配置系统

- Microsoft.Extensions.Configuration
- Microsoft.Extensions.Configuration.Json
- Microsoft.Exensions.Configuration.CommandLine
- Microsoft.Extensions.Options
- Microsoft.Extensions.Binder

```mindmap
# 配置管理
## 基础式
### 配置文件
### 命令行
### 环境变量
### 多配制源
## 选项式
```
# 1.基础式

## 1.1 配置文件
```java
using Microsoft.Extensions.Configuration;

//配置创建器
ConfigurationBuilder configBuilder = new ConfigurationBuilder();
//添加一个待解析的JSON文件，option，为true时文件不存在也不会报错；reloadOnChange:文件修改是否重新加载配置
configBuilder.AddJsonFile("config.json", optional: false, reloadOnChange: false);
//通过它读取配置项
IConfigurationRoot config = configBuilder.Build();
string name = config["name"];
string proxyAddress = config.GetSection("proxy:address").Value;//配置分级方式的读取

```

## 1.2 命令行读取配置
适合容器化的运行环境
```java
//## NuGet安装 Microsoft.Exensions.Configuration.CommandLine
ConfigurationBuilder configBuilder = new ConfigurationBuilder();
configBuilder.AddCommandLine(args);
IConfigurationRoot config = configBuilder.Build();
string server = config["server"];
Console.WriteLine($"server:{server}");
```

## 1.3 从环境变量读取配置
```java
//NuGet安装Microsoft.Exensions.Configuration.EnvironmentVariables
ConfigurationBuilder configBuilder = new ConfigurationBuilder();
//AddEnvironmentVariables存在无参数和prefix参数两个版本
//无参数表示将所有环境变量加载，prefix表示将带有某前缀的环境便令读入
configBuilder.AddEnvironmentVariables("TEST_");
IConfigurationRoot configRoot = configBuilder.Build();
string name = configRoot["Name"];//环境变量TEST_Name
Console.WriteLine(name);
```
## 1.4 多配制源
场景：开发的软件可以从服务器中读取配置，但是我们想临时更改配置又不影响其他用户，并且日后不想用了可以直接删除本地配置即可。
```java
ConfigurationBuilder configBuilder = new ConfigurationBuilder();
//增加json、环境变量、命令行配置
//后添加的配置程序覆盖之前的配置程序
configBuilder.AddJsonFile("appsettings.json")
    .AddEnvironmentVariables("Test1_").AddCommandLine(args);
IConfigurationRoot config = configBuilder.Build();
string server = config["Server"];
string userName = config["UserName"];
string password = config["Password"];
string port = config["Port"];
//Console.WriteLine($"server={server},port={port}");
//Console.WriteLine($"userName={userName},password={password}");
//配置源较多的时候，查看配置值来自哪个配置程序
Console.WriteLine(config.GetDebugView());

```

# 选项方式
>i 选项方式可以和依赖注入结合，同时可以实现修改配置后自动刷新。
需要安装Microsoft.Extensions.Options和Microsoft.Extensions.Binder

| 列名 | 列名 | 列名 |
| --- | --- | --- |
| 1 | IOptions\<T> | 配置改变后，不能读取新的值，必须重启程序 |
| 2 | IOptionsMonitor\<T> | 即时改变，易造成前后读取不一致 |
| 3 | IOptionsSnapshot\<T> | 再次进入范围才会读到新值 |

```seq
选项式流程步骤->选项式流程步骤:(1)添加json配置文件
选项式流程步骤->选项式流程步骤:(2)创建配置的模型类
选项式流程步骤->选项式流程步骤:(3)注册与选项相关的服务
选项式流程步骤->选项式流程步骤:(4)使用配置的业务服务
```
- (1)添加json配置文件
```js
{
  "Logging": { "LogLevel": { "Default": "Warning" } },
  "DB": {
    "DbType": "SQLServer",
    "ConnectionString": "Data Source=.;Initial Catalog=DemoDB; Integrated Security=True"
  },
  "Smtp": {
    "Server": "smtp.youzack.com",
    "UserName": "zack",
    "Password": "hello888"
  },
  "AllowedHosts": "*"
}
```
(2)创建配置的模型类
```java
public class DbSettings
{
    public string DbType { get; set; }
    public string ConnectionString { get; set; }
}
public class SmtpSettings
{
    public string Server { get; set; }
    public string UserName { get; set; }
    public string Password { get; set; }
}
```

```java
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

ConfigurationBuilder confi   gBuilder = new ConfigurationBuilder();
configBuilder.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);//reloadOnChange要设置为true
IConfigurationRoot config = configBuilder.Build();
ServiceCollection services = new ServiceCollection();//容器
services.AddOptions()//注册与选项相关的服务
	.Configure<DbSettings>(e=>config.GetSection("DB").Bind(e))//将DB节点的内容绑定到DbSettings上
	.Configure<SmtpSettings>(e => config.GetSection("Smtp").Bind(e));
//上面定义的IOptionsSnapshot<T>为范围，所以Demo不能是单例，因为Demo中需要Option,所以Demo不能比Option声明周期短
services.AddTransient<Demo>();
using (var sp = services.BuildServiceProvider())
{
	while (true)
	{
		using (var scope = sp.CreateScope())//option设置为范围声明周期，在这里，创建一个新范围
		{
			var spScope = scope.ServiceProvider;
			var demo = spScope.GetRequiredService<Demo>();
			demo.Test();
		}
		Console.WriteLine("可以改配置啦");
		Console.ReadKey();
	}
}

```

```java
class Demo
{
    //在构造方法中声明所依赖的类
	private readonly IOptionsSnapshot<DbSettings> optDbSettings;
	private readonly IOptionsSnapshot<SmtpSettings> optSmtpSettings;
	public Demo(IOptionsSnapshot<DbSettings> optDbSettings,
		IOptionsSnapshot<SmtpSettings> optSmtpSettings)
	{
		this.optDbSettings = optDbSettings;
		this.optSmtpSettings = optSmtpSettings;
	}
	public void Test()
	{
		var db = optDbSettings.Value;//通过value属性获取对象具体的值
		Console.WriteLine($"数据库：{db.DbType},{db.ConnectionString}");
		var smtp = optSmtpSettings.Value;
		Console.WriteLine($"Smtp：{smtp.Server},{smtp.UserName},{smtp.Password}");
	}
}
```