c语言libxml2使用xpath解析示例

1.xml文件样本xpathtest.xml

<?xml version="1.0" encoding="UTF-8"?> 
<radios> 
    <radio> 
        <name>Bayern</name> 
        <url>http://mp3.webradio.antenne.de:80</url> 
        <classification> 
            <area>usa</area> 
            <style>music</style> 
        </classification> 
    </radio> 
    <radio> 
        <name>DEU-Antenne Bayern</name> 
        <url>http://mp3.webradio.antenne.de:80</url> 
    </radio> 
    <radio> 
        <name>DEU-Antenne Bayern</name> 
        <url>http://test</url> 
    </radio> 
</radios> 

2.源码实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libxml/parser.h>
#include <libxml/xpath.h>

xmlXPathObjectPtr getNodeSet(xmlDocPtr doc, const xmlChar *xpath)
{
    xmlXPathContextPtr context;
    xmlXPathObjectPtr result;

    context = xmlXPathNewContext(doc);

    if(context == NULL)
    {
        printf("context is NULL\n");
        return NULL;
    }

    result = xmlXPathEvalExpression(xpath, context);

    xmlXPathFreeContext(context);

    if(result == NULL)
    {
        printf("xmlXPathEvalExpression return NULL\n");
        return NULL;
    }

    if(xmlXPathNodeSetIsEmpty(result->nodesetval))
    {
        xmlXPathFreeObject(result);
        printf("nodeset is empty\n");
        return NULL;
    }

    return result;
}

int main(int argc, char **argv)
{
    xmlDocPtr doc;
    xmlChar *xpath = BAD_CAST("/radios/radio[name='DEU-Antenne Bayern']");
    xmlChar *value = NULL;
    xmlXPathObjectPtr appResult = NULL;
    xmlNodeSetPtr nodeset = NULL;
    xmlNodePtr cur = NULL;
    char *szDocName;
    int i;

    if(argc <= 1)
    {
        printf("Usage: %s docname\n", argv[0]);
        return 0;
    }

    szDocName = argv[1];

    /*解析文件*/
    doc = xmlReadFile(szDocName, "UTF-8", XML_PARSE_RECOVER);

    if(doc == NULL)
    {
        fprintf(stderr, "Document not parsed successful.\n");
        return -1;
    }

    appResult = getNodeSet(doc, xpath);

    if(appResult == NULL)
    {
        printf("App result is NULL\n");
        xmlFreeDoc(doc);
        return -1;
    }

    nodeset = appResult->nodesetval;

    for(i=0; i<nodeset->nodeNr; i++)
    {
        cur = nodeset->nodeTab[i];

        cur = cur->xmlChildrenNode;

        while(cur != NULL)
        {
            if(!xmlStrcmp(cur->name, (const xmlChar *)"name"))
            {
                printf("%s\n", ((char *)XML_GET_CONTENT(cur->xmlChildrenNode)));
            }
            else if(!xmlStrcmp(cur->name, (const xmlChar *)"url"))
            {
                printf("%s\n", ((char *)XML_GET_CONTENT(cur->xmlChildrenNode)));
            }

            cur = cur->next;
        }
    }

    xmlXPathFreeObject(appResult);

    return 0;
}

3.编译源码

$ gcc -o XPathXmlFile XPathXmlFile.c -I/usr/local/include/libxml2 -L/usr/local/lib -lxml2

4.运行及其结果

$ ./XPathXmlFile xpathtest.xml 
DEU-Antenne Bayern
http://mp3.webradio.antenne.de:80
DEU-Antenne Bayern
http://test