[开源 .NET 跨平台 Crawler 数据采集 爬虫框架: DotnetSpider] [四] JSON数据解析

[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

场景模拟

接上一篇, 假设由于漏存JD SKU对应的店铺信息。这时我们需要重新完全采集所有的SKU数据吗？补爬的话历史数据就用不了了。因此，去京东页面上找看是否有提供相关的接口。

查找API请求接口

安装 Fiddler, 并打开

在谷歌浏览器中访问： http://list.jd.com/list.html?cat=1315,1343,9719

在Fiddler查找一条条的访问记录，找到我们想要的接口

　　　　

编写爬虫

分析返回的数据结果，我们可以先写出数据对象的定义（观察Expression的值已经是JsonPath查询表达式了，同时Type必须设置为Type = SelectorType.JsonPath）。另外需要注意的是，这次的爬虫是更新型爬虫，就是说采集到的数据补充回原表，那么就一定要设置主键是什么，即在数据类上添加主键的定义

[Schema("jd", "sku_v2", TableSuffix.Monday)]
[EntitySelector(Expression = "$.[*]", Type = SelectorType.JsonPath)]
[Indexes(Primary = "sku")]
public class ProductUpdater : ISpiderEntity
{
[StoredAs("sku", DataType.String, 25)]
[PropertySelector(Expression = "$.pid", Type = SelectorType.JsonPath)]
public string Sku { get; set; }

[StoredAs("shopname", DataType.String, 100)]
[PropertySelector(Expression = "$.seller", Type = SelectorType.JsonPath)]
public string ShopName { get; set; }

[StoredAs("shopid", DataType.String, 25)]
[PropertySelector(Expression = "$.shopId", Type = SelectorType.JsonPath)]
public string ShopId { get; set; }
}

定义Pipeline的类型为Update

context.AddEntityPipeline(new MySqlEntityPipeline
{
ConnectString = "Database='taobao';Data Source= ;User ID=root;Password=1qazZAQ!;Port=4306",
Mode = PipelineMode.Update
});

由于返回的数据中还有一个json()这样的pagging，所以需要先做一个截取操作，框架提供了PageHandler接口，并且我们实现了大量常用的Handler，用于HTML的解析前的一些处理操作，因此完整的代码如下

    public class JdShopDetailSpider : EntitySpiderBuilder
{
protected override EntitySpider GetEntitySpider()
{
var context = new EntitySpider(new Site())
{
TaskGroup = "JD SKU Weekly",
Identity = "JD Shop details " + DateTimeUtils.MondayRunId,
CachedSize = 1,
ThreadNum = 8,
Downloader = new HttpClientDownloader
{
DownloadCompleteHandlers = new IDownloadCompleteHandler[]
{
new SubContentHandler
{
Start = "json(",
End = ");",
StartOffset = 5,
EndOffset = 0
}
}
},
PrepareStartUrls = new PrepareStartUrls[]
{
new BaseDbPrepareStartUrls()
{
Source = DataSource.MySql,
ConnectString = "Database='test';Data Source= localhost;User ID=root;Password=1qazZAQ!;Port=3306",
QueryString = $"SELECT * FROM jd.sku_v2_{DateTimeUtils.MondayRunId} WHERE shopname is null or shopid is null order by sku",
Columns = new [] {new DataColumn { Name = "sku"} },
FormateStrings = new List<string> { "http://chat1.jd.com/api/checkChat?my=list&pidList={0}&callback=json" }
}
}
};
context.AddEntityPipeline(new MySqlEntityPipeline
{
ConnectString = "Database='taobao';Data Source=localhost ;User ID=root;Password=1qazZAQ!;Port=4306",
Mode = PipelineMode.Update
});
context.AddEntityType(typeof(ProductUpdater), new TargetUrlExtractor
{
Region = new Selector { Type = SelectorType.XPath, Expression = "//*[@id=\"J_bottomPage\"]" },
Patterns = new List<string> { @"&page=[0-9]+&" }
});
return context;
}

[Schema("jd", "sku_v2", TableSuffix.Monday)]
[EntitySelector(Expression = "$.[*]", Type = SelectorType.JsonPath)]
[Indexes(Primary = "sku")]
public class ProductUpdater : ISpiderEntity
{
[StoredAs("sku", DataType.String, 25)]
[PropertySelector(Expression = "$.pid", Type = SelectorType.JsonPath)]
public string Sku { get; set; }

[StoredAs("shopname", DataType.String, 100)]
[PropertySelector(Expression = "$.seller", Type = SelectorType.JsonPath)]
public string ShopName { get; set; }

[StoredAs("shopid", DataType.String, 25)]
[PropertySelector(Expression = "$.shopId", Type = SelectorType.JsonPath)]
public string ShopId { get; set; }
}
}