java - JDOM2 和 XPath

Question

当我运行以下

XPathFactory xpathFactory = XPathFactory.instance();
XPathExpression<Double> query =
xpathFactory.compile("count(1)", Filters.fdouble());
List<Double> result = query.evaluate(new Element("test"));

但评估失败：

无法计算表达式。查看原因 原因：功能：计数

这是一个有点胡说八道的例子，但我想要一些自包含的东西。这有什么问题？

Answer 1

如果你想计算test元素的数量，试试这个；

Element root = new Element("test");
Document doc = new Document(root);

XPathFactory xpathFactory = XPathFactory.instance();
XPathExpression<Double> query = xpathFactory.compile("count(//test)", Filters.fdouble());
List<Double> result = query.evaluate(doc);