黑马程序员__dom4j解析XML文档

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dom4j的特点：必须一层一层获取。

package cn.itcast.sax;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.DefaultHandler;

public class Demo3 {

public static void main(String[] args) throws IOException, SAXException, ParserConfigurationException {

// 获得解析工厂

SAXParserFactory factory = SAXParserFactory.newInstance();

// 得到解析器

SAXParser sp = factory.newSAXParser();

// 得到读取器

XMLReader reader = sp.getXMLReader();

// 设置内容处理器(implements Contenthandler或extends DefaultHandler)

reader.setContentHandler(new BeanListHandler());

// 读取XML文档内容

reader.parse("src/book.xml");

// 把XML文档中的每一本书封装到一个book对象，并把多个book对象放在一个list集合返回

}

}

class BeanListHandler extends DefaultHandler {

private List list = new ArrayList();

private String currentTag;

private Book book;

@Override

public void startElement(String uri, String localName, String name,

Attributes attributes) throws SAXException {

// TODO Auto-generated method stub

currentTag = name;

if ("书".equals(currentTag)) {

book = new Book();

}

}

@Override

public void characters(char[] ch, int start, int length)

throws SAXException {

if ("书名".equals(currentTag)) {

String name = new String(ch, start, length);

book.setName(name);

}

if ("作者".equals(currentTag)) {

String author = new String(ch, start, length);

book.setAuthor(author);

}

if ("售价".equals(currentTag)) {

String price = new String(ch, start, length);

book.setAuthor(price);

}

}

@Override

public void endElement(String uri, String localName, String qName)

throws SAXException {

if ("书".equals("name")) {

list.add(book);

book = null;

}

currentTag = null;

}

public List getList(){

return list;

}

}

publicclass Demo1 {

/* @Test

public void readAttr() throws DocumentException{

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/book.xml"));

Element root=document.getRootElement();

Element book=(Element)root.element("书").get(1);

String value=book.element("书名").attribute("name").getValue();

System.out.println(value);

}*/

@Test

publicvoid add() throws DocumentException, IOException{

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/book.xml"));

Element book=document.getRootElement().element("书");

book.addElement("售价").setText("209元");

OutputFormat format=OutputFormat.createPrettyPrint();

format.setEncoding("UTF-8");

XMLWriter writer=new XMLWriter(new FileOutputStream("src/book.xml"),format);

writer.write(document);

writer.close();

}

}

//在第一本书指定位置添加一个新的售价：<售价>209元</售价>--更改保存了所有孩子的list集合的顺序

@Test

publicvoid add2() throws DocumentException, IOException{

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/book.xml"));

Element book=document.getRootElement().element("书");

List list=book.elements();

Element price=DocumentHelper.createElement("售价");

price.setText("309元");

list.add(2,price);

OutputFormat format=OutputFormat.createPrettyPrint();

format.setEncoding("UTF-8");

XMLWriter writer=new XMLWriter(new FileOutputStream("src/book.xml"),format);

writer.write(document);

writer.close();

}

//删除指定节点

@Test

publicvoid delete() throws DocumentException, IOException{

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/book.xml"));

Element price=document.getRootElement().element("书").element("售价");

price.getParent().remove(price);

OutputFormat format=OutputFormat.createPrettyPrint();

format.setEncoding("UTF-8");

XMLWriter writer= new XMLWriter(new FileOutputStream("src/book.xml"),format);

writer.write(document);

writer.close();

}

//更新信息

publicvoid update() throws Exception{

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/book.xml"));

Element book=(Element) document.getRootElement().elements("书").get(1);

book.element("作者").setText("黎活明");

OutputFormat format=OutputFormat.createPrettyPrint();

format.setEncoding("UTF-8");

XMLWriter writer= new XMLWriter(new FileOutputStream("src/book.xml"),format);

writer.write(document);

writer.close();

}

XPath

用XPath模拟登陆

publicclass Demo5 {

publicstaticvoid main(String[] args) throws Exception{

String username="aaa";

String password="123";

//检测XML文档是否有匹配的用户名和密码

SAXReader reader=new SAXReader();

Document document=reader.read(new File("src/users.xml"));

Node node=document.selectSingleNode("//user[@username='"+username+"' and @password='"+password+"']");

if(node==null){

System.out.println("您输入的用户名或密码有误");

}

else{

System.out.println("登陆成功");

}

}

}

XML Schema

XML Schema文件自身就是一个XML文件，扩展名为.xsd

一个XML Schema文档通常称之为模式文档（约束文档），遵循这个文档书写的XML文件称之为实例文档！

在XML Schema中，每个约束模式文档都可以被赋以一个唯一的名称空间，名称空间用一个唯一的URI（Uniform Resource Identifier，统一资源标识符）表示。

Schema 语法：

定义简单元素：<xs:element name=”XXXX” type=”yyy”/>

XXX:元素的名称，yyy:元素的数据类型

最常用的类型：

xs:string /xs:decimal/xs:integer/xs:boolean/xs:date/xs:time

一道打印M的面试题（平面图形题--通用解题方案：利用二维数组）

publicclass MTest {

publicstaticvoid main(String[] args){

int x=2;

int y=0;

boolean flag=true;

int arr[][]=newint[3][9];

for(int i=1;i<=9;i++){

arr[x][y]=i;

y++;

if(flag==false){

x--;

}

if(flag==true){

x++;

}

if(x<0){

flag=true;

x+=2;

}

if(x>2){

flag=false;

x-=2;

}

}

for(int i=0;i<arr.length;i++){

for(int j=0;j<arr[i].length;j++){

if(arr[i][j]==0){

System.out.print(" ");

}else{

System.out.print(arr[i][j]);

}

}

System.out.println();

}

}

}

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