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xml+html 概述

news 来源：原创 2025/8/16 11:40:52

1.什么是xml

xml 是可扩展标记语言的缩写： Extensible Markup Language。

<root><h1> text 1</h1>
</root>
web 应用开发，需要配置 web.xml，就是个典型的 xml文件
<web-app><servlet><servlet-name>HelloServlet</servlet-name><servlet-class>HelloServlet</servlet-class></servlet><servlet-mapping><servlet-name>HelloServlet</servlet-name><url-pattern>/hello</url-pattern></servlet-mapping></web-app>
dao或者mapper层映射文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.xml.test.mapper.helloMapper"></mapper>
上述的 root、h1、 web-app、servlet-name....mapper 整体称为元素

简单举例： <h1> text 1</h1> 格式为 :<元素名称> 元素内容 </元素名称>

h1就是元素名称， text 1 是元素内容。整体就是一个元素。

2.什么是html

html 是 HyperText Markup Language的缩写,超文本标记语言。

<html><body><p>Hello HTML</p></body>
</html>
是不是发现类似 xml？

        html 可以简单看成是 xml 的一个子集。

         html 用的都是一些预先定义的元素，如 <html>, <a>, <body>, <table> 。

         xml 什么元素都可以自定义：如 <a> , <b>, <aabb> 。

3.XML 和 HTML 的区别：

目的：
- XML：用于存储和传输数据，强调数据的结构化。
- HTML：用于创建和显示网页内容，强调如何展示数据。
自定义标签：
- XML：可以自定义标签。
- HTML：使用预定义的标签。
语法要求：
- XML：要求严格的语法，每个开始标签必须有对应的结束标签，并且标签大小写敏感。
- HTML：语法相对宽松，标签大小写不敏感，部分标签可以没有结束标签（例如 <li>）。
使用场景：
- XML：主要用于数据交换，如 Web 服务中的数据传输，配置文件，文档存储等。
- HTML：用于创建网站页面，显示内容给用户。为啥叫超文本标记语言？因为超越一般文本，其他文本记录数据，而html 记录数据同时，还能呈现出文字颜色，位置，大小等。

4.解析 xml

解析的几种方式：

1. java 本身自带对 xml 的解析。在 javax.xml 这个包下，非常难用，难用到想吐。这种方式叫做 sax/dom
2. 因为 java 自带的很难用，所以就出现了更方便的第三方工具 dom4j, 解析效率大大提高了。 XML从入门到深入（超详细）-CSDN博客推荐文章
3. 现在又出现了更方便的 jsoup, 我们就会讲解如何用 jsoup 来解析 xml。

前面讲过html 看作xml子集，解析方式一样的。

要求解析：<html><body><p>Hello HTML</p></body></html>

任何开发，除了jdk，jvm自带的包，都要先下载jar包

如：jsoup-1.11.2.jar

package com.test.xml.analysis.example;import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;public class Test {public static void main(String[] args) throws Exception {String html = "<html><body><p>Hello HTML</p></body></html>";
//1. 把文本解析成 Document 对象， Document 对象就代表整个 xml 文档。Document doc = Jsoup.parse(html);//2. 获取所有的 p 元素Elements as= doc.getElementsByTag("p");for (Element e : as) {
//3.打印出p元素中的元素内容System.out.println(e.text());}}
}

5.获取文档针对4的拆分

5.1获取文档

获取Document对象的方式有多种，常见的就是基于 字符串，文件，网页地址。

package com.test.xml.analysis.example;import java.io.File;
import java.net.URL;import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;public class Test {public static void main(String[] args) throws Exception {String html1 = "<html><body><p>Hello HTML</p></body></html>";Document doc = Jsoup.parse(html1);System.out.println("基于字符串方式得到的 Document:\r\n"+ doc);File f = new File("a.html");if(f.exists()) {Document fileDoc = Jsoup.parse(f,"utf-8");System.out.println("基于文件方式得到的 Document:\r\n"+ fileDoc);}String url = "http://www.baidu.com";Document urlDoc= Jsoup.parse(new URL(url),5000); //超过5秒就报错System.out.println("基于URL方式得到的 Document:\r\n"+ urlDoc);}
}

5.2 获取元素

获取元素比较常见的几种方式： 通过id, 标签或者类名称获取。

假设有文件 b.html 里面内容为：

<div class="header-container"><div class="bookwrapper  clearfix">      <div id="brandProdName"><div id="logocover"></div><div id="productName" >Documentation</div></div><br class="clearfloat" /></div></div><a href="https://blog.csdn.net/weixin_48306950/article/details/121639656">循环依赖解决</a> 
<a href="https://www.baidu.com/">百度网址 </a> <form id="searchForm" onsubmit="return search()"><input type="hidden" name="category" value="java"/><input type="hidden" name="product" value="e25407-01"/><input type="hidden" name="q" value="" id="keywordreal"/><label for="searchField"><input type="text" id="searchField" value="Search the online Java Tutorials"size="30" onclick="this.value='';" /></label><input type="submit" value="Submit" />
</form>

java对应获取元素代码

public static void main(String[] args) throws Exception {File f = new File("b.html");if(!f.exists())return;Document doc = Jsoup.parse(f,"utf-8");//通过id获取     <div id="productName" >Documentation</div>Element e = doc.getElementById("productName");System.out.println(e);//通过标签获取  <a href="h....Elements es;es = doc.getElementsByTag("a");show(es);//通过类名称获取  <div class="header-container">es = doc.getElementsByClass("header-container");show(es);//通过属性获取     <input type="hidden" name="category" value="java"/>es = doc.getElementsByAttribute("name");show(es);}private static void show(Elements es) {for (Element e : es) {System.out.println(e);}}

5.3获取文本和内容

区分文本内容 <a><b>123</b></a>

内容是指节点的所有数据，包括子元素。元素a之间为内容
文本是指元素内的纯文本数据，不包括任何标签。元素b之间为内容

c.html 如下

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title>
</head>
<body>
<div id="d1" class="class1test  class2" ><p>Hello, world!</p>
</div></body>
</html>

public static void main(String[] args)  {  /*  File f = new File("c.html");if (!f.exists()) return;*/// 通过类加载器获取资源文件输入流InputStream ins = ResourceLoader.class.getClassLoader().getResourceAsStream("c.html");Document doc = Jsoup.parse(ins, "utf-8", "");Element e = doc.getElementById("d1");//获取属性System.out.println(e.attr("id")); //d1//获取所有属性System.out.println(e.attributes()); //  id="d1" class="class1test  class2"//获取idSystem.out.println(e.id()); //d1//获取类名称System.out.println(e.className());//  class1test  class2//获取所有类名称System.out.println(e.classNames());// [class1test, class2]//获取文本System.out.println(e.text());   //  Hello, world!//获取html/内容System.out.println(e.html());   //    <p>Hello, world!</p>//获取外html  本质就是该元素本身System.out.println(e.outerHtml());  
/*        <div id="d1" class="class1test  class2"> <p>Hello, world!</p> </div>
*///获取标签信息System.out.println(e.tagName());  // div }

注意：在 Maven 项目中，如果 c.html 文件放在 src/main/resources 目录下，那么该文件会被打包到 target/classes 目录里，作为类路径资源进行访问。你不能直接使用 new File("c.html") 来访问这个文件这样在当前工作目录中查找该文件，而不是在类路径中。

回忆下之前概念。对比上述 div标签中添加的内容带 p 标签，而不仅是只有文本 Hello

5.4 选择器

选择器语法

在选择元素的时候，除了使用方法名如 getElementById 这样的外，还可以用选择器语法来选择。操作起来就像 jquery，比如getElementById 就可以写成是 select("#id")。

package com.test.xml.example;import java.io.File;import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;public class Test {static Document doc;public static void main(String[] args) throws Exception {// 通过类加载器获取资源文件输入流InputStream ins = ResourceLoader.class.getClassLoader().getResourceAsStream("b.html");doc = Jsoup.parse(ins,"utf-8","");//像 jquery 那样的选择器语法show("选择所有的超链", "a");show("根据id进行选择", "#logocover");show("根据class进行选择", ".clearfloat");show("根据属性进行选择", "[href]");show("有属性以tar开头", "[^tar]");show("根据属性值选择", "[type='application/javascript']");show("属性值以什么开头", "[href^='http://www.oracle.com']");show("属性值以什么结尾", "[href$='index.html']");show("属性值包含什么", "[href*='download']");}private static void show(String text, String selector) {show(text,selector,3);}private static void show(String text, String selector, int limit) {Elements es =doc.select(selector);if(es.size()>1)System.out.println(String.format("%s - 使用的选择器是: \"%s\" \t (最多显示 %d 条 )", text,selector,limit)); elseSystem.out.println(String.format("%s - 使用的选择器是: \"%s\"", text,selector)); int i =0;for (Element e : es) {if(i++<limit)System.out.println(e);}System.out.println();}}

b.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en-US" xmlns="http://www.w3.org/1999/xhtml" xml:lang=
"en-US">
<head>
<title>The Java™ Tutorials</title>
<meta name="Description" content=
"Tutorials and reference guides for the Java Programming Language" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<style type="text/css">
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<li><a href="collections/index.html">Collections</a> —
Lessons on using and extending the Java Collections Framework.</li>
<li><a href="datetime/index.html">Date-Time APIs</a> — How to
use the <tt>java.time</tt> pages to write date and time code.</li>
<li><a href="deployment/index.html">Deployment</a> — How to
package applications and applets using JAR files, and deploy them
using Java Web Start and Java Plug-in.</li>
<li><a href="extra/certification/index.html">Preparation for Java
Programming Language Certification</a> — List of available
training and tutorial resources.</li>
</ul>
<h2>Creating Graphical User Interfaces</h2>
<ul class="BlueArrows">
<li><a href="uiswing/index.html">Creating a GUI with Swing</a>
— A comprehensive introduction to GUI creation on the Java
platform.</li>
<li><a href="https://docs.oracle.com/javafx/index.html">Creating a
JavaFX GUI</a> — A collection of JavaFX tutorials.</li>
</ul>
<h2>Specialized Trails and Lessons</h2>
<p>These trails and lessons are only available as web pages.</p>
<ul class="BlueArrows">
<li><a href="networking/index.html">Custom Networking</a> —
An introduction to the Java platform's powerful networking
features.</li>
<li><a href="ext/index.html">The Extension Mechanism</a> —
How to make custom APIs available to all applications running on
the Java platform.</li>
<li><a href="extra/fullscreen/index.html">Full-Screen Exclusive
Mode API</a> — How to write applications that more fully
utilize the user's graphics hardware.</li>
<li><a href="extra/generics/index.html">Generics</a> — An
enhancement to the type system that supports operations on objects
of various types while providing compile-time type safety. Note
that this lesson is for advanced users. The <a href=
"java/index.html">Java Language</a> trail contains a <a href=
"java/generics/index.html">Generics</a> lesson that is suitable for
beginners.</li>
<li><a href="i18n/index.html">Internationalization</a> — An
introduction to designing software so that it can be easily adapted
(localized) to various languages and regions.</li>
<li><a href="javabeans/index.html">JavaBeans</a> — The Java
platform's component technology.</li>
<li><a href="jdbc/index.html">JDBC Database Access</a> —
Introduces an API for connectivity between the Java applications
and a wide range of databases and data sources.</li>
<li><a href="jmx/index.html">JMX</a>— Java Management
Extensions provides a standard way of managing resources such as
applications, devices, and services.</li>
<li><a href="jndi/index.html">JNDI</a>— Java Naming and
Directory Interface enables accessing the Naming and Directory
Service such as DNS and LDAP.</li>
<li><a href="jaxp/index.html">JAXP</a> — Introduces the Java
API for XML Processing (JAXP) technology.</li>
<li><a href="jaxb/index.html">JAXB</a> — Introduces the Java
architecture for XML Binding (JAXB) technology.</li>
<li><a href="rmi/index.html">RMI</a> — The Remote Method
Invocation API allows an object to invoke methods of an object
running on another Java Virtual Machine.</li>
<li><a href="reflect/index.html">Reflection</a> — An API that
represents ("reflects") the classes, interfaces, and objects in the
current Java Virtual Machine.</li>
<li><a href="security/index.html">Security</a> — Java
platform features that help protect applications from malicious
software.</li>
<li><a href="sound/index.html">Sound</a> — An API for playing
sound data from applications.</li>
<li><a href="2d/index.html">2D Graphics</a> — How to display
and print 2D graphics in applications.</li>
<li><a href="sdp/index.html">Sockets Direct Protocol</a> —
How to enable the Sockets Direct Protocol to take advantage of
InfiniBand.</li>
</ul>
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5.5 操作属性和内容

5.5之前都是读取，那么问题来了-能修改吗？可以啊，不然网页上标签等变颜色，图片咋来的

jsoup 除了可以解析 html/xml 外，还可以进行修改行为。

如图示例，给 P元素增加class (类属性)，并修改内容

   public static void main(String[] args) throws Exception {/*  File f = new File("c.html"); 直接读取if (!f.exists()) return;*/// 通过类加载器获取资源文件输入流   因为maven项目 放在 resources目录下，用加载器获取InputStream ins = ResourceLoader.class.getClassLoader().getResourceAsStream("d.html");Document doc = Jsoup.parse(ins, "utf-8", "");System.out.println(doc);Element e = doc.select("p").first();e.attr("class", "class1");e.appendText(" Hello JSoup");//原文本追加 文字/文本System.out.println();System.out.println(doc);}