# Java JDOM解析器 - 解析XML文档 - Java XML教程
## 使用JDOM的步骤
以下是解析时使用JDOM解析器文档的步骤。
* 导入XML相关的软件包
* 创建一个SAXBuilder
* 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 java.io.*;
import java.util.*;
import org.jdom2.*;
```
**创建DocumentBuilder**
```
SAXBuilder saxBuilder = new SAXBuilder();
```
**从文件或流创建一个文档**
```
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**
```
//returns specific attribute
getAttribute("attributeName");
```
**检查子元素**
```
//returns a list of subelements of specified name
getChildren("subelementName");
//returns a list of all child nodes
getChildren();
//returns first child node
getChild("subelementName");
```
## 演示示例
这是输入需要解析xml文件：
```
dinkar
kad
dinkar
85
Vaneet
Gupta
vinni
95
jasvir
singn
jazz
90
```
**演示示例：**
_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 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
```