Java爬虫框架之WebMagic实战

一、介绍

WebMagic是一个简单灵活的Java爬虫框架。基于WebMagic，你可以快速开发出一个高效、易维护的爬虫。

二、如何学习

1.查看官网

官网地址为:http://webmagic.io/官网详细文档:http://webmagic.io/docs/zh/

2.跑通hello world示例(具体可以参考官网，也可以参考博客)

我下面写的单元测试案例，可作为Hello World示例。

注意需要导入Maven依赖:

<dependency> <groupId>us.codecraft</groupId> <artifactId>webmagic-core</artifactId> <version>0.7.3</version></dependency><dependency> <groupId>us.codecraft</groupId> <artifactId>webmagic-extension</artifactId> <version>0.7.3</version></dependency>

3.带着一个目的

说说我的目的，最近我开发的博客系统，其中有个导入第三方博客的插件，这个插件比较简单就是一个搜索框，在对应的搜索框里面填写URL，点击搜索即可导入到自己的博客。

以导入博客园单篇文章为例:

下面是我的源代码(单篇文章导入,我已经将其封装成一个工具类):

import cn.hutool.core.date.DateUtil;import com.blog.springboot.dto.CnBlogModelDTO;import com.blog.springboot.entity.Posts;import com.blog.springboot.service.PostsService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import us.codecraft.webmagic.Page;import us.codecraft.webmagic.Site;import us.codecraft.webmagic.Spider;import us.codecraft.webmagic.pipeline.ConsolePipeline;import us.codecraft.webmagic.processor.PageProcessor;import us.codecraft.webmagic.selector.Selectable;import javax.annotation.PostConstruct;/** * 导入博客园文章工具类 */@Componentpublic class WebMagicCnBlogUtils implements PageProcessor { @Autowired private PostsService postService; public static WebMagicCnBlogUtils magicCnBlogUtils; @PostConstruct public void init() { magicCnBlogUtils = this; magicCnBlogUtils.postService = this.postService; } private Site site = Site.me() .setDomain('https://www.cnblogs.com/') .setSleepTime(1000) .setUserAgent('Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'); @Override public void process(Page page) { Selectable obj = page.getHtml().xpath('//div[@class=’post’]'); Selectable title = obj.xpath('//h1[@class=’postTitle’]//a'); Selectable content = obj.xpath('//div[@class=’blogpost-body’]'); System.out.println('title:' + title.replace('<[^>]*>', '')); System.out.println('content:' + content); CnBlogModelDTO blog = new CnBlogModelDTO(); blog.setTitle(title.toString()); blog.setContent(content.toString()); Posts post = new Posts(); String date = DateUtil.date().toString(); post.setPostAuthor(1L); post.setPostTitle(title.replace('<[^>]*>', '').toString()); post.setPostContent(content.toString()); post.setPostExcerpt(content.replace('<[^>]*>', '').toString()); post.setPostDate(date); post.setPostDate(date); post.setPostModified(date); boolean importPost = magicCnBlogUtils.postService.insert(post); if (importPost) { System.out.println('success'); } else { System.out.println('fail'); } } @Override public Site getSite() { return site; } /** * 导入单篇博客园文章数据 * * @param url */ public static void importSinglePost(String url) { Spider.create(new WebMagicCnBlogUtils()).addUrl(url).addPipeline(new ConsolePipeline()).run(); }}

单元测试代码:

import com.blog.springboot.dto.CnBlogModelDTO;import us.codecraft.webmagic.Page;import us.codecraft.webmagic.Site;import us.codecraft.webmagic.Spider;import us.codecraft.webmagic.pipeline.ConsolePipeline;import us.codecraft.webmagic.processor.PageProcessor;import us.codecraft.webmagic.selector.Selectable;public class WebMagicJunitTest implements PageProcessor { private Site site = Site.me() .setDomain('https://www.cnblogs.com/') .setSleepTime(1000) .setUserAgent('Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'); @Override public void process(Page page) { Selectable obj = page.getHtml().xpath('//div[@class=’post’]'); Selectable title = obj.xpath('//h1[@class=’postTitle’]//a'); Selectable content = obj.xpath('//div[@class=’blogpost-body’]'); System.out.println('title:' + title.replace('<[^>]*>', '')); System.out.println('content:' + content); } @Override public Site getSite() { return site; } public static void importSinglePost(String url) { Spider.create(new WebMagicJunitTest()).addUrl(url).addPipeline(new ConsolePipeline()).run(); } public static void main(String[] args) { WebMagicJunitTest.importSinglePost('https://www.cnblogs.com/youcong/p/9404007.html'); }

另外我是怎么知道要爬取哪些数据呢?需求第一，然后通过Chrome或Firefox浏览器检查元素，如图:

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