我可以在 libxml2 中使用相对 XPath 表达式吗？

Question

我想知道是否可以在 libxml2 中使用相对 XPath 表达式。

这是来自 javax.xml.xpath API，我想使用 libxml2 做类似的事情:

Node widgetNode = (Node) xpath.evaluate(expression, document, XPathConstants.NODE);

With a reference to the element, a relative XPath expression can now written to select the child element:

XPath xpath = XPathFactory.newInstance().newXPath();
String expression = "manufacturer";
Node manufacturerNode = (Node) xpath.evaluate(expression, **widgetNode**, XPathConstants.NODE);

Answer 1

下面是一些代码示例:

xmlXPathContextPtr xpathCtx = xmlXPathNewContext(doc);

const xmlChar* xpathExpr = BAD_CAST "//column";
xmlXPathObjectPtr columnXPathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);


// Do whatever you want with your query here. Usually iterate over the result.
// Inside this iteration I do:

cur = columnNodes->nodeTab[i];

// Important part
xpathCtx->node = cur;

// After which you can do something like:
xmlXPathObjectPtr screenXPathObj = xmlXPathEvalExpression(BAD_CAST "screen", xpathCtx); 
xmlNodeSetPtr screenNodes = screenXPathObj->nodesetval;
for (int j = 0; j < screenNodes->nodeNr; j++) {
// You're now iterating over the <screen>s inside the curent <column>
}

希望这对某人有帮助。