运用java读取xml文件---DOM 解析

读取本地的xml文件，通过DOM进行解析，DOM解析的特点就是把整个xml文件装载入内存中，形成一颗DOM树形结构，树结构是方便遍历和和操纵。

DOM解析的特性就是读取xml文件转换为 dom树形结构，通过节点进行遍历。

这是W3c关于节点的概念

如果xml中包含有大量的数据，由于dom一次性把xml装入内存中的特性，所以dom不适合于包含大量数据的xml解析。当包含有大量xml的时候，用SAX进行解析比较节省内存。

下面是一个运用DOM进行解析xml文件的例子：

xml文件结构如下：

  
    
    Giada De Laurentiis
    2005
    30.00
  
  
    
    J K. Rowling
    2005
    29.99
  
  
    
    James McGovern
    2003
    49.99
  
  
    
    Erik T. Ray
    2003
    39.95
  

创建解析xml的类如下：

package xml.dom;

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

public class ReadXmlFile {
	
   public static void main(String[] args)  {
	   
	   try{
		   
		   File  xmlFile = new File("src/resource/book.xml");
		   
		   DocumentBuilderFactory  builderFactory =  DocumentBuilderFactory.newInstance();
		   
		   DocumentBuilder   builder = builderFactory.newDocumentBuilder();
		   
		   Document  doc = builder.parse(xmlFile);
		   
		   doc.getDocumentElement().normalize();
		   
		   System.out.println("Root  element: "+doc.getDocumentElement().getNodeName());
		   
		   NodeList  nList = doc.getElementsByTagName("book");
		   
		   for(int  i = 0 ; i

解析结果：

Root  element: bookstore
Node name: book
----------------------------
book category: cooking
title name: Everyday Italian
author name: Giada De Laurentiis
year :2005
price : 30.00
-------------------------
Node name: book
----------------------------
book category: children
title name: Harry Potter
author name: J K. Rowling
year :2005
price : 29.99
-------------------------
Node name: book
----------------------------
book category: web
title name: XQuery Kick Start
author name: James McGovern
year :2003
price : 49.99
-------------------------
Node name: book
----------------------------
book category: web
title name: Learning XML
author name: Erik T. Ray
year :2003
price : 39.95
-------------------------

以上是通过name获得对应的值，

下面利用循环节点的方式输出：

循环节点输出方式的代码如下：

package xml.dom;

import java.io.File;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class ReadXmlFile2 {
	
 public static void main(String[] args) {
   try{
		   
		   File  xmlFile = new File("src/resource/book.xml");
		   
		   DocumentBuilderFactory  builderFactory =  DocumentBuilderFactory.newInstance();
		   
		   DocumentBuilder   builder = builderFactory.newDocumentBuilder();
		   
		   Document  doc = builder.parse(xmlFile);
		   
		   doc.getDocumentElement().normalize();
		   
		   System.out.println("Root  element: "+doc.getDocumentElement().getNodeName());
		   
		   
		   if(doc.hasChildNodes()){
			   
			   printNode(doc.getChildNodes());
		   }
   }catch(Exception  e){
	   
	   e.printStackTrace();
	   
   }
 
 }
 
 public  static  void  printNode(NodeList nodeList){
	 System.out.println("------------------------");
	// System.out.println(nodeList.getLength());
	 for(int i = 0;  i

输出结果如下：

Root  element: bookstore
------------------------
node name: bookstore
node value: 
  
    Everyday Italian
    Giada De Laurentiis
    2005
    30.00
  
  
    Harry Potter
    J K. Rowling
    2005
    29.99
  
  
    XQuery Kick Start
    James McGovern
    2003
    49.99
  
  
    Learning XML
    Erik T. Ray
    2003
    39.95
  

------------------------
node name: book
node value: 
    Everyday Italian
    Giada De Laurentiis
    2005
    30.00
  
node name category
node value cooking
------------------------
node name: title
node value: Everyday Italian
node name lang
node value en
------------------------
node name: author
node value: Giada De Laurentiis
------------------------
node name: year
node value: 2005
------------------------
node name: price
node value: 30.00
------------------------
node name: book
node value: 
    Harry Potter
    J K. Rowling
    2005
    29.99
  
node name category
node value children
------------------------
node name: title
node value: Harry Potter
node name lang
node value en
------------------------
node name: author
node value: J K. Rowling
------------------------
node name: year
node value: 2005
------------------------
node name: price
node value: 29.99
------------------------
node name: book
node value: 
    XQuery Kick Start
    James McGovern
    2003
    49.99
  
node name category
node value web
------------------------
node name: title
node value: XQuery Kick Start
node name lang
node value en
------------------------
node name: author
node value: James McGovern
------------------------
node name: year
node value: 2003
------------------------
node name: price
node value: 49.99
------------------------
node name: book
node value: 
    Learning XML
    Erik T. Ray
    2003
    39.95
  
node name category
node value web
node name cover
node value paperback
------------------------
node name: title
node value: Learning XML
node name lang
node value en
------------------------
node name: author
node value: Erik T. Ray
------------------------
node name: year
node value: 2003
------------------------
node name: price
node value: 39.95
------------------------

关于节点的问题：

 
    
    Giada De Laurentiis
    2005
    30.00
  

对于 book应用：doc.getChildNodes() 得到一个NodeList其中NodeList的长度为9

9个节点分别如下：

title节点

lang节点  

Everyday节点

 author节点 

Giada De Laurentiis节点

 year节点

 2005节点

 price节点

 30.00节点