java - 使用Java获取XML中标签的属性值

Question

我正在尝试用 Java 将 text2 替换为其他内容。我在使用此代码时遇到问题:

try {
    String filepath = "c:\\path\\file.xml";
    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
    Document doc = docBuilder.parse(filepath);
    Node a = doc.getFirstChild();
    Node b = doc.getElementsByTagName("b").item(0);
    NodeList list = b.getChildNodes();

    for (int i = 0; i < list.getLength(); i++) {

               Node node = list.item(i);
       if ("c".equals(node.getNodeName())) { //Want to add '&& attribute value of key is 4'
        node.setTextContent("new text");
       }

    }

    // write the content into xml file
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(doc);
    StreamResult result = new StreamResult(new File(filepath));
    transformer.transform(source, result);

    System.out.println("Done");

   } catch (ParserConfigurationException pce) {
    pce.printStackTrace();
   } catch (TransformerException tfe) {
    tfe.printStackTrace();
   } catch (IOException ioe) {
    ioe.printStackTrace();
   } catch (SAXException sae) {
    sae.printStackTrace();
   }

XML 如下所示:

<?xml version="1.0" encoding="utf-8">
<a>
    <b id="1">
        <c key="3">text1</c>
        <c key="4">text2</c> //Replace this
    </b>
    <b id="2">
        <c key="5">text3</c>
        <c key="6">text4</c>
    </b>
</a>

我从这里的指南中得到了这个:https://www.mkyong.com/java/how-to-modify-xml-file-in-java-dom-parser/ 并且目前也在这一行给我一个错误 transformer.transform(source, result);

Answer 1

对于像这样简单的事情，您可以使用 XPath，并使用表达式 "//c[@key='4']" ，这意味着:查找 <c>具有名为 key 的属性的任何级别的元素值为4 .

Document doc = DocumentBuilderFactory.newInstance()
                                     .newDocumentBuilder()
                                     .parse("file.xml");

Node c4 = (Node) XPathFactory.newInstance()
                             .newXPath()
                             .evaluate("//c[@key='4']", doc, XPathConstants.NODE);
c4.setTextContent("new text");

TransformerFactory.newInstance()
                  .newTransformer()
                  .transform(new DOMSource(doc),
                             new StreamResult(System.out));

输出

<?xml version="1.0" encoding="utf-8" standalone="no"?><a>
    <b id="1">
        <c key="3">text1</c>
        <c key="4">new text</c>
    </b>
    <b id="2">
        <c key="5">text3</c>
        <c key="6">text4</c>
    </b>
</a>