java读取xml数据_java如何从xml文件中读取一个值

Java可以使用DOM、SAX、JDOM等方式来读取XML文件中的数据。以下是使用DOM方式读取XML文件中某个节点值的示例代码：

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;

public class ReadXML {
   public static void main(String argv[]) {

      try {
         File inputFile = new File("input.xml");
         DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
         DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
         Document doc = dBuilder.parse(inputFile);
         doc.getDocumentElement().normalize();

         NodeList nList = doc.getElementsByTagName("book");
         Node nNode = nList.item(0);
         Element eElement = (Element) nNode;

         String title = eElement.getElementsByTagName("title").item(0).getTextContent();
         System.out.println("Book title : " + title);
      } catch (Exception e) {
         e.printStackTrace();
      }
   }
}

这段代码会读取名为`input.xml`的XML文件中第一个`book`节点的`title`子节点的值，并输出在控制台上。需要注意的是，此示例中的XML文件结构为：

<?xml version="1.0"?>
<catalog>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
      <genre>Computer</genre>
      <price>44.95</price>
      <publish_date>2000-10-01</publish_date>
      <description>An in-depth look at creating applications 
      with XML.</description>
   </book>
   <book id="bk102">
      <author>Ralls, Kim</author>
      <title>Midnight Rain</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-12-16</publish_date>
      <description>A former architect battles corporate zombies, 
      an evil sorceress, and her own childhood to become queen 
      of the world.</description>
   </book>
</catalog>

如果想要读取其他节点的值，可以将示例代码中的`getElementsByTagName`和`getElementsByTagName`方法中的参数值进行相应修改。