# 模块二 基础巩固 配置
## 2.2.3 核心模块--配置
* IConfiguration
* Options
ASP.NET Core 中的配置：
### IConfiguration
* IConfiguration 的使用
* 层级对象配置到 key-value 键值对转换
* 通过环境变量修改日志级别
* 通过命令行修改日志级别
#### IConfiguration 的使用
appsettings.json
```
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
```
新增 ConfigController.cs
```
namespace HelloApi.Controllers
{
[ApiController]
[Route("[controller]")]
public class ConfigController : Controller
{
private readonly IConfiguration _configuration;
public ConfigController(IConfiguration configuration)
{
_configuration = configuration;
}
[HttpGet]
public IActionResult GetConfigurations()
{
var result = new List();
foreach (var key in _configuration.AsEnumerable())
{
result.Add($"Key: {key.Key}, value: {key.Value}");
}
return Ok(result);
}
}
}
```
启动程序，访问：
不仅得到 appsettings.json 的配置， 还可以得到环境变量配置
可以在 ConfigureAppConfiguration 中清除所有配置，再添加自己需要的配置，后面添加的配置会覆盖前面的配置
```
.ConfigureAppConfiguration((hostingContext, config) =>
{
config.Sources.Clear();
var env = hostingContext.HostingEnvironment;
config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
})
```
启动程序，访问：
这样可以得到自己添加的配置
#### 层级对象配置到 key-value 键值对转换
appsettings.json
```
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
```
通过冒号读取下一级配置（Windows），Linux 上通过下划线
```
[HttpGet]
public IActionResult GetConfigurations()
{
var result = new List();
//foreach (var key in _configuration.AsEnumerable())
//{
// result.Add($"Key: {key.Key}, value: {key.Value}");
//}
return Content(string.Format("Default Log Level: {0}", _configuration["Logging:LogLevel:Default"]));
}
```
启动程序，输出如下：
```
Default Log Level: Debug
```
#### 通过环境变量修改日志级别
在 launcSettings.json 中添加 Trace 日志级别
```
"environmentVariables": {
"ASPNETCORE_ENVIRONMENT": "Development",
"Logging__LogLevel__Default": "Trace"
}
```
在 CreateHostBuilder 的时候添加环境变量配置
```
config.AddEnvironmentVariables();
```
启动程序，输出如下：
```
Default Log Level: Trace
```
#### 通过命令行修改日志级别
CreateHostBuilder
```
config.AddCommandLine(source =>
{
source.Args = args;
});
```
在命令行中设置
```
set Logging__LogLevel__Default=Warning
```
### Options
* 通过 ConfigurationBinder 操作 Options
* 通过 Configure 绑定 Option
#### 通过 ConfigurationBinder 操作 Options
新建 MyOption.cs
```
namespace HelloApi
{
public class MyOption
{
public string Name { get; set; }
public int Age { get; set; }
}
}
```
在 appsettings.json 中新增一个节点
```
"MyOption": {
"Name": "Mingson",
"Age": 25
},
```
在 ConfigureServices 中绑定
```
var myOption = new MyOption();
Configuration.GetSection("MyOption").Bind(myOption);
// 单例注入到全局中
services.AddSingleton(myOption);
```
在 ConfigController 中注入，与获取
```
private readonly MyOption _myOption;
public ConfigController(IConfiguration configuration, MyOption myOption)
{
_configuration = configuration;
_myOption = myOption;
}
[HttpGet("option")]
public IActionResult GetOption()
{
return Ok(_myOption);
}
```
启动程序，访问：
输出如下：
```
{"name":"Mingson","age":25}
```
通过 Get 的方式
```
myOption = Configuration.GetSection("MyOption").Get();
```
#### 通过 Configure 绑定 Option
IOptions
* IOptions 被注册为 singletone，不支持为可命名的配置
* IOptionsSnapshot 被注册为 scoped，支持为可命名的配置
* IOptionsMonitor 被注册为 singletone，会被通知，支持重载配置，支持为可命名的配置
**IOptions**
```
// 直接注入到容器中
services.Configure(Configuration.GetSection("MyOption"));
```
通过 IOptions 注入
```
public ConfigController(IConfiguration configuration, IOptions myOption)
{
_configuration = configuration;
_myOption = myOption.Value;
}
```
启动程序可以得到同样的输出
**IOptionsSnapshot**
```
public ConfigController(IConfiguration configuration, IOptionsSnapshot myOption)
{
_configuration = configuration;
_myOption = myOption.Value;
}
```
启动程序，修改配置，刷新浏览器，可以获取到修改后的配置
**可命名的配置**
appsettings.json
```
"Jack": {
"Name": "Jack",
"Age": 16
},
"Peter": {
"Name": "Peter",
"Age": 18
}
```
MyOption.cs
```
public const string PETER = "Peter";
public const string JACK = "Jack";
```
ConfigureServices
```
services.Configure("Peter", Configuration.GetSection("Peter"));
services.Configure("Jack", Configuration.GetSection("Jack"));
```
ConfigController
```
_myOption = myOption.Get(MyOption.PETER);
_myOption = myOption.Get(MyOption.JACK);
```
启动程序即可读取不同命名的配置
**IOptionsMonitor**
```
public ConfigController(IConfiguration configuration, IOptionsMonitor myOption)
{
_configuration = configuration;
_myOption = myOption.CurrentValue;
// 配置变化处理
myOption.OnChange(option =>
{
});
}
```
#### option 验证
**属性验证标签**
```
namespace HelloApi
{
public class MyConfigOptions
{
public const string MyConfig = "MyConfig";
[RegularExpression(@"^[a-zA-Z''-'\s]{1,40}$")]
public string Key1 { get; set; }
[Range(0, 1000, ErrorMessage = "Value for {0} must be between {1} and {2}.")]
public int Key2 { get; set; }
public int Key3 { get; set; }
}
}
```
**绑定后校验**
ConfigureServices
```
services.AddOptions().Bind(Configuration.GetSection("MyOption")).ValidateDataAnnotations();
```
MyOption
```
[Range(1, 20)]
public int Age { get; set; }
```
启动程序，输出如下：
```
OptionsValidationException: DataAnnotation validation failed for members: 'Age' with the error: 'The field Age must be between 1 and 20.'.
```
#### PostConfigure
当配置被读取出来的时候会被执行
```
services.PostConfigure(option =>
{
if (option.Age == 20)
{
option.Age = 19;
}
});
```
### GitHub源码链接：