解析XML文档（Parse XML Document）

使用JDOM的步骤

以下是使用JDOM Parser解析文档时使用的步骤。

• 导入与XML相关的包。
• 创建一个SAXBuilder
• 从文件或流创建文档
• 提取根元素
• 检查属性
• 检查子元素

Import XML-related packages

import java.io.*;
import java.util.*;
import org.jdom2.*;

创建一个DocumentBuilder (Create a DocumentBuilder)

SAXBuilder saxBuilder = new SAXBuilder();

从文件或流创建文档

File inputFile = new File("input.txt");
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(inputFile);

提取根元素

Element classElement = document.getRootElement();

检查属性 (Examine attributes)

//returns specific attribute
getAttribute("attributeName"); 

检查子元素 (Examine sub-elements)

//returns a list of subelements of specified name
getChildren("subelementName"); 
//returns a list of all child nodes
getChildren(); 
//returns first child node
getChild("subelementName"); 

例子 (Demo Example)

这是我们需要解析的输入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>

DomParserDemo.java

import java.io.File;
import java.io.IOException;
import java.util.List;
import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;
public class JDomParserDemo {
   public static void main(String[] args) {
      try {
         File inputFile = new File("input.txt");
         SAXBuilder saxBuilder = new SAXBuilder();
         Document document = saxBuilder.build(inputFile);
         System.out.println("Root element :" + document.getRootElement().getName());
         Element classElement = document.getRootElement();
         List<Element> studentList = classElement.getChildren();
         System.out.println("----------------------------");
         for (int temp = 0; temp < studentList.size(); temp++) {    
            Element student = studentList.get(temp);
            System.out.println("\nCurrent Element :" 
               + student.getName());
            Attribute attribute =  student.getAttribute("rollno");
            System.out.println("Student roll no : " 
               + attribute.getValue() );
            System.out.println("First Name : "
               + student.getChild("firstname").getText());
            System.out.println("Last Name : "
               + student.getChild("lastname").getText());
            System.out.println("Nick Name : "
               + student.getChild("nickname").getText());
            System.out.println("Marks : "
               + student.getChild("marks").getText());
         }
      } catch(JDOMException e) {
         e.printStackTrace();
      } catch(IOException ioe) {
         ioe.printStackTrace();
      }
   }
}

这会产生以下结果 -

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