Web API学习笔记（五）——中间件（Middleware）和HTTP请求管线（Http Request Pipeline）

1.HTTP请求管线（Http Request Pipeline）

2.中间件（Middleware）

2.1概述

1.中间件是HTTP请求管线中使用的一段代码
2.Asp .Net Core应用程序可以有n个中间件
3.中间件的顺序在执行过程中非常重要。

中间件例如：
1.Routing
2.Authentication
3.Add excretion page …

2.2Run(),Use(),Next()和Map()在中间件中的使用

1.Run()方法用于完成中间件的执行
2.Use()方法用于在管线中插入新的中间件
3.Next()方法用于将执行传递给下一个中间件
4.Map()方法用于将中间件映射到特定的URL

2.2.1 Run()方法

添加一个终端中间件委托到应用到请求管线。

IApplicationBuilder.Run(RequestDelegate handler)

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

            app.Run(async (context) =>
            {
    
    
                await context.Response.WriteAsync("hello Run2");
            });


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

2.2.1 Use()&Next()

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1 \n");
            });

            app.Run(async (context) =>
            {
    
    
                await context.Response.WriteAsync("hello Run2");
            });


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1 \n");
                await next();
            });

            app.Run(async (context) =>
            {
    
    
                await context.Response.WriteAsync("hello Run2");
            });


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1 \n");
                await next();
                await context.Response.WriteAsync("hello Use2 \n");
            });

            app.Run(async (context) =>
            {
    
    
                await context.Response.WriteAsync("hello Run2 \n");
            });


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use1-2 \n");
            });

            app.Use(async (context, next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use2-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use2-2 \n");
            });

            app.Run(async (context) =>
            {
    
    
                await context.Response.WriteAsync("hello Run \n");
            });


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use1-2 \n");
            });

            app.Use(async (context, next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use2-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use2-2 \n");
            });

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("request complete \n");
            });

            //app.Run(async (context) =>
            //{
    
    
            //    await context.Response.WriteAsync("hello Run \n");
            //});


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

2.2.3 Map()

基于给定请求路径的匹配对请求管线进行分支。如果请求路径以给定的路径开始，则执行分支。

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use1-2 \n");
            });

            app.Map("/nitish", Cutom);

            app.Use(async (context, next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use2-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use2-2 \n");
            });

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("request complete \n");
            });

            //app.Run(async (context) =>
            //{
    
    
            //    await context.Response.WriteAsync("hello Run \n");
            //});


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

        private void Cutom(IApplicationBuilder app)
        {
    
    
            app.Use(async (context, next) =>
            {
    
    
                await context.Response.WriteAsync("Hello nitish \n");
            });
        }

运行结果：

2.3 自定义中间件

1.创建一个CustomMiddleware1.cs脚本，代码如下

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

namespace MyWebApi
{
    
    
    public class CustomMiddleware1:IMiddleware
    {
    
    

        public async Task InvokeAsync(HttpContext context, RequestDelegate next)
        {
    
    
            await context.Response.WriteAsync("hello file-1 \n");
            await next(context);
            await context.Response.WriteAsync("hello file-2 \n");
        }
    }
}

2.在Startup.cs脚本中ConfigureServices方法中添加一个自定义的临时服务，代码如下

        public void ConfigureServices(IServiceCollection services)
        {
    
    
            services.AddControllers();
            services.AddTransient<CustomMiddleware1>();
        }

2.在Startup.cs脚本中Configure方法中使用自定义的中间件，代码如下

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

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use1-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use1-2 \n");
            });

            app.UseMiddleware<CustomMiddleware1>();

            app.Map("/nitish", Cutom);

            app.Use(async (context, next) =>
            {
    
    
                await context.Response.WriteAsync("hello Use2-1 \n");
                await next();
                await context.Response.WriteAsync("hello Use2-2 \n");
            });

            app.Use(async (context,next) =>
            {
    
    
                await context.Response.WriteAsync("request complete \n");
            });

            //app.Run(async (context) =>
            //{
    
    
            //    await context.Response.WriteAsync("hello Run \n");
            //});


            if (env.IsDevelopment())
            {
    
    
                app.UseDeveloperExceptionPage();
            }


            app.UseRouting();

            app.UseEndpoints(endponits =>
            {
    
    
                endponits.MapControllers();
            });
        }

运行结果：

2.4 验证中间件的使用

之前提到说Routing使用了中间件，接下来我们就以Routing为例来验证
Asp .Net Core源码链接: https://github.com/dotnet/aspnetcore
然后在右上角搜索UseRouting，找到该方法如下图所示：

再搜索EndpointRoutingMiddleware.cs，如下方法
确定UseRouting中使用了中间件next方法。

下一节：链接: Web API学习笔记（六）——路由（Routing）