上一篇使用HtmlAgilityPack抓取壁纸数据成功将图片存入数据库，本篇继续来完成一个全网各大平台的热点新闻数据的抓取。
同样的，可以先预览一下我个人博客中的成品：https://meowv.com/hot ????????????，和抓取壁纸的套路一样，大同小异。
本次要抓取的源有18个，分别是博客园、V2EX、SegmentFault、掘金、微信热门、豆瓣精选、IT之家、36氪、百度贴吧、百度热搜、微博热搜、知乎热榜、知乎日报、网易新闻、GitHub、抖音热点、抖音视频、抖音正能量。
还是将数据存入数据库，按部就班先将实体类和自定义仓储创建好，实体取名HotNews。贴一下代码：
//HotNews.cs
using System;
using Volo.Abp.Domain.Entities;namespace Meowv.Blog.Domain.HotNews
{public class HotNews : Entity<Guid>{/// <summary>/// 标题/// </summary>public string Title { get; set; }/// <summary>/// 链接/// </summary>public string Url { get; set; }/// <summary>/// SourceId/// </summary>public int SourceId { get; set; }/// <summary>/// 创建时间/// </summary>public DateTime CreateTime { get; set; }}
}
剩下的大家自己完成，最终数据库生成一张空的数据表，meowv_hotnews 。
然后还是将我们各大平台放到一个枚举类HotNewsEnum.cs中。
//HotNewsEnum.cs
using System.ComponentModel;namespace Meowv.Blog.Domain.Shared.Enum
{public enum HotNewsEnum{[Description("博客园")]cnblogs = 1,[Description("V2EX")]v2ex = 2,[Description("SegmentFault")]segmentfault = 3,[Description("掘金")]juejin = 4,[Description("微信热门")]weixin = 5,[Description("豆瓣精选")]douban = 6,[Description("IT之家")]ithome = 7,[Description("36氪")]kr36 = 8,[Description("百度贴吧")]tieba = 9,[Description("百度热搜")]baidu = 10,[Description("微博热搜")]weibo = 11,[Description("知乎热榜")]zhihu = 12,[Description("知乎日报")]zhihudaily = 13,[Description("网易新闻")]news163 = 14,[Description("GitHub")]github = 15,[Description("抖音热点")]douyin_hot = 16,[Description("抖音视频")]douyin_video = 17,[Description("抖音正能量")]douyin_positive = 18}
}
和上一篇抓取壁纸一样，做一些准备工作。
在.Application.Contracts层添加HotNewsJobItem<T>，在.BackgroundJobs层添加HotNewsJob用来处理爬虫逻辑，用构造函数方式注入仓储IHotNewsRepository。
//HotNewsJobItem.cs
using Meowv.Blog.Domain.Shared.Enum;namespace Meowv.Blog.Application.Contracts.HotNews
{public class HotNewsJobItem<T>{/// <summary>/// <see cref="Result"/>/// </summary>public T Result { get; set; }/// <summary>/// 来源/// </summary>public HotNewsEnum Source { get; set; }}
}
//HotNewsJob.CS
using Meowv.Blog.Domain.HotNews.Repositories;
using System;
using System.Net.Http;
using System.Threading.Tasks;namespace Meowv.Blog.BackgroundJobs.Jobs.HotNews
{public class HotNewsJob : IBackgroundJob{private readonly IHttpClientFactory _httpClient;private readonly IHotNewsRepository _hotNewsRepository;public HotNewsJob(IHttpClientFactory httpClient,IHotNewsRepository hotNewsRepository){_httpClient = httpClient;_hotNewsRepository = hotNewsRepository;}public async Task ExecuteAsync(){throw new NotImplementedException();}}
}
接下来明确数据源地址，因为以上数据源有的返回是HTML，有的直接返回JSON数据。为了方便调用，我这里还注入了IHttpClientFactory。
整理好的待抓取数据源列表是这样的。
...
var hotnewsUrls = new List<HotNewsJobItem<string>>
{new HotNewsJobItem<string> { Result = "https://www.cnblogs.com", Source = HotNewsEnum.cnblogs },new HotNewsJobItem<string> { Result = "https://www.v2ex.com/?tab=hot", Source = HotNewsEnum.v2ex },new HotNewsJobItem<string> { Result = "https://segmentfault.com/hottest", Source = HotNewsEnum.segmentfault },new HotNewsJobItem<string> { Result = "https://web-api.juejin.im/query", Source = HotNewsEnum.juejin },new HotNewsJobItem<string> { Result = "https://weixin.sogou.com", Source = HotNewsEnum.weixin },new HotNewsJobItem<string> { Result = "https://www.douban.com/group/explore", Source = HotNewsEnum.douban },new HotNewsJobItem<string> { Result = "https://www.ithome.com", Source = HotNewsEnum.ithome },new HotNewsJobItem<string> { Result = "https://36kr.com/newsflashes", Source = HotNewsEnum.kr36 },new HotNewsJobItem<string> { Result = "http://tieba.baidu.com/hottopic/browse/topicList", Source = HotNewsEnum.tieba },new HotNewsJobItem<string> { Result = "http://top.baidu.com/buzz?b=341", Source = HotNewsEnum.baidu },new HotNewsJobItem<string> { Result = "https://s.weibo.com/top/summary/summary", Source = HotNewsEnum.weibo },new HotNewsJobItem<string> { Result = "https://www.zhihu.com/api/v3/feed/topstory/hot-lists/total?limit=50&desktop=true", Source = HotNewsEnum.zhihu },new HotNewsJobItem<string> { Result = "https://daily.zhihu.com", Source = HotNewsEnum.zhihudaily },new HotNewsJobItem<string> { Result = "http://news.163.com/special/0001386F/rank_whole.html", Source = HotNewsEnum.news163 },new HotNewsJobItem<string> { Result = "https://github.com/trending", Source = HotNewsEnum.github },new HotNewsJobItem<string> { Result = "https://www.iesdouyin.com/web/api/v2/hotsearch/billboard/word", Source = HotNewsEnum.douyin_hot },new HotNewsJobItem<string> { Result = "https://www.iesdouyin.com/web/api/v2/hotsearch/billboard/aweme", Source = HotNewsEnum.douyin_video },new HotNewsJobItem<string> { Result = "https://www.iesdouyin.com/web/api/v2/hotsearch/billboard/aweme/?type=positive", Source = HotNewsEnum.douyin_positive },
};
...
其中有几个比较特殊的，掘金、百度热搜、网易新闻。
掘金需要发送Post请求，返回的是JSON数据，并且需要指定特有的请求头和请求数据，所以使用IHttpClientFactory创建了HttpClient对象。
百度热搜、网易新闻两个老大哥玩套路，网页编码是GB2312的，所以要专门为其指定编码方式，不然取到的数据都是乱码。
...
var web = new HtmlWeb();
var list_task = new List<Task<HotNewsJobItem<object>>>();hotnewsUrls.ForEach(item =>
{var task = Task.Run(async () =>{var obj = new object();if (item.Source == HotNewsEnum.juejin){using var client = _httpClient.CreateClient();client.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.14 Safari/537.36 Edg/83.0.478.13");client.DefaultRequestHeaders.Add("X-Agent", "Juejin/Web");var data = "{\"extensions\":{\"query\":{ \"id\":\"21207e9ddb1de777adeaca7a2fb38030\"}},\"operationName\":\"\",\"query\":\"\",\"variables\":{ \"first\":20,\"after\":\"\",\"order\":\"THREE_DAYS_HOTTEST\"}}";var buffer = data.SerializeUtf8();var byteContent = new ByteArrayContent(buffer);byteContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");var httpResponse = await client.PostAsync(item.Result, byteContent);obj = await httpResponse.Content.ReadAsStringAsync();}else{Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);obj = await web.LoadFromWebAsync(item.Result, (item.Source == HotNewsEnum.baidu || item.Source == HotNewsEnum.news163) ? Encoding.GetEncoding("GB2312") : Encoding.UTF8);}return new HotNewsJobItem<object>{Result = obj,Source = item.Source};});list_task.Add(task);
});
Task.WaitAll(list_task.ToArray());
循环 hotnewsUrls ，可以看到HotNewsJobItem我们返回的是object类型，因为有JSON又有HtmlDocument对象。所以这里为了能够统一接收，就是用了object。
针对掘金做了单独处理，使用HttpClient发送Post请求，返回JSON字符串数据。
针对百度热搜和网易新闻，使用Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);注册编码提供程序，然后在web.LoadFromWebAsync(...)加载网页数据的时候指定网页编码，我使用了一个三元表达式来处理。
完成上面这一步，就可以循环 list_task，使用XPath语法，或者解析JSON数据，去拿到数据了。
...
var hotNews = new List<HotNews>();
foreach (var list in list_task)
{var item = await list;var sourceId = (int)item.Source;...if (hotNews.Any()){await _hotNewsRepository.DeleteAsync(x => true);await _hotNewsRepository.BulkInsertAsync(hotNews);}
}
这个爬虫同样很简单，只要拿到标题和链接即可，所以主要目标是寻找到页面上的a标签列表。这个我觉得也没必要一个个去分析了，直接上代码。
// 博客园if (item.Source == HotNewsEnum.cnblogs){var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='post_item_body']/h3/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});}
// V2EX
if (item.Source == HotNewsEnum.v2ex)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//span[@class='item_title']/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = $"https://www.v2ex.com{x.GetAttributeValue("href", "")}",SourceId = sourceId,CreateTime = DateTime.Now});});
}
// SegmentFaultif (item.Source == HotNewsEnum.segmentfault){var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='news__item-info clearfix']/a").Where(x => x.InnerText.IsNotNullOrEmpty()).ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.SelectSingleNode(".//h4").InnerText,Url = $"https://segmentfault.com{x.GetAttributeValue("href", "")}",SourceId = sourceId,CreateTime = DateTime.Now});});}
// 掘金
if (item.Source == HotNewsEnum.juejin)
{var obj = JObject.Parse((string)item.Result);var nodes = obj["data"]["articleFeed"]["items"]["edges"];foreach (var node in nodes){hotNews.Add(new HotNews{Title = node["node"]["title"].ToString(),Url = node["node"]["originalUrl"].ToString(),SourceId = sourceId,CreateTime = DateTime.Now});}
}
// 微信热门
if (item.Source == HotNewsEnum.weixin)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//ul[@class='news-list']/li/div[@class='txt-box']/h3/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 豆瓣精选
if (item.Source == HotNewsEnum.douban)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='channel-item']/div[@class='bd']/h3/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});
}
// IT之家
if (item.Source == HotNewsEnum.ithome)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='lst lst-2 hot-list']/div[1]/ul/li/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 36氪
if (item.Source == HotNewsEnum.kr36)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='hotlist-main']/div[@class='hotlist-item-toptwo']/a[2]|//div[@class='hotlist-main']/div[@class='hotlist-item-other clearfloat']/div[@class='hotlist-item-other-info']/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = $"https://36kr.com{x.GetAttributeValue("href", "")}",SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 百度贴吧
if (item.Source == HotNewsEnum.tieba)
{var obj = JObject.Parse(((HtmlDocument)item.Result).ParsedText);var nodes = obj["data"]["bang_topic"]["topic_list"];foreach (var node in nodes){hotNews.Add(new HotNews{Title = node["topic_name"].ToString(),Url = node["topic_url"].ToString().Replace("amp;", ""),SourceId = sourceId,CreateTime = DateTime.Now});}
}
// 百度热搜
if (item.Source == HotNewsEnum.baidu)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//table[@class='list-table']//tr/td[@class='keyword']/a[@class='list-title']").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 微博热搜
if (item.Source == HotNewsEnum.weibo)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//table/tbody/tr/td[2]/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = $"https://s.weibo.com{x.GetAttributeValue("href", "").Replace("#", "%23")}",SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 知乎热榜
if (item.Source == HotNewsEnum.zhihu)
{var obj = JObject.Parse(((HtmlDocument)item.Result).ParsedText);var nodes = obj["data"];foreach (var node in nodes){hotNews.Add(new HotNews{Title = node["target"]["title"].ToString(),Url = $"https://www.zhihu.com/question/{node["target"]["id"]}",SourceId = sourceId,CreateTime = DateTime.Now});}
}
// 知乎日报
if (item.Source == HotNewsEnum.zhihudaily)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='box']/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = $"https://daily.zhihu.com{x.GetAttributeValue("href", "")}",SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 网易新闻
if (item.Source == HotNewsEnum.news163)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//div[@class='area-half left']/div[@class='tabBox']/div[@class='tabContents active']/table//tr/td[1]/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText,Url = x.GetAttributeValue("href", ""),SourceId = sourceId,CreateTime = DateTime.Now});});
}
// GitHub
if (item.Source == HotNewsEnum.github)
{var nodes = ((HtmlDocument)item.Result).DocumentNode.SelectNodes("//article[@class='Box-row']/h1/a").ToList();nodes.ForEach(x =>{hotNews.Add(new HotNews{Title = x.InnerText.Trim().Replace("\n", "").Replace(" ", ""),Url = $"https://github.com{x.GetAttributeValue("href", "")}",SourceId = sourceId,CreateTime = DateTime.Now});});
}
// 抖音热点
if (item.Source == HotNewsEnum.douyin_hot)
{var obj = JObject.Parse(((HtmlDocument)item.Result).ParsedText);var nodes = obj["word_list"];foreach (var node in nodes){hotNews.Add(new HotNews{Title = node["word"].ToString(),Url = $"#{node["hot_value"]}",SourceId = sourceId,CreateTime = DateTime.Now});}
}
// 抖音视频 & 抖音正能量
if (item.Source == HotNewsEnum.douyin_video || item.Source == HotNewsEnum.douyin_positive)
{var obj = JObject.Parse(((HtmlDocument)item.Result).ParsedText);var nodes = obj["aweme_list"];foreach (var node in nodes){hotNews.Add(new HotNews{Title = node["aweme_info"]["desc"].ToString(),Url = node["aweme_info"]["share_url"].ToString(),SourceId = sourceId,CreateTime = DateTime.Now});}
}
将item.Result转换成指定类型，最终拿到数据后，我们先删除所有数据后再批量插入。
然后新建扩展方法UseHotNewsJob()，在模块类中调用。
//MeowvBlogBackgroundJobsExtensions.cs
.../// <summary>/// 每日热点数据抓取/// </summary>/// <param name="context"></param>public static void UseHotNewsJob(this IServiceProvider service){var job = service.GetService<HotNewsJob>();RecurringJob.AddOrUpdate("每日热点数据抓取", () => job.ExecuteAsync(), CronType.Hour(1, 2));}
...
指定定时任务为每2小时运行一次。
...public override void OnApplicationInitialization(ApplicationInitializationContext context){...var service = context.ServiceProvider;...service.UseHotNewsJob();}
编译运行，此时周期性作业就会出现我们的定时任务了。
默认时间没到是不会执行的，我们手动执行等待一会看看效果。
执行完成后，成功将所有热点数据保存在数据库中，说明我们的爬虫已经搞定了，并且Hangfire会按照给定的规则去循环执行，你学会了吗？????????????
开源地址：https://github.com/Meowv/Blog/tree/blog_tutorial
![[JavaWeb-MySQL]数据库的基本概念和特点](https://img-blog.csdnimg.cn/20210717184414510.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzUxOTU1NDcw,size_16,color_FFFFFF,t_70)
![[Java基础]JDK内置注解](https://img-blog.csdnimg.cn/20210717200817382.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzUxOTU1NDcw,size_16,color_FFFFFF,t_70)
![[JavaWeb-MySQL]MySQL服务启动和关闭](https://img-blog.csdnimg.cn/20210717202929627.png)
![[Java基础]自定义注解之属性定义](https://img-blog.csdnimg.cn/20210718003909152.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzUxOTU1NDcw,size_16,color_FFFFFF,t_70)
![[JavaWeb-MySQL]MySQL登陆和退出](https://img-blog.csdnimg.cn/20210717204118729.png)
![[Java基础]自定义注解 格式本质](https://img-blog.csdnimg.cn/20210717214237172.png)
![[JavaWeb-MySQL]SQL基本概念，通用语法，分类](https://img-blog.csdnimg.cn/2021071721480965.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzUxOTU1NDcw,size_16,color_FFFFFF,t_70)
![[JavaWeb-MySQL]多表关系介绍](https://img-blog.csdnimg.cn/20210718192050982.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzUxOTU1NDcw,size_16,color_FFFFFF,t_70)