昨天搭建新框架的時候,遇到一個很奇怪的「Bug」,每次請求都會觸發兩次Aciton,舉例子吧,Demo:html
<!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <link rel="icon" type="image/x-icon" href="#" /> <title>@ViewData["Title"] - WebApplicationDemo</title> <meta name="keywords" content=""> <meta name="description" content=""> <meta name="author" content="Lio.Huang"> </head> <body> <div style="background-color:#808080;height:200px;"> @RenderBody() </div> </body> </html>
using System.Diagnostics; using System.Linq; using System.Threading.Tasks; using Microsoft.AspNetCore.Mvc; namespace WebApplicationDemo.Controllers { public class HomeController : Controller { public IActionResult Index() { return View(); } } }
<h1>Hi, I'm index page.</h1>
最簡單不過的代碼,而後啓動項目,無心中就發現了,過程當中發生了兩次請求:瀏覽器
再新增一個控制器測試仍然是如此。框架
試想第二次請求發生了什麼?加入一個請求統計的接口,攔截第二次請求。開擼:測試
public interface IRequestStat { int RequestNum { get; } /// <summary> /// 是否跳轉 /// </summary> /// <returns></returns> bool Redirect(); /// <summary> /// 請求次數累計 /// </summary> void Add(); } public class RequestStat : IRequestStat { public int RequestNum { get; private set; } public RequestStat() { RequestNum = 1; } public void Add() { RequestNum++; } public bool Redirect() { return RequestNum == 2; } }
public class HomeController : Controller { private readonly IRequestStat request; public HomeController(IRequestStat request) { this.request = request; } public IActionResult Index() { if (request.Redirect()) { return Redirect("https://www.baidu.com/"); } request.Add(); return View(); } }
當第二次請求時候,重定向到百度網。this
而後在Startup中註冊爲單例:spa
public void ConfigureServices(IServiceCollection services) { services.AddMvc(); services.AddSingleton<IRequestStat, RequestStat>(); }
啓動!3d
發現它並無跳轉到百度網,可是也發現了"Bug"所在,favicon.ico是來自百度的。日誌
第二次請求,其實瀏覽器是請求favicon.ico的tab圖標文件。code
若是頁面沒有提供favicon.ico時會從請求裏嘗試獲取,但在生產過程當中,Action是帶有業務邏輯,咱們確定是不但願莫名其妙的被觸發一次。htm
在_Layout.cshtml中把favicon.ico加上便可
<!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <link rel="icon" type="image/x-icon" href="/favicon.ico" /> <title>@ViewData["Title"] - WebApplicationDemo</title> <meta name="keywords" content=""> <meta name="description" content=""> <meta name="author" content="Lio.Huang"> </head> <body> <div style="background-color:#808080;height:200px;"> @RenderBody() </div> </body> </html>
真是一不當心就掉坑了,記錄一下爬坑日誌,一步一個 腳印 坑。