五分钟了解dotnetcore配置框架

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();
    memoryData.Add("Student:Code", "10002385");
    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:

• 主要在docker中使用
  

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(configurationRoot.GetSection("WeixinSetting"));
            services.AddScoped();
            var provider = services.BuildServiceProvider();
            var weixinService = provider.GetService();
            string appId = weixinService.AppId;
            string token = weixinService.Token;
            Console.Read();
        }
    }
    interface IWeixinService
    {
        string AppId { get; }
        string Token { get; }
    }
    class WeixinService: IWeixinService
    {
        IOptions _options;
        public WeixinService(IOptions 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)