前言

今天我們來(lái)講講如何使用.NET開(kāi)源（MIT License）的輕量、靈活、高性能、跨平臺(tái)的分布式網(wǎng)絡(luò)爬蟲(chóng)框架DotnetSpider來(lái)快速實(shí)現(xiàn)網(wǎng)頁(yè)數(shù)據(jù)抓取功能。

注意：為了自身安全請(qǐng)?jiān)趪?guó)家法律允許范圍內(nèi)開(kāi)發(fā)網(wǎng)頁(yè)爬蟲(chóng)功能。

網(wǎng)頁(yè)數(shù)據(jù)抓取需求

本文我們以抓取博客園10天推薦排行榜第一頁(yè)的文章標(biāo)題、文章簡(jiǎn)介和文章地址為示例，并把抓取下來(lái)的數(shù)據(jù)保存到對(duì)應(yīng)的txt文本中。

請(qǐng)求地址：https://www.cnblogs.com/aggsite/topdiggs

創(chuàng)建控制臺(tái)應(yīng)用

創(chuàng)建名為DotnetSpiderExercise的控制臺(tái)應(yīng)用。

安裝DotnetSpider NuGet包

NuGet包管理器搜索：DotnetSpider

添加Serilog日志組件

NuGet包管理器搜索：Serilog.AspNetCore

添加RecommendedRankingModel

namespace DotnetSpiderExercise
{
    public class RecommendedRankingModel
    {
        /// <summary>
        /// 文章標(biāo)題
        /// </summary>
        public string ArticleTitle { get; set; }


        /// <summary>
        /// 文章簡(jiǎn)介
        /// </summary>
        public string ArticleSummary { get; set; }


        /// <summary>
        /// 文章地址
        /// </summary>
        public string ArticleUrl { get; set; }
    }
}

添加RecommendedRankingSpider

網(wǎng)頁(yè)數(shù)據(jù)抓取的業(yè)務(wù)邏輯都在這里面。

using DotnetSpider.DataFlow.Parser;
using DotnetSpider.DataFlow;
using DotnetSpider.Downloader;
using DotnetSpider.Http;
using DotnetSpider.Scheduler.Component;
using DotnetSpider.Selector;
using DotnetSpider;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Serilog;
using DotnetSpider.Scheduler;
using Microsoft.Extensions.Hosting;
using System.Reflection;


namespace DotnetSpiderExercise
{
    public class RecommendedRankingSpider : Spider
    {
        public RecommendedRankingSpider(IOptions<SpiderOptions> options,
            DependenceServices services,
            ILogger<Spider> logger) : base(options, services, logger)
        {
        }


        public static async Task RunAsync()
        {
            var builder = Builder.CreateDefaultBuilder<RecommendedRankingSpider>();
            builder.UseSerilog();
            builder.UseDownloader<HttpClientDownloader>();
            builder.UseQueueDistinctBfsScheduler<HashSetDuplicateRemover>();
            await builder.Build().RunAsync();
        }


        protected override async Task InitializeAsync(CancellationToken stoppingToken = default)
        {
            //添加自定義解析
            AddDataFlow(new Parser());
            //使用控制臺(tái)存儲(chǔ)器
            AddDataFlow(new ConsoleStorage());
            //添加采集請(qǐng)求:博客園10天推薦排行榜
            await AddRequestsAsync(new Request("https://www.cnblogs.com/aggsite/topdiggs")
            {
                //請(qǐng)求超時(shí)10秒
                Timeout = 10000
            });
        }


        class Parser : DataParser
        {
            public override Task InitializeAsync()
            {
                return Task.CompletedTask;
            }


            protected override Task ParseAsync(DataFlowContext context)
            {
                var recommendedRankingList = new List<RecommendedRankingModel>();
                // 網(wǎng)頁(yè)數(shù)據(jù)解析
                var number = 1;
                var recommendedList = context.Selectable.SelectList(Selectors.XPath(".//article[@class='post-item']"));
                foreach (var news in recommendedList)
                {
                    var articleTitle = news.Select(Selectors.XPath(".//a[@class='post-item-title']"))?.Value;
                    var articleSummary = news.Select(Selectors.XPath(".//p[@class='post-item-summary']"))?.Value?.Replace("\n", "").Replace(" ", "");
                    var articleUrl = news.Select(Selectors.XPath(".//a[@class='post-item-title']/@href"))?.Value;


                    Console.WriteLine($"第{number}篇文章 標(biāo)題：{articleTitle}");


                    recommendedRankingList.Add(new RecommendedRankingModel
                    {
                        ArticleTitle = articleTitle,
                        ArticleSummary = articleSummary,
                        ArticleUrl = articleUrl
                    });


                    number++;
                }


                using (StreamWriter sw = new StreamWriter("RecommendedRanking.txt"))
                {
                    foreach (RecommendedRankingModel model in recommendedRankingList)
                    {
                        string line = $"文章標(biāo)題：{model.ArticleTitle}\r\n文章簡(jiǎn)介：{model.ArticleSummary}\r\n文章地址：{model.ArticleUrl}";
                        sw.WriteLine(line + "\r\n ========================================================================================== \r\n");
                    }
                }
                return Task.CompletedTask;
            }
        }
    }
}

Program執(zhí)行數(shù)據(jù)抓取

namespace DotnetSpiderExercise
{
    public class Program
    {
        static async Task Main(string[] args)
        {
            Console.WriteLine("網(wǎng)頁(yè)數(shù)據(jù)抓取開(kāi)始...");


            await RecommendedRankingSpider.RunAsync();


            Console.WriteLine("網(wǎng)頁(yè)數(shù)據(jù)抓取完成...");
        }
    }
}