java - 如何在 Java 中解析 XML 元素根并选择它的某些值？

Question

我正在寻找一种实用的方法来解析 xml 根元素并从中获取一些值。我尝试了很多方法，但没有一个有效。

       DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

                Document doc = factory.newDocumentBuilder().parse(fileLoaded);

                Element root = null;

                NodeList list = doc.getChildNodes();
               System.out.println(list.toString());
                for (int i = 0; i < list.getLength(); i++) {
                  if (list.item(i) instanceof Element) {
                    root = (Element) list.item(i);
                    System.out.println(root.toString());
                    break;
                  }
                }
                root = doc.getDocumentElement();
              }

XML 文件:

    <planes_for_sale id="planeId" num="1452" name="boing">
    <ad>
      <year> 1977 </year>
      <make> test </make>
      <model> Skyhawk </model>
      <color> Light blue and white </color>
      <description> New paint, nearly new interior,
        685 hours SMOH, full IFR King avionics </description>
      <price> 23,495 </price>
      <seller phone = "555-222-3333"> Skyway Aircraft </seller>
      <location>
      <city> Rapid City, </city>
      <state> South Dakota </state>
  </location>

就我而言，我想从 planes_for_sale 根元素加载 id、num、name。

Answer 1

使用 XPath 提取属性值和元素内容。

    DocumentBuilder builder = DocumentBuilderFactory
                                 .newInstance()
                                 .newDocumentBuilder();

    Document doc = builder.parse(...);

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

    String id = xp.evaluate("planes_for_sale/@id", doc);
    String num = xp.evaluate("planes_for_sale/@num", doc);
    String name = xp.evaluate("planes_for_sale/@name", doc);

    System.out.println("id: " + id);
    System.out.println("num: " + num);
    System.out.println("name: " + name);

产品:

id: planeId
num: 1452
name: boing