用JAXP的dom方式解析XML文件

用JAXP的dom方式解析XML文件，实现增删改查操作

dom方式解析XML原理

XML文件

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<class>
    <student>
        <name>张三</name>
        <sid>111111</sid>
    </student>
    <student>
        <name>李四</name>
        <sid>222222</sid>
    </student>
</class>

Java代码

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;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

public class JaxpDom {
    static Document document;
    public static void main(String[] args) throws Exception {
        add();//在第一个学生信息里增加一个性别标签<sex>男<sex>
        //delete();//删除上个方法新建的sex标签
        //modify();//将第二个学生的姓名改为王五
        //select();//查询第一个name标签的内容
        //selectAll();//遍历出所有的标签
    }

    //在第一个学生信息里增加一个性别标签<sex>男<sex>
    private static void add() throws Exception {
        getParse();
        Element element=document.createElement("sex");
        Text text=document.createTextNode("男");
        element.appendChild(text);
        document.getElementsByTagName("student").item(0).appendChild(element);
        writeBack();
    }

    //删除上个方法新建的sex标签
    private static void delete() throws Exception{
        getParse();
        document.getElementsByTagName("student").item(0).removeChild(document.getElementsByTagName("sex").item(0));
        writeBack();
    }

    //将第二个学生的姓名改为王五
    private static void modify() throws Exception {
        getParse();
        document.getElementsByTagName("name").item(1).setTextContent("王五");
        writeBack();
    }

    //查询第一个name标签的内容
    private static void select() throws Exception {
        getParse();
        System.out.println(document.getElementsByTagName("name").item(0).getTextContent());
    }

    //遍历出所有的标签
    private static void selectAll() throws Exception{
        getParse();
        backtrack(document);
    }
    //递归
    private static void backtrack(Node node) {
        if(node.getNodeType()==Node.ELEMENT_NODE)
        {
            System.out.println(node.getNodeName());
        }
        NodeList list=node.getChildNodes();
        for(int i=0;i<list.getLength();i++)
        {
            backtrack(list.item(i));
        }
    }

    //将document从内存写回文件
    private static void writeBack()throws Exception {
        TransformerFactory transformerFactory=TransformerFactory.newInstance();
        Transformer transformer= transformerFactory.newTransformer();
        transformer.transform(new DOMSource(document), new StreamResult("src/1.xml"));
    }

    //初始化
    private static void getParse() throws Exception {
        DocumentBuilderFactory documentBuilderFactory=DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder=documentBuilderFactory.newDocumentBuilder();
        document=documentBuilder.parse("src/1.xml");
    }
}