Java爬蟲實現(xiàn)Jsoup利用dom方法遍歷Document對象

更新時間：2022年05月17日 16:49:51 作者：Cyril_KI

本文主要介紹了Java爬蟲實現(xiàn)Jsoup利用dom方法遍歷Document對象，文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價值，需要的朋友們下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

先給出網(wǎng)頁地址：

https://wall.alphacoders.com/featured.php?lang=Chinese

主要步驟：

利用Jsoup的connect方法獲取Document對象

String html = "https://wall.alphacoders.com/featured.php?lang=Chinese";
Document doc = Jsoup.connect(html).get();

內(nèi)容過長，就不再顯示。

我們以這部分為例：

<ul class="nav nav-pills"> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >About Us</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >FAQ</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >Privacy Policy</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >Terms Of Service</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >Acceptable Use</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >Etiquette</a></li> 
    <li><a  rel="external nofollow"  rel="external nofollow"  >Advertise With Us</a></li> 
    <li><a id="change_consent">Change Consent</a></li> 
</ul>

我們先找到所有的ul：

Elements elements = doc.getElementsByTag("ul");

輸出如下：

<ul class="nav navbar-nav center"> 
 <li> <a title="Submit Wallpapers"  rel="external nofollow" ><i class="el el-circle-arrow-up"></i> 提交</a> </li> 
 <li> <a  rel="external nofollow" ><i class="el el-gift"></i> 精美獎品</a> </li> 
</ul>
<ul class="nav navbar-nav navbar-right center"> 
 <li> <a href="language.php?lang=Chinese" rel="external nofollow" > <img src="https://static.alphacoders.com/wa/Chinese-flag.png" alt="Chinese-flag">   中文    </a> </li> 
 <li> <a   rel="external nofollow" ><i class="el el-user"></i> 登錄</a> </li> 
 <li> <a  rel="external nofollow" ><i class="el el-edit"></i> 注冊</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" >&lt; 上一頁</a></li> 
 <li class="active"><a>1</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >2</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >3</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >4</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >5</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >6</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >7</a></li> 
 <li><a  rel="external nofollow" >8</a></li> 
 <li><a  rel="external nofollow" >9</a></li> 
 <li><a  rel="external nofollow" >10</a></li> 
 <li><a>...</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >319</a></li> 
 <li><a id="next_page"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >下一頁 &gt;</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" >&lt; 上一頁</a></li> 
 <li class="active"><a>1</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >2</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >3</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >4</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >5</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >6</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >7</a></li> 
 <li><a>...</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >319</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >下一頁 &gt;</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" >&lt;&lt; </a></li> 
 <li class="active"><a href="#" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >&lt; 上一頁</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >下一頁 &gt;</a></li> 
 <li><a title="末頁 (319)"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" > &gt;&gt;</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  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >2</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >3</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >4</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >5</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >6</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" >7</a></li> 
</ul>
<ul class="nav nav-pills"> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >About Us</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >FAQ</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >Privacy Policy</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >Terms Of Service</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >Acceptable Use</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >Etiquette</a></li> 
 <li><a  rel="external nofollow"  rel="external nofollow"  >Advertise With Us</a></li> 
 <li><a id="change_consent">Change Consent</a></li> 
</ul>

可以發(fā)現(xiàn)class為"nav nav-pills"的只有一個，我們找到它：

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;
    }
}

循環(huán)遍歷這個ul，輸出其中每一個li里每一個a的href和rel屬性：

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);
        }
    }
}

最終結(jié)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

完整代碼：

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 自動生成的方法存根
?? ??? ?
?? ??? ?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);
?? ??? ??? ??? ?}
?? ??? ??? ?}
?? ??? ?}?? ??? ?

?? ?}

}

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