xpathforxmlfile.cpp

xml 用xpath读文件使用范例 包括解析等

/********************************************************************  
    created:    2007/11/15  
    created:    15:11:2007   16:01  
    filename:   XpathForXmlFile.cpp  
    author:     Wang xuebin   
    depend:     libxml2.lib  
    build:      nmake TARGET_NAME=XPathForXmlFile  
      
    purpose:    使用XPATH查找xml文档中的节点  
*********************************************************************/   
   
#include <LIBXML parser.h>    
#include <LIBXML xpath.h>    
#include <IOSTREAM.H>    
   
xmlXPathObjectPtr get_nodeset(xmlDocPtr doc, const xmlChar *szXpath)    
{   
    xmlXPathContextPtr context;     //XPATH上下文指针    
    xmlXPathObjectPtr result;       //XPATH对象指针，用来存储查询结果    
       
    context = xmlXPathNewContext(doc);      //创建一个XPath上下文指针    
    if (context == NULL)    
    {      
        printf("context is NULL\n");   
        return NULL;    
    }   
       
    result = xmlXPathEvalExpression(szXpath, context); //查询XPath表达式，得到一个查询结果    
    xmlXPathFreeContext(context);               //释放上下文指针    
    if (result == NULL)    
    {   
        printf("xmlXPathEvalExpression return NULL\n");    
        return NULL;     
    }   
       
    if (xmlXPathNodeSetIsEmpty(result->nodesetval))   //检查查询结果是否为空    
    {   
        xmlXPathFreeObject(result);   
        printf("nodeset is empty\n");   
        return NULL;   
    }   
       
    return result;     
}   
   
int main(int argc, char* argv[])   
{   
    xmlDocPtr doc = NULL;            //定义解析文档指针     
    xmlNodePtr curNode = NULL;       //定义结点指针(你需要它为了在各个结点间移动)     
   
    char *szDocName = NULL;   
    if (argc <= 1)     
    {   
        printf("Usage: %s docname\n", argv[0]);   
        return(0);   
    }   
    szDocName = argv[1];   
   
    doc = xmlReadFile(szDocName,"GB2312",XML_PARSE_RECOVER);  //解析文件     
       
    if (NULL == doc)    
    {      
        fprintf(stderr,"Document not parsed successfully. \n");        
        return -1;    
    }    
       
    xmlChar *szXpath =BAD_CAST ("/root/node2[@attribute='yes']");    
    xmlXPathObjectPtr app_result = get_nodeset(doc,szXpath);  //查询并得到结果    
       
    if (NULL == app_result)    
    {   
        printf("app_result is NULL\n");    
        return -1;   
    }   
    xmlChar *szValue = NULL;   
    if(app_result)    
    {   
        xmlNodeSetPtr nodeset = app_result->nodesetval;   
        for (int i = 0; i < nodeset->nodeNr; i++)    
        {   
            curNode = nodeset->nodeTab[i];       
            if(curNode != NULL)    
            {   
                szValue = xmlGetProp(curNode,BAD_CAST "attribute");   
                if (szValue != NULL)    
                {   
                    printf("attribute = %s\n", szValue);   
                    xmlFree(szValue);   
                }   
                   
                szValue = xmlNodeGetContent(curNode);   
                if (szValue != NULL)    
                {   
                    printf("content = %s\n", szValue);   
                    xmlFree(szValue);   
                }   
            }   
        }   
        xmlXPathFreeObject (app_result);   
    }   
    xmlFreeDoc(doc);   
    return 0;   
}