零教程

使用DOM的步骤

以下是在使用DOM解析器解析文档使用的步骤。

• 导入XML相关的软件包。

• 创建DocumentBuilder

• 从文件或流创建一个文档

• 提取根元素

• 检查属性

• 检查子元素

导入XML相关的软件包

import org.w3c.dom.*
import javax.xml.parsers.*
import java.io.*

创建 DocumentBuilder

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

从文件或流创建一个文档

StringBuilder xmlStringBuilder = new StringBuilder()
xmlStringBuilder.append("<?xml version="1.0"?> <class> </class>")
ByteArrayInputStream input =  new ByteArrayInputStream(
   xmlStringBuilder.toString().getBytes("UTF-8"))
Document doc = builder.parse(input)

提取根元素

Element root = document.getDocumentElement()

检查属性

//returns specific attribute
getAttribute("attributeName") 
//returns a Map (table) of names/values
getAttributes() 

检查子元素

//returns a list of subelements of specified name
getElementsByTagName("subelementName") 
//returns a list of all child nodes
getChildNodes() 

演示示例

这是输入需要解析的 xml 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：

DomParserDemo.java

package com.yiibai.xml

import java.io.File
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

public class DomParserDemo {
   public static void main(String[] args){

      try {	
         File inputFile = new File("input.txt")
         DocumentBuilderFactory dbFactory 
            = DocumentBuilderFactory.newInstance()
         DocumentBuilder dBuilder = dbFactory.newDocumentBuilder()
         Document doc = dBuilder.parse(inputFile)
         doc.getDocumentElement().normalize()
         System.out.println("Root element :" 
            + doc.getDocumentElement().getNodeName())
         NodeList nList = doc.getElementsByTagName("student")
         System.out.println("----------------------------")
         for (int temp = 0 temp < nList.getLength() temp++) {
            Node nNode = nList.item(temp)
            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 (Exception e) {
         e.printStackTrace()
      }
   }
}

这将产生以下结果：

Root element :class
----------------------------

Current Element :student
Student roll no : 393
First Name : dinkar
Last Name : kad
Nick Name : dinkar
Marks : 85

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

Current Element :student
Student roll no : 593
First Name : jasvir
Last Name : singn
Nick Name : jazz
Marks : 90