用libxml2按路径获取属性值？

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

int main() {
    xmlDocPtr doc;
    xmlXPathContextPtr xpathCtx;
    xmlXPathObjectPtr xpathObj;

    // 加载XML文档
    doc = xmlParseFile("example.xml");
    if (doc == NULL) {
        printf("Failed to parse XML document.\n");
        return 1;
    }

    // 创建XPath上下文
    xpathCtx = xmlXPathNewContext(doc);
    if (xpathCtx == NULL) {
        printf("Failed to create XPath context.\n");
        xmlFreeDoc(doc);
        return 1;
    }

    // 执行XPath查询
    xpathObj = xmlXPathEvalExpression((xmlChar*)"//book[@id='123']/@title", xpathCtx);
    if (xpathObj == NULL) {
        printf("Failed to evaluate XPath expression.\n");
        xmlXPathFreeContext(xpathCtx);
        xmlFreeDoc(doc);
        return 1;
    }

    // 获取属性值
    if (xpathObj->nodesetval->nodeTab[0]->type == XML_ATTRIBUTE_NODE) {
        xmlChar* value = xmlNodeListGetString(doc, xpathObj->nodesetval->nodeTab[0]->children, 1);
        printf("Attribute value: %s\n", value);
        xmlFree(value);
    }

    // 释放资源
    xmlXPathFreeObject(xpathObj);
    xmlXPathFreeContext(xpathCtx);
    xmlFreeDoc(doc);

    return 0;
}