零教程

演示示例

这是我们需要查询输入的文本文件：

<?xml version="1.0"?>
<class>
   <student rollno="393">
      <firstname>dinkar</firstname>
      <lastname>kad</lastname>
      <nickname>dinkar</nickname>
      <marks>85</marks>
   </student>
   <student rollno="493">
      <firstname>Vaneet</firstname>
      <lastname>Gupta</lastname>
      <nickname>vinni</nickname>
      <marks>95</marks>
   </student>
   <student rollno="593">
      <firstname>jasvir</firstname>
      <lastname>singn</lastname>
      <nickname>jazz</nickname>
      <marks>90</marks>
   </student>
</class>

%uA0

演示示例：

XPathParserDemo.java

package com.yiibai.xml

import java.io.File
import java.io.IOException

import javax.xml.parsers.DocumentBuilderFactory
import javax.xml.parsers.DocumentBuilder
import javax.xml.parsers.ParserConfigurationException
import javax.xml.xpath.XPath
import javax.xml.xpath.XPathConstants
import javax.xml.xpath.XPathExpressionException
import javax.xml.xpath.XPathFactory

import org.w3c.dom.Document
import org.w3c.dom.NodeList
import org.w3c.dom.Node
import org.w3c.dom.Element
import org.xml.sax.SAXException

public class XPathParserDemo {
   public static void main(String[] args) {
      try {
         File inputFile = new File("input.txt")
         DocumentBuilderFactory dbFactory 
            = DocumentBuilderFactory.newInstance()
         DocumentBuilder dBuilder

         dBuilder = dbFactory.newDocumentBuilder()

         Document doc = dBuilder.parse(inputFile)
         doc.getDocumentElement().normalize()

         XPath xPath =  XPathFactory.newInstance().newXPath()

         String expression = "/class/student[@rollno=&apos493&apos]"	        
         NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(doc, XPathConstants.NODESET)
         for (int i = 0 i < nodeList.getLength() i++) {
            Node nNode = nodeList.item(i)
            System.out.println("\nCurrent Element :" 
               + nNode.getNodeName())
            if (nNode.getNodeType() == Node.ELEMENT_NODE) {
               Element eElement = (Element) nNode
               System.out.println("Student roll no : " 
                  + eElement.getAttribute("rollno"))
               System.out.println("First Name : " 
                  + eElement
                     .getElementsByTagName("firstname")
                     .item(0)
                     .getTextContent())
               System.out.println("Last Name : " 
                  + eElement
                     .getElementsByTagName("lastname")
                     .item(0)
                     .getTextContent())
               System.out.println("Nick Name : " 
                  + eElement
                     .getElementsByTagName("nickname")
                     .item(0)
                     .getTextContent())
               System.out.println("Marks : " 
                  + eElement
                     .getElementsByTagName("marks")
                     .item(0)
                     .getTextContent())
            }
         }
      } catch (ParserConfigurationException e) {
         e.printStackTrace()
      } catch (SAXException e) {
         e.printStackTrace()
      } catch (IOException e) {
         e.printStackTrace()
      } catch (XPathExpressionException e) {
         e.printStackTrace()
      }
   }
}

这将产生以下结果:

Current Element :student
Student roll no : 493
First Name : Vaneet
Last Name : Gupta
Nick Name : vinni
Marks : 95