使用document解析xml文件

在慕课上课时，看到可以使用document来解析xml文件，把上课的代码放出来，先记录一下。

大概步骤如下：

1.使用DocumentBuilderFactory 创建对象后再创建DocumentBuilder对象，再根据DocumentBuilder对象创建Document得对象并导入需要解析的xml文件
2.通过document.getChildNodes() 获取一级节点对象NodeList对象
3.然后遍历获取2级节点对象，然后继续遍历
4.得到最后得文本对象时，就可以输出文本名称和值了

xml文件（共三个节点）如下：

<?xml version="1.0" encoding="UTF-8"?>
<users>
    <user id="0">
        <name>Mary</name>
        <age>23</age>
        <sex>Female</sex>
    </user>
    <user id="1">
        <name>Mike</name>
        <age>24</age>
        <sex>Male</sex>
    </user>
    <user id="2">
        <name>Alice</name>
        <age>23</age>
        <sex>Female</sex>
    </user>
    <user id="3">
        <name>Tom</name>
        <age>24</age>
        <sex>Male</sex>
    </user>
</users>

package xml.dom;

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 DomReader 
{
	public static void main(String[] a)
	{
		recursiveTraverse(); //自上而下进行访问
		System.out.println("========华丽丽的分割线==========");
		traverseBySearch();    //根据名称进行搜索		
	}
	
    public static void recursiveTraverse()
    {
    	try 
    	{
    		//采用Dom解析xml文件
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document document = db.parse("users.xml");
            
            //获取所有的一级子节点
            NodeList usersList = document.getChildNodes();
            System.out.println(usersList.getLength());  //1  
            
            for (int i = 0; i < usersList.getLength(); i++) 
            {
                Node users = usersList.item(i);         //1  users 
                
                NodeList userList = users.getChildNodes(); //获取二级子节点user的列表
                System.out.println("==" + userList.getLength()); //9
                
                for (int j = 0; j < userList.getLength(); j++) //9
                {
                    Node user = userList.item(j);
                    if (user.getNodeType() == Node.ELEMENT_NODE)
                    {
                    	 NodeList metaList = user.getChildNodes();
                         System.out.println("====" + metaList.getLength()); //7
                         
                         for (int k = 0; k < metaList.getLength(); k++) //7
                         {
                         	//到最后一级文本
                        	Node meta = metaList.item(k);
                        	if (meta.getNodeType() == Node.ELEMENT_NODE)
                        	{
                        		System.out.println(metaList.item(k).getNodeName() 
                        				+ ":" + metaList.item(k).getTextContent());
                        	}                                                              
                         }                    
                         System.out.println();
                    }                   
                }
            }            
        } catch (Exception e) {
            e.printStackTrace();
        } 
    }   
    
    public static void traverseBySearch()
    {
    	try 
    	{
    		//采用Dom解析xml文件
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document document = db.parse("users.xml");
            
            Element rootElement = document.getDocumentElement();         

            NodeList nodeList = rootElement.getElementsByTagName("name"); 
            if(nodeList != null) 
            { 
               for (int i = 0 ; i < nodeList.getLength(); i++) 
               { 
                  Element element = (Element)nodeList.item(i);                  
                  System.out.println(element.getNodeName() + " = " + element.getTextContent());
               } 
            }             
        } catch (Exception e) {
            e.printStackTrace();
        } 	
    }       
}

• 然后写使用document来写xml文件步骤也是差不多，多使用了一个transform得jar包，给出代码如下：

package xml.dom;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class DomWriter {

	public static void main(String[] args) {
		
		
		try {
			DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
			DocumentBuilder dbBuilder = dbFactory.newDocumentBuilder();
			
			//新创建一个Document节点
			Document document = dbBuilder.newDocument();
			if (document != null) 
			{
				Element docx = document.createElement("document");	//都是采用Document创建元素		
				Element element = document.createElement("element");
				element.setAttribute("type", "paragraph"); 
				element.setAttribute("alignment", "left"); //element增加2个属性
				
				Element object = document.createElement("object");
				object.setAttribute("type", "text");
				
				Element text = document.createElement("text");
				text.appendChild(document.createTextNode("abcdefg")); //给text节点赋值
				Element bold = document.createElement("bold");
				bold.appendChild(document.createTextNode("true"));    //给bold节点赋值
				
				object.appendChild(text);      //把text节点挂在object下
				object.appendChild(bold);      //把bold节点挂在object下
				element.appendChild(object);   //把object节点挂在element下
				docx.appendChild(element);	   //把element节点挂在docx下		
				document.appendChild(docx);    //把docx挂在document下
				
				TransformerFactory transformerFactory = TransformerFactory.newInstance();
				Transformer transformer = transformerFactory.newTransformer();
				DOMSource source = new DOMSource(document);
				
				//定义目标文件
				File file = new File("dom_result.xml");
				StreamResult result = new StreamResult(file);
		 	 
				//将xml内容写入到文件中
				transformer.transform(source, result);
				
				System.out.println("write xml file successfully");
			}
		} catch (Exception e) {
			e.printStackTrace();
		}		
	}	
}

共勉！