学习NetCore的配置管理;
目录
- 命令行配置
- Json文件配置
- 配置文件文本至C#对象实例的映射
- 配置文件热更新
- 总结
命令行配置:
打开VS2017,新建NetCore控制台项目;
打开nuget包管理;添加Microsoft.Asp.NetCore.all,或者使用命令nstall-Package Microsoft.AspNetCore.All进行添加;接下来添加系统参数;右键项目属性,调试,如下图:
OK,跑一下就行;控制台显示:
Json文件配置:
接下来学习Json文件配置:新建一个core的控制台项目;同样的通过nuget添加Microsoft>Asp.NetCore.all;添加一个新的json文件,代码如下:
{ "ClassNo": "1", "ClassDesc": "AspNetCore", "Students": [ { "name": "Tom", "age": "8" }, { "name": "jerry", "age": "7" }, { "name": "rose", "age": "18" } ]}
using System;using Microsoft.Extensions.Configuration;namespace JsonConfigSample{ class Program { static void Main(string[] args) { //配置参数 var builder = new ConfigurationBuilder() .AddJsonFile("Class.json"); var configs = builder.Build(); Console.WriteLine($"ClassNo:{configs["ClassNo"]}"); Console.WriteLine($"ClassDesc:{configs["ClassDesc"]}"); Console.WriteLine("Students"); Console.Write($":{configs["Students:0:name"]}"); Console.WriteLine($":{configs["Students:0:age"]}"); Console.Write($":{configs["Students:1:name"]}"); Console.WriteLine($":{configs["Students:1:age"]}"); Console.Write($":{configs["Students:2:name"]}"); Console.WriteLine($":{configs["Students:2:age"]}"); Console.ReadLine(); } }}
最终运行如下图所示:
配置文件文本至C#对象实例的映射:
创建一个空的mvc项目,将上一步的json文件 复制到这个项目中,并且改名为appsettings.json(因为Program.cs 中 BuildWebHost方法中,默认将appsettings.json写入配置)。然后我们创建一个类,名字叫做MyClass;(现在的core2.2或者3.0里面应该是存在appsettings.json)
using System;using System.Collections.Generic;using System.Linq;using System.Threading.Tasks;namespace OptionsBindSample{ public class Class { public int ClassNo { get; set; } public string ClassDesc { get; set; } public ListStudents { get; set; } } public class Students { public string Name { get; set; } public string Age { get; set; } }}
{ "ClassNo": "1", "ClassDesc": "AspNetCore", "Students": [ { "name": "Tom", "age": "8" }, { "name": "jerry", "age": "7" }, { "name": "rose", "age": "18" } ]}
我们在Startup 中添加一个 IConfiguration,然后再构造函数中注入:
public class Startup { public IConfiguration Configurations { get; set; } public Startup(IConfiguration configuration) { this.Configurations = configuration; }
接下来,我们读取配置文件中的内容;
public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } app.Run(async (context) => { var myClass = new Class(); Configurations.Bind(myClass); await context.Response.WriteAsync($"ClassNo:{myClass.ClassNo}"); await context.Response.WriteAsync($"ClassDesc:{myClass.ClassDesc}"); await context.Response.WriteAsync($"{myClass.Students.Count}"); }); }
最后启动我们使用core的控制台应用启动即可;
好的,现在接下来将配置文件读取到MVC的视图中去。首先添加一个Home控制器,在控制器中注入Class,
修改代码如下:
public class HomeController : Controller { private readonly Class _myClass; public HomeController(IOptionsoptionsClass) { this._myClass = optionsClass.Value; } public IActionResult Index() { return View(_myClass); } }
修改我们的startup.cs 和添加Index.cshtml,将视图的model设置为Class;
using System;using System.Collections.Generic;using System.Linq;using System.Threading.Tasks;using Microsoft.AspNetCore.Builder;using Microsoft.AspNetCore.Hosting;using Microsoft.AspNetCore.Http;using Microsoft.Extensions.Configuration;using Microsoft.Extensions.DependencyInjection;namespace OptionsBindSample{ public class Startup { public IConfiguration Configurations { get; set; } public Startup(IConfiguration configuration) { this.Configurations = configuration; } // This method gets called by the runtime. Use this method to add services to the container. // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940 public void ConfigureServices(IServiceCollection services) { services.Configure(Configurations); //添加MVC,依赖注入配置加到里面; services.AddMvc(); } // This method gets called by the runtime. Use this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } app.UseMvcWithDefaultRoute();//使用默认路由 } }}
@model MVCConfigApplication.Class@{ ViewData["Title"] = "Index";}Index
Class.No:@Model.ClassNo
Class.Desc:@Model.ClassDesc
Students:
@foreach (var itemStudent in Model.Students) { @itemStudent.Name @itemStudent.Age }
当然,我们也可以不使用控制器,在视图中直接注入MyClass。我们在HomeController中删除依赖注入的代码,修改Index.cshtml代码如下
public class HomeController : Controller { public IActionResult Index() { return View(); } }@using Microsoft.Extensions.Options@inject IOptionsClassAccesser;@{ViewData["Title"] = "Index";} index
Class.No:@ClassAccesser.Value.ClassNo
Class.Desc:@ClassAccesser.Value.ClassDesc
Students:
@foreach (var itemStudent in ClassAccesser.Value.Students) { Name:@itemStudent.Name Age:@itemStudent.Age }
配置文件热更新
将IOptions 改为IOptionsSnapshot:
在asp.net core 中,WebHost.CreateDefaultBuilder(args) 方法中,默认加载appsettings.json文件,并且将是否更改重新加载设置为true;
F12进去阅读下源代码,可以看到这三个参数;或者去GitHub上面可查看Core的源代码;
这里是github webhost.cs源码:
所以我们想关闭热更新只需要将WebHost的ConfigureAppConfiguration方法中 config.AddJsonFile第三个参数设置为false就可以了。 config.AddJsonFile("appsettings.json", false, false);
总结
在框架配置中,有两个最重要的对象。第一个是IConfigurationSource,第二个是IConfigurationProvider。IConfigurationSource 在实例化 ConfigurationBuilder时候,可以把不同的Source添加至builder,例如Program中的BuildWebHost方法,最后使用生成器模式统一生成(Build),追加到IConfigurationProvider当中。读取时候,就根据IConfigurationProvider当中是否存在"Key",把对应的值读取出来;