Question

对于下面的xml文件，我想检索对应于lat = 53.0337395的id的值，而在xml中有两个id，其中lat = 53.0337395。如下所示，为了实现这一点，我编写了以下代码，但在运行时我收到了#NUMBER cannt be converted into a nodelist

请让我知道如何解决它

String expr0 = "count(//node[@lat=53.0337395]//@id)";
xPath.compile(expr0);
NodeList nodeList = (NodeList) xPath.compile(expr0).evaluate(document, 
XPathConstants.NODESET);
System.out.println(nodeList.getLength());

XML ：

<?xml version='1.0' encoding='utf-8' ?>
<osm>
<node id="25779111" lat="53.0334062" lon="8.8461545"/>
<node id="25779112" lat="53.0338904" lon="8.846314"/>
<node id="25779119" lat="53.0337395" lon="8.8489255"/>
<tag k="maxspeed" v="30"/>  
<tag k="maxspeed:zone" v="yes"/>
<node id="25779111" lat="53x.0334062" lon="8x.8461545"/>
<node id="25779112" lat="53x.0338904" lon="8x.846314"/>
<node id="257791191" lat="53.0337395" lon="8x.8489255"/>
<tag k="maxspeed" v="30x"/> 
<tag k="maxspeed:zone" v="yes"/>
</osm>

Answer 1

如果您想获取节点列表（count()将返回一个数字，而不是列表），我不确定您使用count()的原因。试试这个：

String expr0 = "/osm/node[@lat=53.0337395]/@id";
NodeList nodeList = (NodeList) xPath.compile(expr0).evaluate(document,
                                                             XPathConstants.NODESET);
System.out.println(nodeList.getLength());

以下是使用XML文件作为输入的完整可编译示例：

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

public class IdFinder
{
    public static void main(String[] args)
            throws Exception
    {
        File fXmlFile = new File("C:/Users/user2121/osm.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document document = dBuilder.parse(fXmlFile);

        XPath xPath = XPathFactory.newInstance().newXPath();

        String expr0 = "/osm/node[@lat=53.0337395]/@id";
        NodeList nodeList = (NodeList) xPath.compile(expr0).evaluate(document, XPathConstants.NODESET);

        System.out.println("Matches: " + nodeList.getLength());
        for (int i = 0; i < nodeList.getLength(); i++) {
            System.out.println(nodeList.item(i).getNodeValue());
        }
    }
}

这个输出是：

Matches: 2
25779119
257791191

如何在nodelist中检索属性值

1 个答案: