Xpath Java 无法获取 URL

Question

Xpath 似乎不起作用。我已经尝试了一些东西，但似乎没有任何效果。我究竟做错了什么？DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();factory.setNamespaceAware(true);DocumentBuilder builder = factory.newDocumentBuilder();Document doc = builder.parse(new InputSource(new StringReader(result)));XPathFactory xPathfactory = XPathFactory.newInstance();XPath xpath = xPathfactory.newXPath();XPathExpression expr = xpath.compile("//cm:URL/@value");String msg = expr.evaluate(doc, XPathConstants.STRING).toString();       logger.debug(msg);我拥有的 XML 如下所示：<ItemXML xmlns="http://www.ibm.com/xmlns/db2/cm/beans/1.0/schema" xmlns:ns2="http://www.ibm.com/xmlns/db2/cm/api/1.0/schema">    <DOCUMENTS SCA_DATE="#" SCA_NR="#" cm:PID="#" xmlns:cm="http://www.ibm.com/xmlns/db2/cm/api/1.0/schema" xmlns:ns1="http://www.ibm.com/xmlns/db2/cm/beans/1.0/schema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">        <cm:properties type="#">            <cm:lastChangeUserid value="#"/>            <cm:lastChangeTime value="#"/>            <cm:createUserid value="#"/>            <cm:createTime value="#"/>            <cm:semanticType value="#"/>            <cm:ACL name="#"/>            <cm:lastOperation name="#" value="#"/>        </cm:properties>        <ns1:CONTRACTS AM="#"/>        <ns1:BASE cm:PID="#" cm:partNumber="#">            <cm:properties type="item" xsi:type="#">                <cm:lastChangeUserid value="#"/>                <cm:lastChangeTime value="#"/>                <cm:createUserid value="#"/>                <cm:createTime value="#"/>                <cm:semanticType value="#"/>                <cm:ACL name="#"/>                <cm:lastOperation name="#" value="#"/>            </cm:properties>我希望将cm:URL --> https://testurl.com的值保存为字符串。重要提示：无论 xml 结构如何，Xpath 都应该找到该值。

Answer 1

在不使用 XPath 的情况下，您可以：

NodeList elementsByTagName = doc.getDocumentElement().getElementsByTagName("cm:URL");

System.out.println("result: " + elementsByTagName.item(0).getAttributes().getNamedItem("value").getNodeValue());

Answer 2

使用他的解决方案，我尝试了它的工作

import java.io.File;

import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.xpath.XPathExpressionException;

import org.w3c.dom.Document;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

public class XpathTester {

    public static void main(String[] args) throws XPathExpressionException, ParserConfigurationException, SAXException, IOException {

        File inputFile = new File("C:\\Users\\Arvind.Carpenter\\Desktop\\input.txt");

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        factory.setNamespaceAware(true);

        DocumentBuilder builder = factory.newDocumentBuilder();

        Document doc = builder.parse(inputFile);

        doc.getDocumentElement().normalize();

        NodeList elementsByTagName = doc.getDocumentElement().getElementsByTagName("cm:URL");

        //you can iterate over this node list and get all the URL i am printing first one

        System.out.println("result: " + elementsByTagName.item(0).getAttributes().getNamedItem("value").getNodeValue()); 

    }

}

Answer 3

以下行有问题：-

Document doc = builder.parse(new InputSource(new StringReader(result)));

我尝试打印文档，它给我的输出为 [#document: null]，你可以先尝试在控制台中打印文档并让我知道它是否不为空。