第4章：ASP.NET Core HTTP介绍

学习分享丨作者 / 郑子铭丨公众号 / DotNet NB / CloudNative NB

任务22：课程介绍

1.HTTP 处理过程
2.WebHost 的配置与启动
3.Middleware 与管道
4.Routing MiddleWare 介绍

任务23：Http请求的处理过程

任务24：WebHost的配置

1.覆盖配置文件
2.更改启动URL
3.IHostingEnvironment
4.IApplicationLifetime
5.dotnet watch run

dotnet new web

settings.json

{
    "ConnectionStrings":{
        "DefaultConnection":"Server=...;Database=...;"
    }
}

Program.cs

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration(configureDelegate=>{
                configureDelegate.AddJsonFile("settings.json");
            })
            .UseStartup<Startup>();

Startup.cs

using Microsoft.Extensions.Configuration;

public void Configure(IApplicationBuilder app, IHostingEnvironment env, IConfiguration configuration)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.Run(async (context) =>
            {
                // await context.Response.WriteAsync("Hello World!");
                // JsonFile
                await context.Response.WriteAsync(configuration["ConnectionStrings:DefaultConnection"]);
            });
        }

Program.cs

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration(configureDelegate => {
                    //configureDelegate.AddJsonFile("settings.json");
                    configureDelegate.AddCommandLine(args);
                })
                //.UseUrls("http://localhost:5001")
                .UseStartup<Startup>();

Startup.cs

            app.Run(async (context) =>
            {
                // await context.Response.WriteAsync("Hello World!");
                // JsonFile
                //await context.Response.WriteAsync(configuration["ConnectionStrings:DefaultConnection"]);
                // CommandLine
                await context.Response.WriteAsync($"name={configuration["name"]}");
            });

设置应用程序参数

任务25：IHostEnvironment和 IApplicationLifetime介绍

Startup.cs

app.Run(async (context) =>
            {
                await context.Response.WriteAsync($"ContentRootPath = {env.ContentRootPath}");
                await context.Response.WriteAsync($"EnvironmentName = {env.EnvironmentName}");
                await context.Response.WriteAsync($"WebRootPath = {env.WebRootPath}");
            });

启动HelloCore，输出结果

Startup.cs

        public void Configure(IApplicationBuilder app, IHostingEnvironment env, IConfiguration configuration, IApplicationLifetime applicationLifetime)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            applicationLifetime.ApplicationStarted.Register(() =>
            {
                Console.WriteLine("Started");
            });

            applicationLifetime.ApplicationStopped.Register(() =>
            {
                Console.WriteLine("Stopped");
            });

            applicationLifetime.ApplicationStopped.Register(() =>
            {
                Console.WriteLine("Stopped");
            });

            app.Run(async (context) =>
            {                
                await context.Response.WriteAsync($"ContentRootPath = {env.ContentRootPath}");
                await context.Response.WriteAsync($"EnvironmentName = {env.EnvironmentName}");
                await context.Response.WriteAsync($"WebRootPath = {env.WebRootPath}");
            });
        }

启动HelloCore，输出结果

我心中的ASP.NET Core 新核心对象WebHost（一）：

http://www.jessetalk.cn/2017/11/11/aspnet-core-object-webhost/#comment-194

我心中的ASP.NET Core 新核心对象WebHost（二）：

http://www.jessetalk.cn/2017/11/14/aspnet-core-object-webhost-build/

任务26：dotnet watch run 和attach到进程调试

New Terminal

dotnet new web --name HelloCore

F5 Start Debug

在csproj 的 ItemGroup 添加引用

<DotNetCliToolReference Include="Microsoft.DotNet.Watcher.Tools" Version="2.0.0" />

New Terminal

dotnet restore
dotnet watch run

修改代码保存后会自动重启

浏览器刷新即可看到更新结果

attach到进程调试

任务27：Middleware管道介绍

1.Middleware 与管道的概念
2.用 Middleware 来组成管道实践
3.管道的实现机制（RequestDelegate 与 ApplicationBuilder）

startup.cs

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            // 添加一个中间件，传一个名字为next的request delegate
            app.Use(async (context,next)=>{
                await context.Response.WriteAsync("1: before start...");
                await next.Invoke();
            });

            // 接收一个RequestDelegate，返回一个RequestDelegate
            app.Use(next=>{
                return (context)=>{
                    context.Response.WriteAsync("2: in the middle of start..");
                    return next(context);
                };
            });

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("3: start...");
            });
        }

启动项目，输出结果

// 如果不调用next，则管道终止，不会输出"3: start..."
            app.Use(next=>{
                return (context)=>{
                    return context.Response.WriteAsync("2: in the middle of start..");
                    //return next(context);
                };
            });

        // 使用Map构建路由，通过localhost:5000/task访问
        app.Map("/task", taskApp=>{
            taskApp.Run(async context=>{
                await context.Response.WriteAsync("this is a task");
            });
        });

        // 添加一个中间件，传一个名字为next的request delegate
        app.Use(async (context,next)=>{
            await context.Response.WriteAsync("1: before start...");
            await next.Invoke();
        });

        // 接收一个RequestDelegate，返回一个RequestDelegate
        // 如果不调用next，则管道终止，不会输出"3: start..."
        app.Use(next=>{
            return (context)=>{
                context.Response.WriteAsync("2: in the middle of start..");
                return next(context);
            };
        });

        app.Run(async (context) =>
        {
            await context.Response.WriteAsync("3: start...");
        });

访问 https://localhost:5001/task

任务28：RequestDelegate管道实现思路

1.RequestDelegate
2.ApplicationBuilder：多个RequestDelegate拼接

// 添加一个中间件，传一个名字为next的RequestDelegate
app.Use(async (context,next)=>{
    await context.Response.WriteAsync("1: before start...");// 完成自己处理
    await next.Invoke();// 调用下一步
});

// 封装一个function交给ApplicationBuilder处理
app.Use(next=>{
    return (context)=>{
        context.Response.WriteAsync("2: in the middle of start..");
        return next(context);
    };
});

任务29：自己动手构建RequestDelegate管道

新建一个控制台程序

dotnet new console --name MyPipeline

新建一个类RequestDelegate.cs

using System;
using System.Threading.Tasks;

namespace MyPipeline
{
    public delegate Task RequestDelegate(Context context);
}

新建一个类Context.cs

using System;
using System.Threading.Tasks;

namespace MyPipeline
{
    public class Context
    {
        
    }
}

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace MyPipeline
{
    class Program
    {
        public static List<Func<RequestDelegate,RequestDelegate>> 
        _list = new List<Func<RequestDelegate, RequestDelegate>>();
        static void Main(string[] args)
        {
            Use(next=>{
                return context=>{
                    Console.WriteLine("1");
                    return next.Invoke(context);
                };
            });

            Use(next=>{
                return context=>{
                    Console.WriteLine("2");
                    return next.Invoke(context);
                };
            });

            RequestDelegate end = (Context)=>{
                Console.WriteLine("end...");
                return Task.CompletedTask;
            };

            _list.Reverse();
            foreach(var middleware in _list)
            {
                end = middleware.Invoke(end);
            }

            end.Invoke(new Context());
            Console.ReadLine();
        }

        public static void Use(Func<RequestDelegate,RequestDelegate> middleware)
        {
            _list.Add(middleware);
        }
    }
}

在任何一个Middleware可以结束管道

            Use(next=>{
                return context=>{
                    Console.WriteLine("1");
                    //return next.Invoke(context);
                    return Task.CompletedTask;// 结束管道调用，只输出1
                };
            });

任务30：RoutingMiddleware介绍以及MVC引入

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;

namespace HelloCore
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRouting();// 添加依赖注入配置
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

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

            // 通过localhost:5000/action访问
            app.UseRouter(builder=>builder.MapGet("action", async context=>{
                await context.Response.WriteAsync("this is a action");
            }));

            // 使用Map构建路由，通过localhost:5000/task访问
            app.Map("/task", taskApp=>{
                taskApp.Run(async context=>{
                    await context.Response.WriteAsync("this is a task");
                });
            });

            // 添加一个中间件，传一个名字为next的request delegate
            app.Use(async (context,next)=>{
                await context.Response.WriteAsync("1: before start...");
                await next.Invoke();
            });

            // 如果不调用next，则管道终止，不会输出"3: start..."
            app.Use(next=>{
                return (context)=>{
                    return context.Response.WriteAsync("2: in the middle of start..");
                    //return next(context);
                };
            });

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("3: start...");
            });
        }
    }
}

访问 https://localhost:5001/action

使用UseRouter方法2

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;

namespace HelloCore
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRouting();// 添加依赖注入配置
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

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

            // 使用UseRouter方法2
            // 通过localhost:5000/action访问
            RequestDelegate handler = context=>context.Response.WriteAsync("this is a action");
            var route = new Route(
                new RouteHandler(handler),
                "action",
                app.ApplicationServices.GetRequiredService<IInlineConstraintResolver>()
            );

            app.UseRouter(route);

            // 使用UseRouter方法1
            // 通过localhost:5000/action访问
            app.UseRouter(builder=>builder.MapGet("action", async context=>{
                await context.Response.WriteAsync("this is a action");
            }));

            // 使用Map构建路由，通过localhost:5000/task访问
            app.Map("/task", taskApp=>{
                taskApp.Run(async context=>{
                    await context.Response.WriteAsync("this is a task");
                });
            });

            // 添加一个中间件，传一个名字为next的request delegate
            app.Use(async (context,next)=>{
                await context.Response.WriteAsync("1: before start...");
                await next.Invoke();
            });

            // 如果不调用next，则管道终止，不会输出"3: start..."
            app.Use(next=>{
                return (context)=>{
                    return context.Response.WriteAsync("2: in the middle of start..");
                    //return next(context);
                };
            });

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync("3: start...");
            });
        }
    }
}

访问 https://localhost:5001/action

RountingMiddleware介绍

var routeHandler = new RouteHandler(context=>context.Response.WriteAsync("test"));

var route = new Route(routeHandler);

new RouteMiddleware(route)

RouteMiddleware.Invoke(httpContext)

_route.RouteAsync(context)

routeMatch(RouteContext)

OnRouteMatched(RouteContext)

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