ASP.NET Core快速入門(mén)（第2章：配置管理）--學(xué)習(xí)筆記

課程鏈接：http://video.jessetalk.cn/course/explore

良心課程，大家一起來(lái)學(xué)習(xí)哈！

任務(wù)9：配置介紹

命令行配置
Json文件配置
從配置文件文本到c#對(duì)象實(shí)例的映射 - Options 與 Bind
配置文件熱更新
框架設(shè)計(jì)：Configuration

任務(wù)10：命令行配置

新建項(xiàng)目CommandLineSample--控制臺(tái)應(yīng)用（.NET Core）

管理NuGet程序包--下載microsoft.aspnetcore.all

傳入?yún)?shù)

using System;
using Microsoft.Extensions.Configuration;

namespace CommandLineSample
{
    class Program
    {
        static void Main(string[] args)
        {
            var builder = new ConfigurationBuilder()
                .AddCommandLine(args);

            var configuration = builder.Build();

            Console.WriteLine($"name: {configuration ["name"]}");
            Console.WriteLine($"age: {configuration["age"]}");

            Console.ReadLine();
        }
    }
}

項(xiàng)目右鍵--調(diào)試--輸入?yún)?shù)：name=mingsonzheng age=18

啟動(dòng)項(xiàng)目

默認(rèn)參數(shù)

using System;
using System.Collections.Generic;
using Microsoft.Extensions.Configuration;

namespace CommandLineSample
{
    class Program
    {
        static void Main(string[] args)
        {
            var settings = new Dictionary<string, string>
            {
                {"name", "mingsonzheng" },
                {"age", "18" }
            };

            var builder = new ConfigurationBuilder()
                .AddInMemoryCollection(settings)
                .AddCommandLine(args);

            var configuration = builder.Build();

            Console.WriteLine($"name: {configuration ["name"]}");
            Console.WriteLine($"age: {configuration["age"]}");

            Console.ReadLine();
        }
    }
}

清空應(yīng)用程序參數(shù)

啟動(dòng)項(xiàng)目

通過(guò)PowerShell運(yùn)行程序，默認(rèn)參數(shù)與傳入?yún)?shù)對(duì)比

PS D:\jessetalk\CommandLineSample\CommandLineSample\bin\Debug\netcoreapp2.1> dotnet CommandLineSample.dll
name: mingsonzheng
age: 18

PS D:\jessetalk\CommandLineSample\CommandLineSample\bin\Debug\netcoreapp2.1> dotnet CommandLineSample.dll name=jim age=22
name: jim
age: 22

任務(wù)11：Json文件配置

新建項(xiàng)目JsonComfigSample--控制臺(tái)應(yīng)用（.NET Core）

管理NuGet程序包--下載microsoft.aspnetcore.all

添加Json文件：項(xiàng)目右鍵--添加新建項(xiàng)class.json

{
  "ClassNo": "1",
  "ClassDesc": "ASP.NET Core 101",

  "Students": [
    {
      "name": "mingsonzheng",
      "age": "18"
    },
    {
      "name": "jim",
      "age": "28"
    },
    {
      "name": "tom",
      "age": "38"
    }
  ]
}

由于class.json不在bin\Debug目錄下，所以默認(rèn)不會(huì)被編譯，文件右鍵屬性，修改為始終復(fù)制

using System;
using Microsoft.Extensions.Configuration;

namespace JsonComfigSample
{
    class Program
    {
        static void Main(string[] args)
        {
            var builder = new ConfigurationBuilder()
                .AddJsonFile("class.json");

            Console.ReadLine();
        }
    }
}

啟動(dòng)項(xiàng)目，可以看到class.json被復(fù)制到bin\Debug目錄，這樣dll就可以讀取到class.json文件

讀取json文件

using System;
using Microsoft.Extensions.Configuration;

namespace JsonComfigSample
{
    class Program
    {
        static void Main(string[] args)
        {
            var builder = new ConfigurationBuilder()
                .AddJsonFile("class.json");

            // 調(diào)用Build之前請(qǐng)確保拷貝的class.json文件沒(méi)有格式錯(cuò)誤
            var configuration = builder.Build();

            Console.WriteLine($"ClassNo: { configuration["ClassNo"]}");
            Console.WriteLine($"ClassDesc: { configuration["ClassDesc"]}");

            Console.WriteLine("Students");

            Console.Write(configuration["Students:0:name"]);
            Console.WriteLine(configuration["Students:0:age"]);

            Console.Write(configuration["Students:1:name"]);
            Console.WriteLine(configuration["Students:1:age"]);

            Console.Write(configuration["Students:2:name"]);
            Console.WriteLine(configuration["Students:2:age"]);

            Console.ReadLine();
        }
    }
}

啟動(dòng)項(xiàng)目

任務(wù)12：Bind讀取配置到C#實(shí)例

新建ASP.NET Core Web 應(yīng)用程序OptionsBindSample，直接選擇空，確定

在Startup.cs中通過(guò)依賴注入添加configuration

public IConfiguration Configuration { get; set; }

public Startup(IConfiguration configuration)
{
    Configuration = configuration;
}

項(xiàng)目右鍵，新建項(xiàng)，添加一個(gè)類Class.cs

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

namespace OptionsBindSample
{
    public class Class
    {
        public int ClassNo { get; set; }

        public string ClassDesc { get; set; }

        public List<Student> Students { get; set; }

    }

    public class Student
    {
        public string Name { get; set; }

        public string Age { get; set; }
    }
}

項(xiàng)目右鍵，新建項(xiàng)，添加一個(gè)Json文件appsettings.json

為什么取名appsettings.json呢？

因?yàn)镻rogram.cs中的CreateDefaultBuilder默認(rèn)讀取一個(gè)名為appsettings.json的Json文件并把它的內(nèi)容添加到配置文件

拷貝前面的內(nèi)容到appsettings.json

{
  "ClassNo": "1",
  "ClassDesc": "ASP.NET Core 101",

  "Students": [
      {
        "name": "mingsonzheng",
        "age": "18"
      },
      {
        "name": "jim",
        "age": "28"
      },
      {
        "name": "tom",
        "age": "38"
      }
  ]
}

在Startup.cs中通過(guò)Bind讀取配置

app.Run(async (context) =>
{
    var myClass = new Class();
    Configuration.Bind(myClass);// 實(shí)現(xiàn)配置文件信息與對(duì)象的映射

    await context.Response.WriteAsync($"ClassNo: { myClass.ClassNo}");
    await context.Response.WriteAsync($"ClassDesc: { myClass.ClassDesc}");
    await context.Response.WriteAsync($" {myClass.Students.Count } Students");
});

完整Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace OptionsBindSample
{
    public class Startup
    {

        public IConfiguration Configuration { get; set; }

        // 通過(guò)依賴注入添加configuration
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        // 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)
        {
        }

        // 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();
            }

            app.Run(async (context) =>
            {
                var myClass = new Class();
                Configuration.Bind(myClass);// Bind讀取配置

                await context.Response.WriteAsync($"ClassNo: { myClass.ClassNo}");
                await context.Response.WriteAsync($"ClassDesc: { myClass.ClassDesc}");
                await context.Response.WriteAsync($" {myClass.Students.Count } Students");
            });
        }
    }
}

啟動(dòng)項(xiàng)目

任務(wù)13：在Core Mvc中使用Options

在項(xiàng)目OptionsBindSample新建三個(gè)文件夾目錄如下

在Controllers文件夾右鍵，添加一個(gè)控制器，默認(rèn)，HomeController

在Home文件夾右鍵，添加一個(gè)視圖，默認(rèn)，Index

在Startup.cs中注釋掉這一段代碼，不然會(huì)把整個(gè)管道提交，只輸出這一段

//app.Run(async (context) =>
//{
//    var myClass = new Class();
//    Configuration.Bind(myClass);// Bind讀取配置

//    await context.Response.WriteAsync($"ClassNo: { myClass.ClassNo}");
//    await context.Response.WriteAsync($"ClassDesc: { myClass.ClassDesc}");
//    await context.Response.WriteAsync($" {myClass.Students.Count } Students");
//});

依賴注入配置添加MVC

services.AddMvc();

使用默認(rèn)路由

app.UseMvcWithDefaultRoute();

HomeController中通過(guò)IOptions方式依賴注入

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;

namespace OptionsBindSample.Controllers
{
    public class HomeController : Controller
    {
        private readonly Class _myClass;

        // 通過(guò)IOptions方式依賴注入
        public HomeController(IOptions<Class> classAccesser)
        {
            _myClass = classAccesser.Value;
        }

        public IActionResult Index()
        {
            return View(_myClass);
        }
    }
}

在Index中定義模型，輸出

@model OptionsBindSample.Class
@{
    ViewData["Title"] = "Index";
}

<h2>Index</h2>
<h4>Class No: @Model.ClassNo</h4>
<h4>Class Desc: @Model.ClassDesc</h4>
<h3>
    Students:
</h3>
<div>
    @foreach (var student in Model.Students)
    {
        <span>Name: @student.Name</span>
        <span>Age: @student.Age</span>
    }
</div>

注冊(cè)Class,可以通過(guò)Configuration讀取到option

services.Configure<Class>(Configuration);

Startup.cs完整代碼

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

namespace OptionsBindSample
{
    public class Startup
    {

        public IConfiguration Configuration { get; set; }

        // 通過(guò)依賴注入添加configuration
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        // 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)
        {
            // 注冊(cè)Class,可以通過(guò)Configuration讀取到option
            services.Configure<Class>(Configuration);
            // 依賴注入配置添加MVC
            services.AddMvc();
        }

        // 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();
            }

            // 使用默認(rèn)路由
            app.UseMvcWithDefaultRoute();

            //app.Run(async (context) =>
            //{
            //    var myClass = new Class();
            //    Configuration.Bind(myClass);// Bind讀取配置

            //    await context.Response.WriteAsync($"ClassNo: { myClass.ClassNo}");
            //    await context.Response.WriteAsync($"ClassDesc: { myClass.ClassDesc}");
            //    await context.Response.WriteAsync($" {myClass.Students.Count } Students");
            //});
        }
    }
}

啟動(dòng)項(xiàng)目

如果僅僅在視圖中使用options的話，HomeController的代碼有點(diǎn)多余，可以直接在視圖中注入

Index

@using Microsoft.Extensions.Options;
@inject IOptions<OptionsBindSample.Class> ClassAccesser
@{
    ViewData["Title"] = "Index";
}

<h2>Index</h2>
<h4>Class No: @ClassAccesser.Value.ClassNo</h4>
<h4>Class Desc: @ClassAccesser.Value.ClassDesc</h4>
<h3>
    Students:
</h3>
<div>
    @foreach (var student in ClassAccesser.Value.Students)
    {
        <span>Name: @student.Name</span>
        <span>Age: @student.Age</span>
    }
</div>

HomeController

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;

namespace OptionsBindSample.Controllers
{
    public class HomeController : Controller
    {
        public IActionResult Index()
        {
            return View();
        }
    }
}

啟動(dòng)項(xiàng)目得到同樣結(jié)果

任務(wù)14：配置的熱更新

ASP.NET修改web.config后站點(diǎn)會(huì)自動(dòng)重啟實(shí)現(xiàn)熱更新

ASP.NET Core不同，實(shí)現(xiàn)如下：

將Index的這一行

@inject IOptions<OptionsBindSample.Class> ClassAccesser

修改為

@inject IOptionsSnapshot<OptionsBindSample.Class> ClassAccesser

啟動(dòng)項(xiàng)目

修改appsettings的ClassNo為222，保存

  "ClassNo": "222",

刷新網(wǎng)頁(yè)

實(shí)現(xiàn)原理

對(duì)比控制臺(tái)程序JsonComfigSample的Program讀取配置文件

            // 第二個(gè)參數(shù)表示文件不存在時(shí)是否拋異常
            // 第三個(gè)參數(shù)表示配置文件更新的時(shí)候是否重新加載
            var builder = new ConfigurationBuilder()
                .AddJsonFile("class.json",false,true);

而在ASP.NET Core程序OptionsBindSample在Program中的CreateDefaultBuilder的源碼實(shí)現(xiàn)了

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>();

WebHost源碼：
https://github.com/aspnet/MetaPackages/blob/master/src/Microsoft.AspNetCore/WebHost.cs

源碼里面實(shí)現(xiàn)熱更新（165行）

config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
      .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);

由于它是WebHostBuilder的一個(gè)擴(kuò)展函數(shù)，所以可以覆蓋該方法

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        // 如果業(yè)務(wù)場(chǎng)景不需要一個(gè)線程一直關(guān)注配置文件變更，可以關(guān)閉熱更新
        .ConfigureAppConfiguration(config => { config.AddJsonFile("appsettings.json", false, false); })
        .UseStartup<Startup>();

啟動(dòng)項(xiàng)目，修改配置文件，保存，刷新網(wǎng)頁(yè)，內(nèi)容不會(huì)熱更新

任務(wù)15：配置框架設(shè)計(jì)淺析

var builder = new ConfigurationBuilder();// 初始化Builder

builder.Add(source);// 將source添加到Builder
=>
JsonConfigurationSource source = new
JsonConfigurationSource()
{
    Path = "settings.json";
};

var configurationRoot = builder.Build();// Build
=>
foreach(var source in sources)
{
    var provider = source.Build();
    providers.add(provider);
}
return new ConfigurationRoot(providers);

configurationRoot["Key"]// Use
=>
foreach(var provider in providers.Reverse())
{
    string value;
    provider.TryGet(Key, out Value)
    return value;
}