java xpath返回意外值

Question

I'm builind an application which shows a map with the google api. Using the user input address, I query the API for directions to a destination. The API returns me a XML response which I parse to build my directions objects and show informations to the user.

Everything works but some of my xpath.evaluate() use do not work as I expect. For example this response :

Google Maps Response

When I use :

NodeList legList = (NodeList) xpath.evaluate("//route/leg",
                    response, XPathConstants.NODE);

Even //leg should do the job right?

When I do a legList.getLength(), it gives me 23 but there are only two leg in the response. Do you know why this strange behavior is happening? I read about XML Namespace but I still don't know what to do, should I specidfy a namespace even if the answer doesn't contain any, and if yes, why do I have to?

Answer 1

如果你想要NodeList使用XPathConstants.NODESET而不是XPathConstants.NODE （请点击此处查看映射： http ： //docs.oracle.com/javase/6/docs/api/javax/xml/xpath/XPathConstants.html#NODESET ） 像这样：

NodeList legList = (NodeList) xpath.evaluate("//route/leg", response, XPathConstants.NODESET);

Answer 2

You need to use

    NodeList legList = (NodeList) xpath.evaluate(expr,
            xml, XPathConstants.NODESET);

Answer 3

try this code.

NodeList legList = (NodeList) xpath.evaluate("/route/leg",
                response, XPathConstants.NODESET);

NODESET is return the NodeList while XPathConstants.NODE is return single Object.