【java爬虫】利用webmagic框架实战demo

webmagic框架:http://webmagic.io/

WebMagic的结构分为Downloader、PageProcessor、Scheduler、Pipeline四大组件

PageProcessor主要分为三个部分，分别是爬虫的配置、页面元素的抽取和链接的发现。

Pipeline用于保存结果的组件，下面我们实现自定义Pipeline，可以实现保存结果到文件、数据库等一系列功能

很多功能自己进去慢慢研究哈，这里就不一一赘述了。

下面直接进入主题，爬我的博客首页的数据：https://www.cnblogs.com/loaderman/

查看首页的源码研究一下下：

第一步：maven配置webmagic 详见：http://webmagic.io/docs/zh/posts/ch2-install/with-maven.html

第二步：直接根据文档进行编码实战：

定义实体类

public class LoadermanModel {
    private String title;
    private String detailUrl;
    private String content;
    private String date;

    public LoadermanModel() {
    }

    public LoadermanModel(String title, String detailUrl, String content, String date) {
        this.title = title;
        this.detailUrl = detailUrl;
        this.content = content;
        this.date = date;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDetailUrl() {
        return detailUrl;
    }

    public void setDetailUrl(String detailUrl) {
        this.detailUrl = detailUrl;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

自定义PageProcessor

import us.codecraft.webmagic.Page;
import us.codecraft.webmagic.Site;
import us.codecraft.webmagic.processor.PageProcessor;
import us.codecraft.webmagic.selector.Html;

import java.util.ArrayList;
import java.util.List;

public class LoadermanPageProcessor implements PageProcessor {
    // 部分一：抓取网站的相关配置，包括编码、抓取间隔、重试次数等
    private Site site = Site.me().setRetryTimes(5).setUserAgent("User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0");

    @Override
    public void process(Page page) {
        List<String> pageItemList = page.getHtml().xpath("//div[@class='post']").all();
        ArrayList<LoadermanModel> list = new ArrayList<>();
        for (int i = 0; i < pageItemList.size(); i++) {
            Html html = Html.create(pageItemList.get(i));
            LoadermanModel loadermanModel=new LoadermanModel();
            loadermanModel.setTitle(html.xpath("//a[@class='postTitle2']/text()").toString() );
            loadermanModel.setDetailUrl(html.xpath("//a[@class='postTitle2']").links().toString());
            loadermanModel.setContent(html.xpath("//div[@class='c_b_p_desc']/text()").toString() );
            loadermanModel.setDate(html.xpath("//p[@class='postfoot']/text()").toString() );
            list.add(loadermanModel);
        }

        page.putField("data", list);


        if (page.getResultItems().get("data") == null) {
            //skip this page
            page.setSkip(true);
        }

    }

    @Override
    public Site getSite() {
        return site;
    }
}

自定义Pipeline,，对爬取后的数据提取和处理

import com.alibaba.fastjson.JSON;

import us.codecraft.webmagic.ResultItems;
import us.codecraft.webmagic.Task;
import us.codecraft.webmagic.pipeline.Pipeline;
import us.codecraft.webmagic.utils.FilePersistentBase;

import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;


public class LoadermanlPipeline extends FilePersistentBase implements Pipeline {
    public LoadermanlPipeline(String path) {
        this.setPath(path);
    }

    public void process(ResultItems resultItems, Task task) {
        String path = "LoadermanlPipelineGetData";

        try {
            PrintWriter printWriter = new PrintWriter(new FileWriter(this.getFile(path+ ".json")));
            printWriter.write(JSON.toJSONString(resultItems.get("data")));
            printWriter.close();
        } catch (IOException var5) {

        }
    }
}

开启爬虫：

    Spider.create(new LoadermanPageProcessor())
                .addUrl("https://www.cnblogs.com/loaderman/")
                //自定义Pipeline，保存json文件到本地
                .addPipeline(new LoadermanlPipeline("D:\\loaderman\\"))
                //开启5个线程抓取
                .thread(5)
                //启动爬虫
                .run();

效果如下：

搞定！