ASP.NET Core 2.2 基础知识(七) 选项模式-白红宇

ASP.NET Core 2.2 基础知识(七) 选项模式

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发布时间：2019-06-22

本文共 3929 字，大约阅读时间需要 13 分钟。

原文:

承接上一篇配置,

选项模式是专门用类来表示相关配置的服务.

基本选项配置

新建一个选项类,该类必须是包含无参数的构造函数的非抽象类.

public class MyOptions    {        public MyOptions()        {            Id = 1;            Name = "refuge";        }        public int Id { get; set; }        public string Name { get; set; }    }

添加到服务容器,并绑定到配置:

public class Startup    {        ......        public IConfiguration Configuration { get; }        public void ConfigureServices(IServiceCollection services)        {            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);            services.Configure
     
      (Configuration);        }        ......    }

测试控制器:

[Route("api/[controller]/[action]")]    [ApiController]    public class TestController : ControllerBase    {        private readonly IOptions
     
       _options;        public TestController(IOptions
      
        options)        {            _options = options;            _config = config;        }        public MyOptions Get()        {            return _options.Value;        }    }

结果:

通过委托配置选项

public void ConfigureServices(IServiceCollection services)        {            services.Configure
     
      (options =>            {                //这些值会替代 MyOptions 构造函数中设置的值.                //原因很简单,肯定是对象创建了,才会执行这个委托.                options.Id = 2;                options.Name = "refuge2";            });        }

通过文件配置简单选项

新建一个json文件:

{  "Id": 3,  "Name": "refuge3"}

public void ConfigureServices(IServiceCollection services)        {            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);            ConfigurationBuilder builder = new ConfigurationBuilder();            IConfigurationRoot config = builder.AddJsonFile(path: @"E:\Git\Source\Repos\MyOption\Demo1\jsonconfig.json", optional: true, reloadOnChange: true).Build();            services.Configure
     
      (config);        }

还可以读取文件中的某个节点配置简单选项

修改 json 文件,增加 subsection 节点.

{  "Id": 3,  "Name": "refuge3",  "SubSection": {    "Id": 4,    "Name": "refuge4"  } }

public void ConfigureServices(IServiceCollection services)        {            ConfigurationBuilder builder = new ConfigurationBuilder();            IConfigurationRoot config = builder.AddJsonFile(@"E:\Git\Source\Repos\MyOption\Demo1\jsonconfig.json", true, true).Build();            services.Configure
     
      (config.GetSection("subsection"));        }

上面这些例子中的获取到的 MyOptions 对象都是单例的.比如通过文件配置简单选项,即使 AddJsonFile 方法最后一个参数是 true ,配置数据也不会更新.要实现更新需要使用下面这个接口.

通过 IOptionsSnapshot 重新加载配置数据

修改 TestController :

[Route("api/[controller]/[action]")]    [ApiController]    public class TestController : ControllerBase    {        private readonly IOptionsSnapshot
     
       _options;        public TestController(IOptionsSnapshot
      
        options)        {            _options = options;                   }

public MyOptions Get()        {            return _options.Value;        }     }

第一次请求:

修改 json 文件后,刷新页面

通过别名配置选项

public void ConfigureServices(IServiceCollection services)        {            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);            services.Configure
     
      ("option1", Configuration);            services.Configure
      
       ("option2", options =>            {                options.Id = 6;                options.Name = "refuge6";            });        }

修改 TestController

[Route("api/[controller]/[action]")]    [ApiController]    public class TestController : ControllerBase    {        private readonly IOptionsSnapshot
     
       _options;        public TestController(IOptionsSnapshot
      
        options)        {            _options = options;        }        public IEnumerable
       
         Get()        {            for (int i = 1; i < 3; i++)            {                yield return _options.Get("option" + i);            }        }    }