Java中使用Jsoup实现网页内容爬取与Html内容解析并使用EasyExcel实现导出为Excel文件

场景

Pythont通过request以及BeautifulSoup爬取几千条情话：

Pythont通过request以及BeautifulSoup爬取几千条情话_爬取情话-CSDN博客

Node-RED中使用html节点爬取HTML网页资料之爬取Node-RED的最新版本：

Node-RED中使用html节点爬取HTML网页资料之爬取Node-RED的最新版本_node-red html-CSDN博客

Jsoup

Jsoup是一种Java 的HTML(html也是XML文档)解析器，可直接解析某个URL地址、HTML文本内容。

它提供了一套易于操作的API，可通过DOM，CSS以及类似于jQuery选择器的操作方法来取出和操作数据。

使用jsoup就可以解析HTML。

Jsoup使用的是DOM解析方式，把整个HTML文档（XML文档）加载到内存中形成一棵DOM树，得到文档的Document对象。

HTML里的标签，会转换成Element对象。

官网地址：

jsoup: Java HTML parser, built for HTML editing, cleaning, scraping, and XSS safety

EasyExcel

Java解析、生成Excel比较有名的框架有Apache poi、jxl。但他们都存在一个严重的问题就是非常的耗内存，

poi有一套SAX模式的API可以一定程度的解决一些内存溢出的问题，但POI还是有一些缺陷，

比如07版Excel解压缩以及解压后存储都是在内存中完成的，内存消耗依然很大。

easyexcel重写了poi对07版Excel的解析，一个3M的excel用POI sax解析依然需要100M左右内存，

改用easyexcel可以降低到几M，并且再大的excel也不会出现内存溢出；03版依赖POI的sax模式，

在上层做了模型转换的封装，让使用者更加简单方便。

官网地址：

关于Easyexcel | Easy Excel

注：

博客：
https://blog.csdn.net/badao_liumang_qizhi 

实现

1、引入依赖

        <!--Jsoup 是一个用于解析HTML和XML文档的Java库-->
        <dependency>
            <groupId>org.jsoup</groupId>
            <artifactId>jsoup</artifactId>
            <version>1.11.3</version>
        </dependency>
 
        <!--EasyExcel是一个基于Java的、快速、简洁、解决大文件内存溢出的Excel处理工具-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>easyexcel</artifactId>
            <version>3.0.5</version>
        </dependency>

2、找到需要爬取的网页内容

比如以下面为例

2023财富世界500强企业榜单 2023全球500强企业 世界500强排名一览表→买购网

这里要获取500强排名数据，因为单次刷新网页只能返回100条数据，所以只解析前100条。获取更多数据可根据其分页请求规则分别进行爬取。

打开F12找到要爬取的数据的dom结构

这里要获取到id为t_container的div元素大的第22个子元素(索引为21)的table元素的tr元素的td数据。

3、编写测试代码，连接并解析html元素

        String url = "https://www.maigoo.com/news/3jcNODk3.html";
        try {
            //读取url，得到Document
            Document document = Jsoup.connect(url)
                    .ignoreContentType(true)
                    .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3")
                    .timeout(30000)
                    .header("referer","https://www.maigoo.com")
                    .get();
            Elements select = document.select("#t_container > div:eq(21) table tr");
        } catch (IOException e) {
            e.printStackTrace();
        }

注意这里使用选择器的语法：

#t_container 代表id为t_container

>代表找父元素下的子元素

div:eq(21) 代表第22个元素

table tr 代表table 标签下tr标签

更多select选择器用法

Use CSS selectors to find elements: jsoup Java HTML parser

Selector overview

• tagname: find elements by tag, e.g. div
• #id: find elements by ID, e.g. #logo
• .class: find elements by class name, e.g. .masthead
• [attribute]: elements with attribute, e.g. [href]
• [^attrPrefix]: elements with an attribute name prefix, e.g. [^data-] finds elements with HTML5 dataset attributes
• [attr=value]: elements with attribute value, e.g. [width=500] (also quotable, like [data-name='launch sequence'])
• [attr^=value], [attr$=value], [attr*=value]: elements with attributes that start with, end with, or contain the value, e.g. [href*=/path/]
• [attr~=regex]: elements with attribute values that match the regular expression; e.g. img[src~=(?i)\.(png|jpe?g)]
• *: all elements, e.g. *
• ns|tag: find elements by tag in a namespace prefix, e.g. fb|name finds  elements
• *|tag: final elements by tag in any namespace prefix, e.g. *|name finds  and  elements

Selector combinations

• el#id: elements with ID, e.g. div#logo
• el.class: elements with class, e.g. div.masthead
• el[attr]: elements with attribute, e.g. a[href]
• Any combination, e.g. a[href].highlight
• ancestor child: child elements that descend from ancestor, e.g. .body p finds p elements anywhere under a block with class "body"
• parent > child: child elements that descend directly from parent, e.g. div.content > p finds p elements; and body > * finds the direct children of the body tag
• siblingA + siblingB: finds sibling B element immediately preceded by sibling A, e.g. div.head + div
• siblingA ~ siblingX: finds sibling X element preceded by sibling A, e.g. h1 ~ p
• el, el, el: group multiple selectors, find unique elements that match any of the selectors; e.g. div.masthead, div.logo

Pseudo selectors

• :has(selector): find elements that contain elements matching the selector; e.g. div:has(p)
• :is(selector): find elements that match any of the selectors in the selector list; e.g. :is(h1, h2, h3, h4, h5, h6) finds any heading element
• :not(selector): find elements that do not match the selector; e.g. div:not(.logo)
• :contains(text): find elements that contain the given text. The search is case-insensitive; e.g. p:contains(jsoup)
• :containsOwn(text): find elements that directly contain the given text
• :matches(regex): find elements whose text matches the specified regular expression; e.g. div:matches((?i)login)
• :matchesOwn(regex): find elements whose own text matches the specified regular expression
• :lt(n): find elements whose sibling index (i.e. its position in the DOM tree relative to its parent) is less than n; e.g. td:lt(3)
• :gt(n): find elements whose sibling index is greater than n; e.g. div p:gt(2)
• :eq(n): find elements whose sibling index is equal to n; e.g. form input:eq(1)
• Note that the above indexed pseudo-selectors are 0-based, that is, the first element is at index 0, the second at 1, etc

除使用select选择器之外还可使用XPath选择器用法

Use XPath selectors to find elements and nodes: jsoup Java HTML parser

4、解析dom数据并赋值到对象添加到list

新建实体对象，并添加excel注解

import com.alibaba.excel.annotation.ExcelProperty;
import lombok.Builder;
import lombok.Data;
 
import java.io.Serializable;
 
@Data
@Builder
public class WealthEntity implements Serializable {
 
    private static final long serialVersionUID = -1760099890427975758L;
 
    @ExcelProperty(value = "排名",index = 0)
    private Integer index;
 
    @ExcelProperty(value = "公司名称",index = 1)
    private String companyName;
 
    @ExcelProperty(value = "收入",index = 2)
    private String income;
 
    @ExcelProperty(value = "利润",index = 3)
    private String profit;
 
}

进行dom解析和添加到list

            Elements select = document.select("#t_container > div:eq(21) table tr");
            List<WealthEntity> list = new ArrayList<>();
            for (int i = 1; i < select.size(); i++) {
                Element tr = select.get(i);
                Elements tds = tr.select("td");
                Integer index = Integer.valueOf(tds.get(0).text());
                String companyName = tds.get(1).text();
                String income = tds.get(2).text();
                String profit = tds.get(3).text();
                WealthEntity wealthEntity = WealthEntity.builder()
                        .index(index)
                        .companyName(companyName)
                        .income(income)
                        .profit(profit)
                        .build();
                list.add(wealthEntity);
            }

5、导出为excel

            String fileName = "D:/2023财富世界100强.xlsx";
            EasyExcel.write(fileName,WealthEntity.class).sheet("100强").doWrite(list);

6、完整示例代码

        String url = "https://www.maigoo.com/news/3jcNODk3.html";
        try {
            //读取url，得到Document
            Document document = Jsoup.connect(url)
                    .ignoreContentType(true)
                    .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3")
                    .timeout(30000)
                    .header("referer","https://www.maigoo.com")
                    .get();
            Elements select = document.select("#t_container > div:eq(21) table tr");
            List<WealthEntity> list = new ArrayList<>();
            for (int i = 1; i < select.size(); i++) {
                Element tr = select.get(i);
                Elements tds = tr.select("td");
                Integer index = Integer.valueOf(tds.get(0).text());
                String companyName = tds.get(1).text();
                String income = tds.get(2).text();
                String profit = tds.get(3).text();
                WealthEntity wealthEntity = WealthEntity.builder()
                        .index(index)
                        .companyName(companyName)
                        .income(income)
                        .profit(profit)
                        .build();
                list.add(wealthEntity);
            }
            String fileName = "D:/2023财富世界100强.xlsx";
            EasyExcel.write(fileName,WealthEntity.class).sheet("100强").doWrite(list);
        } catch (IOException e) {
            e.printStackTrace();
        }

7、运行结果