ASP.NET Core 中间件

ASP.NET Core 中间件原理

什么是中间件

用IApplicationBuilder创建一个中间件管道

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;

public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.Run(async context =>
{
await context.Response.WriteAsync("Hello, World!");
});
}
}

next

public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.Use(async (context, next) =>
{
// Do work that doesn't write to the Response.
await next.Invoke();
// Do logging or other work that doesn't write to the Response.
});

app.Run(async context =>
{
await context.Response.WriteAsync("Hello from 2nd delegate.");
});
}
}

下一个委托（next）。在应答（response）已经开始后改变

HttpResponse

排序

Configure

public void Configure(IApplicationBuilder app)
{
app.UseExceptionHandler("/Home/Error"); // Call first to catch exceptions
// thrown in the following middleware.

app.UseStaticFiles();                   // Return static files and end pipeline.

app.UseAuthentication();               // Authenticate before you access
// secure resources.

app.UseMvcWithDefaultRoute();          // Add MVC to the request pipeline.
}

public void Configure(IApplicationBuilder app)
{
app.UseStaticFiles();         // Static files not compressed
// by middleware.
app.UseResponseCompression();
app.UseMvcWithDefaultRoute();
}

Use, Run, and Map

Use

Run

和Map

Use

Run

Map*

public class Startup
{
private static void HandleMapTest1(IApplicationBuilder app)
{
app.Run(async context =>
{
await context.Response.WriteAsync("Map Test 1");
});
}

private static void HandleMapTest2(IApplicationBuilder app)
{
app.Run(async context =>
{
await context.Response.WriteAsync("Map Test 2");
});
}

public void Configure(IApplicationBuilder app)
{
app.Map("/map1", HandleMapTest1);

app.Map("/map2", HandleMapTest2);

app.Run(async context =>
{
await context.Response.WriteAsync("Hello from non-Map delegate. <p>");
});
}
}

http://localhost:1234

Map

HttpRequest.Path

HttpRequest.PathBase

Func<HttpContext, bool>

下面的示例用于检测query字符串变量
branch
的存在：

public class Startup
{
private static void HandleBranch(IApplicationBuilder app)
{
app.Run(async context =>
{
var branchVer = context.Request.Query["branch"];
await context.Response.WriteAsync($"Branch used = {branchVer}");
});
}

public void Configure(IApplicationBuilder app)
{
app.MapWhen(context => context.Request.Query.ContainsKey("branch"),
HandleBranch);

app.Run(async context =>
{
await context.Response.WriteAsync("Hello from non-Map delegate. <p>");
});
}
}

http://localhost:1234

Map

app.Map("/level1", level1App => {
level1App.Map("/level2a", level2AApp => {
// "/level1/level2a"
//...
});
level1App.Map("/level2b", level2BApp => {
// "/level1/level2b"
//...
});
});

app.Map("/level1/level2", HandleMultiSeg);

内置中间件

编写中间件

public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.Use((context, next) =>
{
var cultureQuery = context.Request.Query["culture"];
if (!string.IsNullOrWhiteSpace(cultureQuery))
{
var culture = new CultureInfo(cultureQuery);

CultureInfo.CurrentCulture = culture;
CultureInfo.CurrentUICulture = culture;
}

// Call the next delegate/middleware in the pipeline
return next();
});

app.Run(async (context) =>
{
await context.Response.WriteAsync(
$"Hello {CultureInfo.CurrentCulture.DisplayName}");
});

}
}

//以下2行代码选其一即可让浏览器用utf8来解析数据
context.Response.ContentType = "text/html;charset=UTF-8";
context.Response.Headers.Add("Content-type", "text/html;charset=UTF-8");

http://localhost:7997/?culture=no

using Microsoft.AspNetCore.Http;
using System.Globalization;
using System.Threading.Tasks;

namespace Culture
{
public class RequestCultureMiddleware
{
private readonly RequestDelegate _next;

public RequestCultureMiddleware(RequestDelegate next)
{
_next = next;
}

public Task Invoke(HttpContext context)
{
var cultureQuery = context.Request.Query["culture"];
if (!string.IsNullOrWhiteSpace(cultureQuery))
{
var culture = new CultureInfo(cultureQuery);

CultureInfo.CurrentCulture = culture;
CultureInfo.CurrentUICulture = culture;

}

// Call the next delegate/middleware in the pipeline
return this._next(context);
}
}
}

using Microsoft.AspNetCore.Builder;

namespace Culture
{
public static class RequestCultureMiddlewareExtensions
{
public static IApplicationBuilder UseRequestCulture(
this IApplicationBuilder builder)
{
return builder.UseMiddleware<RequestCultureMiddleware>();
}
}
}

Configure

public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.UseRequestCulture();

app.Run(async (context) =>
{
await context.Response.WriteAsync(
$"Hello {CultureInfo.CurrentCulture.DisplayName}");
});

}
}

UseMiddleware<T>

每个请求的依赖关系

Invoke

Invoke

public class MyMiddleware
{
private readonly RequestDelegate _next;

public MyMiddleware(RequestDelegate next)
{
_next = next;
}

public async Task Invoke(HttpContext httpContext, IMyScopedService svc)
{
svc.MyProperty = 1000;
await _next(httpContext);
}
}

资源