Java爬虫实现Jsoup利用dom方法遍历Document对象
先给出网页地址：
https://wall.alphacoders.com/featured.php?lang=Chinese
主要步骤：
利用Jsoup的connect方法获取Document对象
String html = "https://wall.alphacoders.com/featured.php?lang=Chinese";
Document doc = Jsoup.connect(html).get();
内容过长，就不再显示。
我们以这部分为例：
<ul class="nav nav-pills">
<li><a href="https://alphacoders.com/site/about-us" rel="external nofollow" rel="external nofollow" >About Us</a></li>
<li><a href="https://alphacoders.com/site/faq" rel="external nofollow" rel="external nofollow" >FAQ</a></li>
<li><a href="https://alphacoders.com/site/privacy" rel="external nofollow" rel="external nofollow" >Privacy Policy</a></li>
<li><a href="https://alphacoders.com/site/tos" rel="external nofollow" rel="external nofollow" >Terms Of Service</a></li>
<li><a href="https://alphacoders.com/site/acceptable_use" rel="external nofollow" rel="external nofollow" >Acceptable Use</a></li>
<li><a href="https://alphacoders.com/site/etiquette" rel="external nofollow" rel="external nofollow" >Etiquette</a></li>
<li><a href="https://alphacoders.com/site/advertising" rel="external nofollow" rel="external nofollow" >Advertise With Us</a></li>
<li><a id="change_consent">Change Consent</a></li>
</ul>
我们先找到所有的ul：
Elements elements = doc.getElementsByTag("ul");
输出如下：
<ul class="nav navbar-nav center">
<li> <a title="Submit Wallpapers" href="https://alphacoders.com/site/submit-wallpaper" rel="external nofollow" ><i class="el el-circle-arrow-up"></i> 提交</a> </li>
<li> <a href="https://alphacoders.com/contest" rel="external nofollow" ><i class="el el-gift"></i> 精美奖品</a> </li>
</ul>
<ul class="nav navbar-nav navbar-right center">
<li> <a href="language.php?lang=Chinese" rel="external nofollow" > <img src="http://huoche.7234.cn/images/jb51/jhmsyia0hgv.png" alt="Chinese-flag"> 中文 </a> </li>
<li> <a href="https://alphacoders.com/users/login" rel="external nofollow" ><i class="el el-user"></i> 登录</a> </li>
<li> <a href="https://alphacoders.com/users/register" rel="external nofollow" ><i class="el el-edit"></i> 注册</a> </li>
</ul>
<ul class="pagination">
<li class="active"><a id="prev_page" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >< 上一页</a></li>
<li class="active"><a>1</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >2</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=3" rel="external nofollow" rel="external nofollow" rel="external nofollow" >3</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=4" rel="external nofollow" rel="external nofollow" rel="external nofollow" >4</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=5" rel="external nofollow" rel="external nofollow" rel="external nofollow" >5</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=6" rel="external nofollow" rel="external nofollow" rel="external nofollow" >6</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=7" rel="external nofollow" rel="external nofollow" rel="external nofollow" >7</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=8" rel="external nofollow" >8</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=9" rel="external nofollow" >9</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=10" rel="external nofollow" >10</a></li>
<li><a>...</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=319" rel="external nofollow" rel="external nofollow" rel="external nofollow" >319</a></li>
<li><a id="next_page" href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >下一页 ></a></li>
</ul>
<ul class="pagination">
<li class="active"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >< 上一页</a></li>
<li class="active"><a>1</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >2</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=3" rel="external nofollow" rel="external nofollow" rel="external nofollow" >3</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=4" rel="external nofollow" rel="external nofollow" rel="external nofollow" >4</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=5" rel="external nofollow" rel="external nofollow" rel="external nofollow" >5</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=6" rel="external nofollow" rel="external nofollow" rel="external nofollow" >6</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=7" rel="external nofollow" rel="external nofollow" rel="external nofollow" >7</a></li>
<li><a>...</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=319" rel="external nofollow" rel="external nofollow" rel="external nofollow" >319</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >下一页 ></a></li>
</ul>
<ul class="pagination">
<li class="active"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><< </a></li>
<li class="active"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >< 上一页</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >下一页 ></a></li>
<li><a title="末页 (319)" href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=319" rel="external nofollow" rel="external nofollow" rel="external nofollow" > >></a></li>
</ul>
<ul class="pagination">
<li class="active"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >1</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=2" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >2</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=3" rel="external nofollow" rel="external nofollow" rel="external nofollow" >3</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=4" rel="external nofollow" rel="external nofollow" rel="external nofollow" >4</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=5" rel="external nofollow" rel="external nofollow" rel="external nofollow" >5</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=6" rel="external nofollow" rel="external nofollow" rel="external nofollow" >6</a></li>
<li><a href="https://wall.alphacoders.com/featured.php?lang=Chinese&page=7" rel="external nofollow" rel="external nofollow" rel="external nofollow" >7</a></li>
</ul>
<ul class="nav nav-pills">
<li><a href="https://alphacoders.com/site/about-us" rel="external nofollow" rel="external nofollow" >About Us</a></li>
<li><a href="https://alphacoders.com/site/faq" rel="external nofollow" rel="external nofollow" >FAQ</a></li>
<li><a href="https://alphacoders.com/site/privacy" rel="external nofollow" rel="external nofollow" >Privacy Policy</a></li>
<li><a href="https://alphacoders.com/site/tos" rel="external nofollow" rel="external nofollow" >Terms Of Service</a></li>
<li><a href="https://alphacoders.com/site/acceptable_use" rel="external nofollow" rel="external nofollow" >Acceptable Use</a></li>
<li><a href="https://alphacoders.com/site/etiquette" rel="external nofollow" rel="external nofollow" >Etiquette</a></li>
<li><a href="https://alphacoders.com/site/advertising" rel="external nofollow" rel="external nofollow" >Advertise With Us</a></li>
<li><a id="change_consent">Change Consent</a></li>
</ul>
可以发现class为"nav nav-pills"的只有一个，我们找到它：
Elements elements = doc.getElementsByTag("ul");
//System.out.println(elements);
Element tempElement = null;
for(Element element : elements) {
if (element.className().equals("nav nav-pills")) {
tempElement = element;
//System.out.println(element.className());
break;
}
}
循环遍历这个ul，输出其中每一个li里每一个a的href和rel属性：
Elements li = tempElement.getElementsByTag("li");
for(Element element : li) {
Elements element2 = element.getElementsByTag("a");
for(Element element3 : element2) {
String hrefString = element3.attr("href");
String relString = element3.attr("rel");
if(hrefString != "" && relString != "") {
System.out.println("href=" + hrefString + " rel="external nofollow" rel="external nofollow" " + "rel=" + relString);
}
}
}
最终结果：
href=https://alphacoders.com/site/about-us rel=nofollow
href=https://alphacoders.com/site/faq rel=nofollow
href=https://alphacoders.com/site/privacy rel=nofollow
href=https://alphacoders.com/site/tos rel=nofollow
href=https://alphacoders.com/site/acceptable_use rel=nofollow
href=https://alphacoders.com/site/etiquette rel=nofollow
href=https://alphacoders.com/site/advertising rel=nofollow
完整代码：
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import java.io.IOException;
import org.jsoup.Jsoup;
/**
* @ClassName: Jsoup_Test
* @description:
* @author: KI
* @Date: 2020年8月17日 下午8:15:14
*/
public class Jsoup_Test {
public static void main(String[] args) throws IOException {
// TODO 自动生成的方法存根
String html = "https://wall.alphacoders.com/featured.php?lang=Chinese";
Document doc = Jsoup.connect(html).get();
System.out.println(doc);
Elements elements = doc.getElementsByTag("ul");
//System.out.println(elements);
Element tempElement = null;
for(Element element : elements) {
if (element.className().equals("nav nav-pills")) {
tempElement = element;
//System.out.println(element.className());
break;
}
}
System.out.println(tempElement);
Elements li = tempElement.getElementsByTag("li");
for(Element element : li) {
Elements element2 = element.getElementsByTag("a");
for(Element element3 : element2) {
String hrefString = element3.attr("href");
String relString = element3.attr("rel");
if(hrefString != "" && relString != "") {
System.out.println("href=" + hrefString + " rel="external nofollow" rel="external nofollow" " + "rel=" + relString);
}
}
}
}
}
到此这篇关于Java爬虫实现Jsoup利用dom方法遍历Document对象的文章就介绍到这了,更多相关Java Jsoup遍历Document对象内容请搜索软件开发网以前的文章或继续浏览下面的相关文章希望大家以后多多支持软件开发网！
