thumbnail url='http://i.ytimg.com/vi/smE-uIljiGo/2.jpg' height='90' width='120' time='00:02:07.500' yt:name='middle'/>
					<media:thumbnail url='http://i.ytimg.com/vi/smE-uIljiGo/3.jpg' height='90' width='120' time='00:03:11.250' yt:name='end'/>
					<media:title type='plain'>Ronald Jenkees - Guitar Sound</media:title>
					<yt:duration seconds='255'/>
					<yt:uploaded>2008-03-06T18:36:43.000Z</yt:uploaded>
					<yt:videoid>smE-uIljiGo</yt:videoid>
					</media:group>
	<yt:statistics favoriteCount='52741' viewCount='7247365'/>
	</entry>
	<entry gd:etag='W/&quot;DkMBRn47eCp7ImA9Wx9UFkQ.&quot;'>
						<id>tag:youtube.com,2008:video:0O2aH4XLbto</id>
						<published>2008-08-05T21:56:54.000Z</published>
						<updated>2011-02-14T14:40:57.000Z</updated>
						<category scheme='http://schemas.google.com/g/2005#kind' term='http://gdata.youtube.com/schemas/2007#video'/>
						<category scheme='http://gdata.youtube.com/schemas/2007/categories.cat' term='Music' label='Music'/>
						<title>Ronald Jenkees - Throwing Fire</title>
						<content type='application/x-shockwave-flash' src='http://www.youtube.com/v/0O2aH4XLbto?f=videos&amp;app=youtube_gdata'/>
						<link rel='alternate' type='text/html' href='http://www.youtube.com/watch?v=0O2aH4XLbto&amp;feature=youtube_gdata'/>
						<link rel='http://gdata.youtube.com/schemas/2007#video.responses' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/0O2aH4XLbto/responses?v=2'/>
						<link rel='http://gdata.youtube.com/schemas/2007#video.related' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/0O2aH4XLbto/related?v=2'/>
						<link rel='http://gdata.youtube.com/schemas/2007#mobile' type='text/html' href='http://m.youtube.com/details?v=0O2aH4XLbto'/>
						<link rel='self' type='application/atom+xml' href='http://gdata.youtube.com/feeds/api/videos/0O2aH4XLbto?v=2'/>
						<author>
							<name>ronaldjenkees</name>
							<uri>http://gdata.youtube.com/feeds/api/users/ronaldjenkees</uri>
							</author>
							<yt:accessControl action='comment' permission='allowed'/>
							<yt:accessControl action='commentVote' permission='allowed'/>
							<yt:accessControl action='videoRespond' permission='moderated'/>
							<yt:accessControl action='rate' permission='allowed'/>
							<yt:accessControl action='embed' permission='allowed'/>
							<yt:accessControl action='list' permission='allowed'/>
							<yt:accessControl action='syndicate' permission='allowed'/>
							<gd:comments>
								<gd:feedLink href='http://gdata.youtube.com/feeds/api/videos/0O2aH4XLbto/comments?v=2' countHint='28675'/>
								</gd:comments>
								<media:group>
									<media:category label='Music' scheme='http://gdata.youtube.com/schemas/2007/categories.cat'>Music</media:category>
									<media:content url='http://www.youtube.com/v/0O2aH4XLbto?f=videos&amp;app=youtube_gdata' type='application/x-shockwave-flash' medium='video' isDefault='true' expression='full' duration='190' yt:format='5'/>
									<media:content url='rtsp://v4.cache2.c.youtube.com/CiILENy73wIaGQnabsuFH5rt0BMYDSANFEgGUgZ2aWRlb3MM/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='190' yt:format='1'/>
									<media:content url='rtsp://v2.cache1.c.youtube.com/CiILENy73wIaGQnabsuFH5rt0BMYESARFEgGUgZ2aWRlb3MM/0/0/0/video.3gp' type='video/3gpp' medium='video' expression='full' duration='190' yt:format='6'/>
									<media:credit role='uploader' scheme='urn:youtube' yt:type='partner'>ronaldjenkees</media:credit>
									<media:description type='plain'>Throwing Fire is on my 2nd CD, Disorganized Fun: www.ronaldjenkees.com SUPER FUN TIME WITH THIS JAM!!!! Thanks a lot for watching! Hope you liked it. Kindof a rough cut, but it's always fun. This video is dedicated to the band Papa Roach for letting me check out their studio and giving me a place to stay in LA. Those are some hard-working rockers and good guys. I got cold chills listening to the songs they're working on for their new album. I think it's coming out really soon. My friend Sam gave me the hat I'm wearing in this vid. It's made of 100% recycled material. Can't beat that. Here's their site: www.livity.org I'm using FL Studio software to make the beat in the background and a Korg Triton Le keyboard on top, Motif XS8 on bottom.</media:description>
									<media:keywords/>
									<media:player url='http://www.youtube.com/watch?v=0O2aH4XLbto&amp;feature=youtube_gdata_player'/>
									<media:thumbnail url='http://i.ytimg.com/vi/0O2aH4XLbto/default.jpg' height='90' width='120' time='00:01:35' yt:name='default'/>
									<media:thumbnail url='http://i.ytimg.com/vi/0O2aH4XLbto/hqdefault.jpg' height='360' width='480' yt:name='hqdefault'/>
									<media:thumbnail url='http://i.ytimg.com/vi/0O2aH4XLbto/1.jpg' height='90' width='120' time='00:00:47.500' yt:name='start'/>
									<media:thumbnail url='http://i.ytimg.com/vi/0O2aH4XLbto/2.jpg' height='90' width='120' time='00:01:35' yt:name='middle'/>
									<media:thumbnail url='http://i.ytimg.com/vi/0O2aH4XLbto/3.jpg' height='90' width='120' time='00:02:22.500' yt:name='end'/>
									<media:title type='plain'>Ronald Jenkees - Throwing Fire</media:title>
									<yt:duration seconds='190'/>
									<yt:uploaded>2008-08-05T21:56:54.000Z</yt:uploaded>
									<yt:videoid>0O2aH4XLbto</yt:videoid>
									</media:group>
									<yt:statistics favoriteCount='52285' viewCount='6488178'/>
</entry>
</feed>

en théorie dans le code C je lui demande de m'afficher le contenue de la balise //feed//entry//id
xmlChar *xpath = (xmlChar*) "//feed//entry//id";

quand ke lance le programme il met me no result ?
alors qu'il aurait du m'afficher :
tag:youtube.com,2008:video:smE-uIljiGo
ce que contient la balise //feed/entry/if

qu'en pensez vous svp ?

**Erwy** · 18/02/2011, 06h20

je ne connais pas bien cette bibliotheque mais, le problème vient sans doute que tu utilises un namespace (non préfixé pour tout arrangé).

xmlns='http://www.w3.org/2005/Atom'
Et il faudrait le passer en paramètre à ta fonction

Pour ce que j'ai trouvé sur le web essaye quelque chose comme

Code :

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 getnodeset (doc, xpath,'http://www.w3.org/2005/Atom')

**Mika2008** · 18/02/2011, 15h35

merci de ta réponse, mais ce le ne fonctionne pas :

dans mon code je met ceci :

Code :

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xmlChar *xpath = (xmlChar*) "http://www.w3.org/2005/Atom";

ce qui me donne comme résultat :

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XPath error : Invalid expression
http://www.w3.org/2005/Atom
     ^
XPath error : Invalid expression
http://www.w3.org/2005/Atom
     ^
Error in xmlXPathEvalExpression

**Mika2008** · 18/02/2011, 18h38

j'ai trouvé ce petit article :

http://xmlsoft.org/namespaces.html

mais c'est pas trés claire?

**Mika2008** · 18/02/2011, 23h30

j'ai trouvé un début de réponse ici :

urns out, as I found out from here, it is not really a failure of libXml, it's a problem because libXml correctly follows the XML/XPATH specifications.

The solutions proposed by R Bourdeau are correct, however, if you have control of the xml document you are parsing.

The context for the XPATH query is independent of the namespace qualifiers in the xml document. The default namespace forces all child tags into a namespace; they don't require qualification in the document but must be qualified in the xpath query. Fortunately, you registered the namespace as new with libXml, so cateof's solution should work.

xmlXPathRegisterNs(context, BAD_CAST "new", BAD_CAST "http://www.example.com/new"

xmlChar *xpath = (xmlChar*) "/new:book/new:section1";
I'm inlining the xml here for visibility:

<?xml version="1.0" encoding="UTF-8"?>
<book xmlns="http://www.example.com/new">
<section1>Sec_1</section1>
<section2>Sec_2</section2>
</book>

par contre les balises comme ceci je n'arrive pas à extraire la donnée, le programme ne trouve pas cette balise :

Code :

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<yt:videoid>

par exemple si je tape cette recherche :

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xmlChar *xpath_id_video= (xmlChar*) "/feed:feed/feed:entry/feed:media/feed:group/feed:yt/feed:videoid";

je continue à chercher

Debutant Libxml2 et C recherche de données dans XML

XSL/XSLT/XPATH XML

Vue hybride

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