ASP.NET Core 7.0中AddRewrite为何触发HTTP 301重定向？

我在ASP.NET Core中添加了Rewrite规则，但却出现了重定向现象。原本以为AddRewrite的核心作用是对HTTP客户端保持透明。

完整代码 #

using System.Collections.Generic;
using System.IO;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Configuration;
using MyProject.Preview.Configuration;
using Microsoft.AspNetCore.Rewrite;

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseHttpLogging();

var options = new RewriteOptions().AddRewrite(@"^p/([a-zA-Z0-9]*)/w/([a-zA-Z0-9-]*)","/preview/$1/workspace/$2/wwwroot",skipRemainingRules: true);

app.UseRewriter(options);

app.UseDefaultFiles(new DefaultFilesOptions
{
   FileProvider = new PhysicalFileProvider(Path.Combine(builder.Configuration.GetSection("Pad").GetValue<string>(nameof(PadConfiguration.StorageRootPath)), "artifacts")),
   RequestPath = "/preview",
   DefaultFileNames = new List<string> { "index.html" }
});

app.UseStaticFiles(new StaticFileOptions
{
   FileProvider = new PhysicalFileProvider(
   Path.Combine(builder.Configuration.GetSection("Pad").GetValue<string>(nameof(PadConfiguration.StorageRootPath)), "artifacts")),
   RequestPath = "/preview",
   ServeUnknownFileTypes = true,
});

app.Run();

CURL输出 #

curl -I http://localhost:5033/p/d8f7i885d/w/583bdffe-09bd-4a03-8b4e-5006f743c617
HTTP/1.1 301 Moved Permanently
Date: Wed, 26 Jul 2023 04:52:22 GMT
Server: Kestrel
Location: http://localhost:5033/preview/d8f7i885d/workspace/583bdffe-09bd-4a03-8b4e-5006f743c617/wwwroot/

问题：为何RewriteOptions会触发重定向？ #

原因分析 #

重定向并非由Rewrite中间件触发，而是UseDefaultFiles中间件的默认行为导致：

• 你的Rewrite规则将请求路径重写为/preview/xxx/workspace/xxx/wwwroot，这个路径对应服务器上的一个目录（wwwroot是文件夹）。
• UseDefaultFiles中间件在处理目录请求时，如果请求路径没有以/结尾，会自动发送301重定向到带/的路径，之后再返回目录下的默认文件（比如index.html）。

解决办法 #

方案一：修改Rewrite规则，让目标路径以/结尾

修改重写规则的目标路径，添加末尾斜杠，这样请求直接匹配带斜杠的目录路径，避免触发重定向：

var options = new RewriteOptions().AddRewrite(@"^p/([a-zA-Z0-9]*)/w/([a-zA-Z0-9-]*)","/preview/$1/workspace/$2/wwwroot/",skipRemainingRules: true);

方案二：禁用UseDefaultFiles的自动重定向行为

通过设置RedirectToAppendTrailingSlash为false，关闭中间件的重定向逻辑：

app.UseDefaultFiles(new DefaultFilesOptions
{
   FileProvider = new PhysicalFileProvider(Path.Combine(builder.Configuration.GetSection("Pad").GetValue<string>(nameof(PadConfiguration.StorageRootPath)), "artifacts")),
   RequestPath = "/preview",
   DefaultFileNames = new List<string> { "index.html" },
   RedirectToAppendTrailingSlash = false // 禁用自动添加斜杠的重定向
});

内容的提问来源于stack exchange，提问作者Brad