[开源 .NET 跨平台 Crawler 数据采集 爬虫框架: DotnetSpider] [三] 配置式爬虫

[DotnetSpider 系列目录]

• 一、初衷与架构设计
• 二、基本使用
• 三、配置式爬虫
• 四、JSON数据解析与配置系统
• 五、如何做全站采集

上一篇介绍的基本的使用方式，自由度很高，但是编写的代码相对就多了。而我所在的行业其实大部分都是定题爬虫, 只需要采集指定的页面并结构化数据。为了提高开发效率, 我实现了利用实体配置的方式来实现爬虫

创建 Console 项目

利用NUGET添加包

DotnetSpider2.Extension

定义配置式数据对象

• 数据对象必须继承 SpiderEntity
• EntityTableAttribute中可以定义数据名称、表名及表名后缀、索引、主键或者需要更新的字段
• EntitySelector 定义从页面数据中抽取数据对象的规则
• TargetUrlsSelector定义符合规则(正则)的目标链接, 用于加入到队列中

定义一个原始的数据对象类

public class Product : SpiderEntity
{
}

使用Chrome打开京东商品页 http://list.jd.com/list.html?cat=9987,653,655&page=2&JL=6_0_0&ms=5#J_main

1. 使用快捷键F12打开开发者工具
2. 选中一个商品，并观察Html结构

可以看到每个商品都在class为gl-i-wrap j-sku-item的DIV下面，因此添加EntitySelector到数据对象Product的类名上面。（ XPath的写法不是唯一的，不熟悉的可以去W3CSCHOLL学习一下, 框架也支持使用Css甚至正则来选择出正确的Html片段）。

　　　

        [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
        public class Product : SpiderEntity
        {
        }

1. 添加数据库及索引信息

           [EntityTable("test", "sku", EntityTable.Monday, Indexs = new[] { "Category" }, Uniques = new[] { "Category,Sku", "Sku" })]
           [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
           public class Product : SpiderEntity
           {
           }

2. 假设你需要采集SKU信息，观察HTML结构，计算出相对的XPath, 为什么是相对XPath？因为EntitySelector已经把HTML截成片段了，内部的Html元素查询都是相对于EntitySelector查询出来的元素。最后再加上数据库中列的信息

           [EntityTable("test", "sku", EntityTable.Monday, Indexs = new[] { "Category" }, Uniques = new[] { "Category,Sku", "Sku" })]
           [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
           public class Product : SpiderEntity
           {
               [PropertyDefine(Expression = "./@data-sku")]
               public string Sku { get; set; }
           }

3. 爬虫内部，链接是通过Request对象来存储信息的，构造Request对象时可以添加额外的属性值，这时候允许数据对象从Request的额外属性值中查询数据

           [EntityTable("test", "sku", EntityTable.Monday, Indexs = new[] { "Category" }, Uniques = new[] { "Category,Sku", "Sku" })]
           [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
           public class Product : SpiderEntity
           {
               [PropertyDefine(Expression = "./@data-sku")]
               public string Sku { get; set; }
   
               [PropertyDefine(Expression = "name", Type = SelectorType.Enviroment)]
               public string Category { get; set; }
           }

配置爬虫（继承EntitySpider）

    public class JdSkuSampleSpider : EntitySpider
    {
        public JdSkuSampleSpider() : base("JdSkuSample", new Site
        {
            //HttpProxyPool = new HttpProxyPool(new KuaidailiProxySupplier("快代理API"))
        })
        {
        }

        protected override void MyInit(params string[] arguments)
        {
            Identity = Identity ?? "JD SKU SAMPLE";

            ThreadNum = ;
            // dowload html by http client
            Downloader = new HttpClientDownloader();

            // storage data to mysql, default is mysql entity pipeline, so you can comment this line. Don't miss sslmode.
            AddPipeline(new MySqlEntityPipeline("Database='mysql';Data Source=localhost;User ID=root;Password=;Port=3306;SslMode=None;"));
            AddStartUrl("http://list.jd.com/list.html?cat=9987,653,655&page=2&JL=6_0_0&ms=5#J_main", new Dictionary<string, object> { { "name", "手机" }, { "cat3", "" } });
            AddEntityType<Product>();
        }
    }

1. 其中AddStartUrl第二个参数Dictionary<string, object>就是用于Enviroment查询的数据

2. TargetUrlsSelector，可以配置数据链接的合法性验证，以及目标URL的获取。如下表示目标URL的获取区域是由XPATH选择，并且要符合正则表达式 &page=[0-9]+&

           [EntityTable("test", "jd_sku", EntityTable.Monday, Indexs = new[] { "Category" }, Uniques = new[] { "Category,Sku", "Sku" })]
           [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
           [TargetUrlsSelector(XPaths = new[] { "//span[@class=\"p-num\"]" }, Patterns = new[] { @"&page=[0-9]+&" })]
           public class Product : SpiderEntity
           {
               [PropertyDefine(Expression = "./@data-sku")]
               public string Sku { get; set; }
   
               [PropertyDefine(Expression = "name", Type = SelectorType.Enviroment)]
               public string Category { get; set; }
           }

1. 添加一个MySql的数据管道，只需要配置好连接字符串即可

   context.AddPipeline(new MySqlEntityPipeline("Database='test';Data Source=localhost;User ID=root;Password=1qazZAQ!;Port=3306"));

完整代码

    public class JdSkuSampleSpider : EntitySpider
    {
        public JdSkuSampleSpider() : base("JdSkuSample", new Site
        {
            //HttpProxyPool = new HttpProxyPool(new KuaidailiProxySupplier("快代理API"))
        })
        {
        }

        protected override void MyInit(params string[] arguments)
        {
            Identity = Identity ?? "JD SKU SAMPLE";

            ThreadNum = ;
            // dowload html by http client
            Downloader = new HttpClientDownloader();

            // storage data to mysql, default is mysql entity pipeline, so you can comment this line. Don't miss sslmode.
            AddPipeline(new MySqlEntityPipeline("Database='mysql';Data Source=localhost;User ID=root;Password=;Port=3306;SslMode=None;"));
            AddStartUrl("http://list.jd.com/list.html?cat=9987,653,655&page=2&JL=6_0_0&ms=5#J_main", new Dictionary<string, object> { { "name", "手机" }, { "cat3", "" } });
            AddEntityType<Product>();
        }
    }

    [EntityTable("test", "jd_sku", EntityTable.Monday, Indexs = new[] { "Category" }, Uniques = new[] { "Category,Sku", "Sku" })]
    [EntitySelector(Expression = "//li[@class='gl-item']/div[contains(@class,'j-sku-item')]")]
    [TargetUrlsSelector(XPaths = new[] { "//span[@class=\"p-num\"]" }, Patterns = new[] { @"&page=[0-9]+&" })]
    public class Product : SpiderEntity
    {
        [PropertyDefine(Expression = "./@data-sku", Length = )]
        public string Sku { get; set; }

        [PropertyDefine(Expression = "name", Type = SelectorType.Enviroment, Length = )]
        public string Category { get; set; }

        [PropertyDefine(Expression = "cat3", Type = SelectorType.Enviroment)]
        public int CategoryId { get; set; }

        [PropertyDefine(Expression = "./div[1]/a/@href")]
        public string Url { get; set; }

        [PropertyDefine(Expression = "./div[5]/strong/a")]
        public long CommentsCount { get; set; }

        [PropertyDefine(Expression = ".//div[@class='p-shop']/@data-shop_name", Length = )]
        public string ShopName { get; set; }

        [PropertyDefine(Expression = ".//div[@class='p-name']/a/em", Length = )]
        public string Name { get; set; }

        [PropertyDefine(Expression = "./@venderid", Length = )]
        public string VenderId { get; set; }

        [PropertyDefine(Expression = "./@jdzy_shop_id", Length = )]
        public string JdzyShopId { get; set; }

        [PropertyDefine(Expression = "Monday", Type = SelectorType.Enviroment)]
        public DateTime RunId { get; set; }
    }

运行爬虫

public class Program
{
    public static void Main(string[] args)
    {
        JdSkuSampleSpider spider = new JdSkuSampleSpider();
        spider.Run();
    }
}

不到57行代码完成一个爬虫，是不是异常的简单？

代码地址

https://github.com/zlzforever/DotnetSpider 望各位大佬加星 

参与开发或有疑问

博文写得比较早, 框架修改有时会来不及更新博文中的代码, 请查看DotnetSpider.Sample项目中的样例爬虫

QQ群: 477731655

邮箱: zlzforever@163.com