如何获得特定的XML元素参数值？

Question

我开始解析xml文档并提出问题:如何在Java上获得特定的XML元素参数值？

XML文档：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<data>
<keyword name="text123">
    <profile num="1">
        <url>http://www.a.com</url>
        <field-1 param="">text</field-1>
        <filed-2 param="">text</field-2>
    </profile>
    <profile num="2">
        <url>http://www.b.com</url> 
        <field-1 param="">text</field-1>
        <filed-2 param="">text</field-2>
    </profile>
</keyword>
<keyword name="textabc123">
    <profile num="1">
        <url>http://www.1a.com</url>
        <field-1 param="">text</field-1>
        <filed-2 param="">text</field-2>
    </profile>
    <profile num="2">
        <url>http://www.1b.com</url> 
        <field-1 param="">text</field-1>
        <filed-2 param="">text</field-2>
    </profile>
</keyword>
</data>

我在Java上编写的代码：

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
File xml_file=new File("file.xml");
if (xml_file.isFile() && xml_file.canRead()) {
 Document doc = builder.parse(xml_file);
 Element root = doc.getDocumentElement();
 NodeList nodel = root.getChildNodes();
 for (int a = 0; a < nodel.getLength(); a++) {
  String data = /* code i don't know to write*/
  System.out.println(data);
 }
} else {}

我想输出到控制台元素“关键字”参数"name“值：

text123

和

text123abc

帮帮忙，谢谢。

Answer 1

Node node = nodel.item(a);
if(node instanceof Element) {
  data = ((Element)node).getAttribute("name");
  System.out.println(data);
}

Answer 2

您可以使用XPath

InputStream is = getClass().getResourceAsStream("somefile.xml");
DocumentBuilderFactory xmlFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = xmlFactory.newDocumentBuilder();
Document xmlDoc = docBuilder.parse(is);
XPathFactory xpathFact = XPathFactory.newInstance();
XPath xpath = xpathFact.newXPath();

String text123 = (String) xpath.evaluate("/data/keyword[1]/@name", xmlDoc, XPathConstants.STRING);
String textabc123 = (String) xpath.evaluate("/data/keyword[2]/@name", xmlDoc, XPathConstants.STRING);

Answer 3

节点列表包含节点，这些节点实际上是子接口(元素、文本等)的实例。

因此，这一守则应适用于：

Node node = nodel.item(a);
if (node instanceof Element) {
    Element e = (Element) node;
    System.out.println(e.getAttribute("name");
}