ASP.NET Core 2.2 基础知识(五) 环境

一.环境变量

系统启动时,会读取环境变量 ASPNETCORE_ENVIRONMENT ,并将该变量的值存储在 IHostingEnvironment.EnvironmentName 字段中.如:

新建一个 WebAPI 项目,修改 Configure 方法:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
......
{
app.Run(async context =>
{
context.Response.ContentType = "text/plain;charset=utf-8";//没有这句话,中文会出现乱码.
await context.Response.WriteAsync($"当前环境 : {env.EnvironmentName}");
});
}
......
}

ASPNETCORE_ENVIRONMENT 可以设置为任意值,但是 ASP.NET Core 框架只支持 3 个值:

Development 

Staging

Production

如果没有设置该变量的值,则默认 Production

那么问题来了,在哪里设置呢?

方法一 : launchSettings.json

打开上例创建的 WebAPI 项目的 launchSettings.json 文件:

{
"$schema": "http://json.schemastore.org/launchsettings.json",
"iisSettings": {
"windowsAuthentication": false,
"anonymousAuthentication": true,
"iisExpress": {
"applicationUrl": "http://localhost:53476",
"sslPort": 44307
}
},
"profiles": {
//部署到IIS时,会读取该节点的设置.
"IIS Express": {
"commandName": "IISExpress",
"launchBrowser": true,
"launchUrl": "api/values",
"environmentVariables": {
//"ASPNETCORE_ENVIRONMENT": "Development"
"ASPNETCORE_ENVIRONMENT": "Production" //我们修改为 "Production" 看效果
}
},
//在控制台启动时,会读取该节点的设置
"EnvironmentDemo1": {
"commandName": "Project",
"launchBrowser": true,
"launchUrl": "api/values",
"applicationUrl": "https://localhost:5001;http://localhost:5000",
"environmentVariables": {
"ASPNETCORE_ENVIRONMENT": "Staging" //我们修改为 "Staging" 看效果
}
}
}
}

IIS下运行效果:

控制台运行效果:

 二.基于环境的 Startup 类

当 ASP.NET Core 应用启动时,会在 Program 类中通过 Startup 类启动应用.

ASP.NET Core 提供了基于不同环境选择不同的 Startup 类的方法.但是类名有个约定,只能这样命名:

Startup{EnvironmentName}

EnvironmentName 为当前环境.

示例:

/// <summary>
/// 开发环境启动类
/// </summary>
public class StartupDevelopment
{
public void ConfigureServices(IServiceCollection services){}

public void Configure(IApplicationBuilder app, IHostingEnvironment env){}
}

/// <summary>
/// 模拟环境启动类
/// </summary>
public class StartupStaging
{
public void ConfigureServices(IServiceCollection services){}

public void Configure(IApplicationBuilder app, IHostingEnvironment env){}
}

/// <summary>
/// 生产环境启动类
/// </summary>
public class StartupProduction
{
public void ConfigureServices(IServiceCollection services){}

public void Configure(IApplicationBuilder app, IHostingEnvironment env){}
}

要让系统根据当前环境选择上述3个启动类中的一个,还需要修改调用方法.

默认的调用方法是这样的:

public class Program
{
public static void Main(string[] args)
{
CreateWebHostBuilder(args).Build().Run();
}

public static IWebHostBuilder CreateWebHostBuilder(string[] args) => WebHost.CreateDefaultBuilder(args).UseStartup<Startup>();
}

需要修改成:

public static IWebHostBuilder CreateWebHostBuilder(string[] args)
{
var assemblyName = typeof(Startup).GetTypeInfo().Assembly.FullName;
return WebHost.CreateDefaultBuilder(args).UseStartup(assemblyName);
}

 二.基于环境的 ConfigureServices 方法和 Configure 方法

上代码一目了然:

public void ConfigureStaging(IApplicationBuilder app, IHostingEnvironment env)
{

}

public void ConfigureStagingServices(IServiceCollection services)
{

}