ASP.NET CORE 中间件

中间件的简单用法

代码中对于中间件的定义，通过翻看IApplicationBUilder的元数据，发现下面的两处定义对于形参的描述均为middleware,可见对于这两中委托均属于中间件。

public interface IApplicationBuilder
{
    //
    // 摘要:
    //     Adds a middleware delegate to the application's request pipeline.
    //
    // 参数:
    //   middleware:
    //     The middleware delegate.
    //
    // 返回结果:
    //     The Microsoft.AspNetCore.Builder.IApplicationBuilder.
    IApplicationBuilder Use(Func<RequestDelegate, RequestDelegate> middleware);
}

上面这种中间用来进行中间件间的转发，里面根据业务情况来决定处理请求发给哪个中间件。

public static class UseExtensions
{
    //
    // 摘要:
    //     Adds a middleware delegate defined in-line to the application's request pipeline.
    //
    // 参数:
    //   app:
    //     The Microsoft.AspNetCore.Builder.IApplicationBuilder instance.
    //
    //   middleware:
    //     A function that handles the request or calls the given next function.
    //
    // 返回结果:
    //     The Microsoft.AspNetCore.Builder.IApplicationBuilder instance.
    public static IApplicationBuilder Use(this IApplicationBuilder app, Func<HttpContext, Func<Task>, Task> middleware);
}

• 作为终端的中间件

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Run(async context =>
            {
                await context.Response.WriteAsync("This is a middleware");
            });
        }

• 加入两个中间件

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Use(async (context, next) =>
            {
                await next.Invoke();
            });
            app.Run(async context =>
            {
                await context.Response.WriteAsync("This is a middleware");
            });
        }

• 通过匹配路径使用分支

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Map("/tom", app =>
             {
                 app.Run(async context =>
                 {
                     await context.Response.WriteAsync("hello tom");
                 });
             });

            app.Map("/cat", app =>
             {
                 app.Run(async context =>
                 {
                     await context.Response.WriteAsync("hello cat");
                 });
             });

            app.Map("", app =>
            {
                app.Run(async context =>
                {
                    await context.Response.WriteAsync("hello everyone");
                });
            });
        }

• 通过自定义条件使用分支,判断规则按代码顺序判定

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.MapWhen(context =>
            {
                if (context.Request.Path.Value.Contains("dog"))
                    return true;
                return false;
            }, app =>
            {
                app.Run(async context =>
                {
                    await context.Response.WriteAsync("hello dog");
                });
            }
            );

            app.Map("/tom", app =>
             {
                 app.Run(async context =>
                 {
                     await context.Response.WriteAsync("hello tom");
                 });
             });

            app.Map("", app =>
            {
                app.Run(async context =>
                {
                    await context.Response.WriteAsync("hello everyone");
                });
            });
        }

• 嵌套Map + 多段匹配

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Map("/animal", builder =>
             {
                 builder.Map("/dog", builder2 =>
                  {
                      builder2.Run(async context =>
                      {
                          await context.Response.WriteAsync("hello dog");
                      });
                  });
             });

            app.Map("/people/tom", builder =>
            {
                builder.Run(async context =>
                {
                    await context.Response.WriteAsync("hello tom");
                });
            });
        }

• 中间件的短路

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            app.Use(GetRequestSchemeMiddleware);
            app.Use(GetRequestMethodMiddleware);
            app.Use(async (httpContext, func) =>
            {
                await func.Invoke();
            });
            app.Use((httpContext, func) =>
            {
                if (httpContext.Request.Path.Value.Contains("snapped"))
                    return httpContext.Response.WriteAsync("be snapped\r\n");
                return func.Invoke();
            });
            app.Run(async context =>
            {
                await context.Response.WriteAsync("Terminal\r\n");
            });
        }

public static Task GetRequestSchemeMiddleware(HttpContext context,Func<Task> next)
        {
            string line = $"Request Method:{context.Request.Scheme}";
            next.Invoke();
            return context.Response.WriteAsync(line + "\r\n");
        }
public static async Task GetRequestMethodMiddleware(HttpContext context, Func<Task> next)
        {
            string line = $"Request Method:{context.Request.Method}";
            await next.Invoke();
            await context.Response.WriteAsync(line + "\r\n");
        }