從 XML 文件中讀取值

Question

我知道如何使用getelementbyTag在 Java 中讀取一個簡單的 XML 文件，但在這里我想從這里讀取 MAC 地址，即 Java 中的 01-0C-CD-01-00-34。

我正在嘗試使用getElementsByTagName("") ，但是我應該傳入什么參數來獲取type="MAC-Address"的元素？

<Address>
    <P type="MAC-Address"xsi:type="tP_MACAddress">010C-CD-01-00-34</P>
    <P type="VLAN-ID" xsi:type="tP_VLAN-ID">000</P>
    <P type="VLAN-PRIORITY" xsi:type="tP_VLAN-PRIORITY">4</P>
    <P type="APPID" xsi:type="tP_APPID">0001</P>
</Address>

我目前的代碼是：

public static void main(String argv[]) {
    try {
        File fXmlFile = new File("C:\\Users\\User\\Desktop\\Temp\\ReadXml\\staff.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(fXmlFile);

        doc.getDocumentElement().normalize();

        NodeList nList = doc.getElementsByTagName("Address");

        for (int temp = 0; temp < nList.getLength(); temp++) {
            Node nNode = nList.item(temp);

            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                Element eElement = (Element) nNode;
                System.out.println("MAC: " + eElement.getElementsByTagName("").item(0).getTextContent());
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Answer 1

您可以使用 xpath 查找 xml 文檔的特定部分

        File fXmlFile = new File("C:\\Users\\User\\Desktop\\Temp\\ReadXml\\staff.xml");
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
        Document doc = dBuilder.parse(fXmlFile);

        // Create XPathExpression
        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();
        XPathExpression expr =
                xpath.compile("/Address/P[@type='MAC-Address']/text()");
        // evaluate the Xpath and return result as a string.
        String mac = (String) expr.evaluate(doc, XPathConstants.STRING);

        System.out.println("MAC: " + mac);

Xpath 類都來自java.xml.xpath包

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

如果你想導航節點，你可以。 您不需要規范化文檔，但在查找節點時確實需要使用文檔元素而不僅僅是文檔。 您可以獲取所有“P”標簽並查找 MAC 地址。 就像是：

        NodeList nList = doc.getDocumentElement().getElementsByTagName("P");

        for (int temp = 0; temp < nList.getLength(); temp++) {
            Node nNode = nList.item(temp);

            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
                Element eElement = (Element) nNode;
                if ("MAC-Address".equals(eElement.getAttribute("type"))) {
                    System.out.println("MAC: " + eElement.getTextContent());
                }
            }
        }