# 第4章：ASP.NET Core HTTP介绍
#### 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.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"]);
});
}
```
启动HelloCore，输出结果\
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.cs
```
app.Run(async (context) =>
{
// await context.Response.WriteAsync("Hello World!");
// JsonFile
//await context.Response.WriteAsync(configuration["ConnectionStrings:DefaultConnection"]);
// CommandLine
await context.Response.WriteAsync($"name={configuration["name"]}");
});
```
设置应用程序参数
启动HelloCore，输出结果\
#### 任务25：IHostEnvironment和 IApplicationLifetime介绍
Startup.cs
```
app.Run(async (context) =>
{
await context.Response.WriteAsync($"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）：
我心中的ASP.NET Core 新核心对象WebHost（二）：
#### 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
```
```
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
#### 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>
_list = new List>();
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 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
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()
);
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
**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)
```