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
 */
@Component
public 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: