ASP.NET Core快速入门（第2章：配置管理）- 学习笔记(转载)

原文地址：https://mp.weixin.qq.com/s?__biz=MjM5NjMzMzE2MA==&mid=2451733443&idx=2&sn=6d01721c55d486df3efaa21dace9de6a&chksm=b13c08c4864b81d23a09f15abe703249d76019c9886509d4d1b73f7d8dd99717d8fee7dc7d91&mpshare=1&scene=1&srcid=&sharer_sharetime=1575242352502&sharer_shareid=03e89b3db7bd7f780e5e6f6aeac19ec0&pass_ticket=RXV14KW7NB%2FaPTT2RIYzlh9XS4HYLkksvZekeGxQBjPoFv3CNqRXbhBdtX512P68#rd

任务9：配置介绍

• 命令行配置

• Json文件配置

• 从配置文件文本到c#对象实例的映射 - Options 与 Bind

• 配置文件热更新

• 框架设计：Configuration

任务10：命令行配置

新建项目CommandLineSample--控制台应用（.NET Core）

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

传入参数

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();
        }
    }
}

项目右键--调试--输入参数：name=mingsonzheng age=18

启动项目

默认参数

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();
        }
    }
}

清空应用程序参数

启动项目

通过PowerShell运行程序，默认参数与传入参数对比

PS D:jessetalkCommandLineSampleCommandLineSampleinDebug
etcoreapp2.1> dotnet CommandLineSample.dll
name: mingsonzheng
age: 18

PS D:jessetalkCommandLineSampleCommandLineSampleinDebug
etcoreapp2.1> dotnet CommandLineSample.dll name=jim age=22
name: jim
age: 22

任务11：Json文件配置

新建项目JsonComfigSample--控制台应用（.NET Core）

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

添加Json文件：项目右键--添加新建项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binDebug目录下，所以默认不会被编译，文件右键属性，修改为始终复制

using System;
using Microsoft.Extensions.Configuration;

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

            Console.ReadLine();
        }
    }
}

启动项目，可以看到class.json被复制到binDebug目录，这样dll就可以读取到class.json文件

读取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");

            // 调用Build之前请确保拷贝的class.json文件没有格式错误
            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();
        }
    }
}

启动项目

任务12：Bind读取配置到C#实例

新建ASP.NET Core Web 应用程序OptionsBindSample，直接选择 空，确定

在Startup.cs中通过依赖注入添加configuration

public IConfiguration Configuration { get; set; }

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

项目右键，新建项，添加一个类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; }
    }
}

项目右键，新建项，添加一个Json文件appsettings.json

为什么取名appsettings.json呢？

因为Program.cs中的CreateDefaultBuilder默认读取一个名为appsettings.json的Json文件并把它的内容添加到配置文件

拷贝前面的内容到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中通过Bind读取配置

app.Run(async (context) =>
{
    var myClass = new Class();
    Configuration.Bind(myClass);// 实现配置文件信息与对象的映射

    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; }

        // 通过依赖注入添加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读取配置

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

启动项目

任务13：在Core Mvc中使用Options

在项目OptionsBindSample新建三个文件夹目录如下

在Controllers文件夹右键，添加一个控制器，默认，HomeController

在Home文件夹右键，添加一个视图，默认，Index

在Startup.cs中注释掉这一段代码，不然会把整个管道提交，只输出这一段

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

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

依赖注入配置添加MVC

services.AddMvc();

使用默认路由

app.UseMvcWithDefaultRoute();

HomeController中通过IOptions方式依赖注入

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;

        // 通过IOptions方式依赖注入
        public HomeController(IOptions<Class> classAccesser)
        {
            _myClass = classAccesser.Value;
        }

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

在Index中定义模型，输出

@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>

注册Class,可以通过Configuration读取到option

services.Configure<Class>(Configuration);

Startup.cs完整代码

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; }

        // 通过依赖注入添加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)
        {
            // 注册Class,可以通过Configuration读取到option
            services.Configure<Class>(Configuration);
            // 依赖注入配置添加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();
            }

            // 使用默认路由
            app.UseMvcWithDefaultRoute();

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

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

启动项目

如果仅仅在视图中使用options的话，HomeController的代码有点多余，可以直接在视图中注入

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();
        }
    }
}

启动项目得到同样结果

任务14：配置的热更新

ASP.NET修改web.config后站点会自动重启实现热更新

ASP.NET Core不同，实现如下：

将Index的这一行

@inject IOptions<OptionsBindSample.Class> ClassAccesser

修改为

@inject IOptionsSnapshot<OptionsBindSample.Class> ClassAccesser

启动项目

修改appsettings的ClassNo为222，保存

  "ClassNo": "222",

刷新网页

实现原理

对比控制台程序JsonComfigSample的Program读取配置文件

            // 第二个参数表示文件不存在时是否抛异常
            // 第三个参数表示配置文件更新的时候是否重新加载
            var builder = new ConfigurationBuilder()
                .AddJsonFile("class.json",false,true);

而在ASP.NET Core程序OptionsBindSample在Program中的CreateDefaultBuilder的源码实现了

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

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

源码里面实现热更新（165行）

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

由于它是WebHostBuilder的一个扩展函数，所以可以覆盖该方法

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        // 如果业务场景不需要一个线程一直关注配置文件变更，可以关闭热更新
        .ConfigureAppConfiguration(config => { config.AddJsonFile("appsettings.json", false, false); })
        .UseStartup<Startup>();

启动项目，修改配置文件，保存，刷新网页，内容不会热更新

任务15：配置框架设计浅析

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

builder.Add(source);// 将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;
}