dotnetcore配置框架简介

一、前言

配置的本质就是字符串的键值对，微软的一系列接口其实就是对这些键值对字符串的抽象。

二、基本类型

2.1、Nuget包

• Microsoft.Extensions.Configuration.Abstractions
• Microsoft.Extensions.Configuration

2.2、抽象接口

• IConfiguration

• 提供了查询、设置配置项、监控变化等方法

• IConfigurationRoot

• 在IConfiguration接口基础上，增加了 Reload 方法强制从provider中重新加载配置值

• IConfigurationSection

• 对配置节点的抽象

• IConfigurationBuilder

• 根据提供的数据源注册并构建IConfiguration

• IConfigurationSource

• 对数据源的抽象，例如Json、xml、环境变量、内存变量等

• IConfigurationProvider

• 规定了配置项的获取、设置、重载等统一的行为

三、基本配置

注：各种配置方式的目的是在控制台中输出以下内容，如下图：

3.1、加载内存中的配置

• 需要引入包：Microsoft.Extensions.Configuration
• 主要方法：builder.AddInMemoryCollection()

static void Main(string[] args)
{
    IConfigurationBuilder builder = new ConfigurationBuilder();
    var memoryData = new Dictionary<string, string>();
    memoryData.Add("Student:Code", "");
    memoryData.Add("Student:Name", "LiuSan");

    builder.AddInMemoryCollection(memoryData);
    IConfigurationRoot configurationRoot = builder.Build();
    IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

    Console.WriteLine($"Code:{configurationSection["Code"]}");
    Console.WriteLine($"Name:{configurationSection["Name"]}");        

    Console.Read();
}

3.2、加载环境变量中的配置

• 需要引入包：Microsoft.Extensions.Configuration.EnvironmentVariables
• 主要方法：builder.AddEnvironmentVariables()
• 环境变量中层级关系使用 __ 代替 :

 static void Main(string[] args)
 {
     IConfigurationBuilder builder = new ConfigurationBuilder();
     builder.AddEnvironmentVariables();
     IConfigurationRoot configurationRoot = builder.Build();
     IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

     Console.WriteLine($"Code:{configurationSection["Code"]}");
     Console.WriteLine($"Name:{configurationSection["Name"]}");

     Console.Read();
 }

3.3、加载命令行中的配置

• 需要引入包：Microsoft.Extensions.Configuration.CommandLine
• 主要方法：builder.AddCommandLine(args)
• 命令行中使用--表示配置项，层级关系使用:

 static void Main(string[] args)
 {
     IConfigurationBuilder builder = new ConfigurationBuilder();
     builder.AddCommandLine(args);
     IConfigurationRoot configurationRoot = builder.Build();
     IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

     Console.WriteLine($"Code:{configurationSection["Code"]}");
     Console.WriteLine($"Name:{configurationSection["Name"]}");

     Console.Read();
 }

3.4、加载Json中的配置

• 需要引入包：Microsoft.Extensions.Configuration.Json
• 主要方法：builder.AddJsonFile("appsettings.json")

 static void Main(string[] args)
 {
     IConfigurationBuilder builder = new ConfigurationBuilder();
     builder.AddJsonFile("appsettings.json");
     IConfigurationRoot configurationRoot = builder.Build();
     IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

     Console.WriteLine($"Code:{configurationSection["Code"]}");
     Console.WriteLine($"Name:{configurationSection["Name"]}");

     Console.Read();
 }

3.5、加载xml中的配置

• 需要引入包：Microsoft.Extensions.Configuration.Xml
• 主要方法：builder.AddXmlFile("appsettings.xml")
• xml中不会读取最外层，所以Section必需从第二层开始

 static void Main(string[] args)
 {
     IConfigurationBuilder builder = new ConfigurationBuilder();
     builder.AddXmlFile("appsettings.xml");
     IConfigurationRoot configurationRoot = builder.Build();
     IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

     Console.WriteLine($"Code:{configurationSection["Code"]}");
     Console.WriteLine($"Name:{configurationSection["Name"]}");

     Console.Read();
 }

四、高级配置

4.1、将配置绑定至强对象

• 需要引入包：Microsoft.Extensions.Configuration.Binder
• 主要方法：configurationRoot.GetSection("Student").Bind(student)

 class Program
     {
         static void Main(string[] args)
         {
             IConfigurationBuilder builder = new ConfigurationBuilder();
             builder.AddJsonFile("appsettings.json");
             IConfigurationRoot configurationRoot = builder.Build();

             var student = new Student();
             configurationRoot.GetSection("Student").Bind(student);

             Console.WriteLine($"Code:{student.Code}");
             Console.WriteLine($"Name:{student.Name}");

             Console.Read();
         }
     }

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

         public string Name { get; set; }
     }

4.2、IOptions

• 需要引入包：Microsoft.Extensins.Options
• 需要引入包：Microsoft.Extensions.Options.ConfigurationExtensions
• 本质其实就是将一个Section配置节点映射到一个实体对象

 class Program
     {
         static void Main(string[] args)
         {
             IConfigurationBuilder builder = new ConfigurationBuilder();
             builder.AddJsonFile("appsettings.json");
             IConfigurationRoot configurationRoot = builder.Build();

             IServiceCollection services = new ServiceCollection();
             services.Configure<WeixinOptions>(configurationRoot.GetSection("WeixinSetting"));
             services.AddScoped<IWeixinService, WeixinService>();

             var provider = services.BuildServiceProvider();
             var weixinService = provider.GetService<IWeixinService>();
             string appId = weixinService.AppId;
             string token = weixinService.Token;

             Console.Read();
         }
     }

     interface IWeixinService
     {
         string AppId { get; }
         string Token { get; }
     }

     class WeixinService: IWeixinService
     {
         IOptions<WeixinOptions> _options;
         public WeixinService(IOptions<WeixinOptions> options)
         {
             _options = options;
         }

         public string AppId { get => _options.Value.AppId; }
         public string Token { get => _options.Value.Token;}
     }

     class WeixinOptions
     {
         public string AppId { get; set; }

         public string Token { get; set; }
     }

4.3、热更新

• IConfigurationBuilder添加数据源时设置reloadOnChange=true
• 监听的核心方法：var token = configurationRoot.GetReloadToken()

 static void Main(string[] args)
         {
             IConfigurationBuilder builder = new ConfigurationBuilder();
             builder.AddJsonFile("appsettings.json", optional:false, reloadOnChange:true);
             IConfigurationRoot configurationRoot = builder.Build();
             IConfigurationSection configurationSection = configurationRoot.GetSection("Student");

             var token = configurationRoot.GetReloadToken();
             ChangeToken.OnChange(() => configurationRoot.GetReloadToken(), () =>
             {
                 Console.WriteLine("配置发生改变了...");
                 Console.WriteLine($"Code:{configurationSection["Code"]}");
                 Console.WriteLine($"Name:{configurationSection["Name"]}");
             });           

             Console.Read();
         }

五、总结

• 配置就是key-value键值对字符串
• IConfiguration和IConfigurationRoot是对键值对的抽象
• IConfigurationBuilder用于构建IConfiguration和IConfigurationRoot
• IConfigurationSource是对数据源的抽象
• IConfigurationProvider将不同来源的IConfigurationSource 转为统一的模型
• IOptions方便将不同的配置节点(Path)映射为对应的强类型对象
• IConfigurationBuilder添加多个数据源（IConfigurationSource）后，如果key重名，则以最后一个配置为准(覆盖前面)

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