.Net Core3.0 配置Configuration的实现

准备

.NET core和.NET项目配置上有了很大的改变,支持的也更加丰富了比如命令行,环境变量,内存中.NET对象,设置文件等等。.NET项目我们常常把配置信息放到webConfig 或者appConfig中。配置相关的源码https://github.com/aspnet/Extensions;如果打开源码项目如果遇到以下错误,未遇到直接跳过。

.Net Core3.0 配置Configuration的实现_第1张图片

错误提示:error : The project file cannot be opened by the project system, because it is missing some critical imports or the referenced SDK cannot be found. Detailed Information:

解决办法:查看本地安装的sdk 与 global.json中制定的版本是否一致:然后修改即可

.Net Core3.0 配置Configuration的实现_第2张图片

开始

新建个Asp.net Core web应用程序系统默认创建了appsettings.json ;在应用启动生成主机时调用CreateDefaultBuilder方法,默认会加载appsettings.json。代码如下:

public static IHostBuilder CreateDefaultBuilder(string[] args)
    {
      var builder = new HostBuilder();
​
      builder.UseContentRoot(Directory.GetCurrentDirectory());
      builder.ConfigureHostConfiguration(config =>
      {
        config.AddEnvironmentVariables(prefix: "DOTNET_");
        if (args != null)
        {
          config.AddCommandLine(args);
        }
      });
​
      builder.ConfigureAppConfiguration((hostingContext, config) =>
      {
        var env = hostingContext.HostingEnvironment;
​
        config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
           .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
​
        if (env.IsDevelopment() && !string.IsNullOrEmpty(env.ApplicationName))
        {
          var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
          if (appAssembly != null)
          {
            config.AddUserSecrets(appAssembly, optional: true);
          }
        }

利用GetValue,GetSection,GetChildren读取appsettings.json 键值对 。我们打开appsettings.json文件:

.Net Core3.0 配置Configuration的实现_第3张图片

将文件读入配置时,会创建一下唯一的分层健来保存配置值:

  • Logging:LogLevel:Default
  • Logging:LogLevel:System
  • Logging:LogLevel:Microsoft
  • Logging:LogLevel:Microsoft.Hosting.Lifetime
  • AllowedHosts
var jsonValue = $"AllowedHosts:{_config["AllowedHosts"]}"+ "\r\n";
      jsonValue += "Logging:LogLevel:Default:" + _config.GetValue("Logging:LogLevel:Default")+ "\r\n";
​
      //GetSection 返回IConfigurationSection;如果未匹配到 返回null
      //jsonValue += "---" + _config.GetSection("Logging:LogLevel:System");
      jsonValue += "Logging:LogLevel:System:" + _config.GetSection("Logging:LogLevel:System").Value+ "\r\n\n";
     
      var logSection = _config.GetSection("Logging:LogLevel");
      var configurationSections = logSection.GetChildren();
      foreach (var sections in configurationSections) 
      {
        jsonValue += $"{sections.Path}:{sections.Value}";
        jsonValue += "\r\n";
      }
      jsonValue += "\r\n";

.Net Core3.0 配置Configuration的实现_第4张图片

配置指定json文件绑定至类

新建一个json文件-AAAppSettings.json

{
 "AA": {
  "RabbitMqHostUrl": "rabbitmq://localhost:5672",
  "RabbitMqHostName": "localhost",
  "RabbitMqUserName": "admin",
  "RabbitMqPassword": "123"
 }
}

使用ConfigureAppConfiguration方法配置指定的json文件

public static IHostBuilder CreateHostBuilder(string[] args) =>
      Host.CreateDefaultBuilder(args)
      .ConfigureAppConfiguration((hostingContext, config) =>
      {
        config.SetBasePath(Directory.GetCurrentDirectory());
        config.AddJsonFile("AAAppSettings.json", optional: true, reloadOnChange: true);
      })

使用bind方法绑定到新建的类上如:

public partial class AAConfig
  {
    public string RabbitMqHostUrl { get; set; }
    public string RabbitMqHostName { get; set; }
    public string RabbitMqUserName { get; set; }
    public string RabbitMqPassword { get; set; }
  }
var aaConfig = new AAConfig();
_config.GetSection("AA").Bind(aaConfig);
jsonValue += aaConfig.RabbitMqHostUrl + "\r\n";
jsonValue += aaConfig.RabbitMqHostName + "\r\n";
jsonValue += aaConfig.RabbitMqUserName + "\r\n";
jsonValue += aaConfig.RabbitMqPassword + "\r\n";
return jsonValue;

运行输出:

.Net Core3.0 配置Configuration的实现_第5张图片

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