c# - 如何在 DI 设置期间自动验证 appSettings.json 文件中的配置值？

Question

我在 .NET Core 项目的 appSettings.json 文件中添加了配置。为了简单起见，我以数据库设置为例。所以在设置文件中你会有

{
  "Database": {
    "Host": "localhost",
    "Port": 1234,
    "Database": "myDb",
    "Username": "username",
    "Password": "pw",
    "EnablePooling": true
  }
}

在 Startup.cs 文件中配置服务时，我希望通过依赖注入(inject)来访问这些设置。用于此的数据模型是

public class DatabaseSettings
{
    public string Host { get; set; }
    public ushort Port { get; set; }
    public string Database { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public bool EnablePooling { get; set; }
}

我这样配置

private void SetupSettings(IServiceCollection services)
{
    ServiceProvider serviceProvider = services.BuildServiceProvider();
    IConfiguration configuration = serviceProvider.GetService<IConfiguration>();

    IConfigurationSection databaseConfigurationSection = configuration.GetSection("Database");
    services.Configure<DatabaseSettings>(databaseConfigurationSection);
}

最后我想验证这些设置。我知道我可以创建一个验证器类来实现 IValidateOptions界面。

public class DatabaseSettingsValidator : IValidateOptions<DatabaseSettings>
{
    private readonly IList<string> failures;

    public DatabaseSettingsValidator()
    {
        failures = new List<string>();
    }
    
    public ValidateOptionsResult Validate(string databaseSettingsName, DatabaseSettings databaseSettings)
    {
        if (databaseSettings == null)
            failures.Add($"{databaseSettingsName} are required.");
        
        if (string.IsNullOrEmpty(databaseSettings?.Host))
            failures.Add($"{nameof(databaseSettings.Host)} must not be empty.");
        
        if (string.IsNullOrEmpty(databaseSettings?.Database))
            failures.Add($"{nameof(databaseSettings.Database)} must not be empty.");
        
        if (failures.Any())
            return ValidateOptionsResult.Fail(failures);

        return ValidateOptionsResult.Success;
    }
}

但是我必须创建这个类并调用 Validate吗？我自己的方法？也许有类似这个示例代码的东西？
.

services.ValidateConfiguration<IOptions<DatabaseSettings>, DatabaseSettingsValidator>();

因此，您传入配置的设置和要使用的验证器。

Answer 1

but I'm struggling with two questions:

Is there a way I can collect all failures instead of returning afterone? So you would get a list of failures instead of having to fix oneby one.

Do I have to create this class and call the Validate method on my own?Maybe there is something like this sample code?

services.ValidateConfiguration<IOptions,DatabaseSettingsValidator>(); So you pass in the configured settingsand the validator to use.

是的，我们可以收集所有失败列表并立即显示它们，我们还可以创建一个包含 Validate 方法的类。请检查以下步骤:
首先，由于类名是“ DatabaseSettings ”，最好将配置节名称设置为与类名相同:

{
  "DatabaseSettings": {
    "Host": "localhost",
    "Port": 1234,
    "Database": "myDb",
    "Username": "username",
    "Password": "pw",
    "EnablePooling": true
  }
}

[注意] 如果使用不同的名称，该值可能不会映射到数据库设置类，因此在验证数据时，它们都为空。
其次，使用 Data Annotations 方法将验证规则添加到模型属性中。

public class DatabaseSettings
{
    [Required]
    public string Host { get; set; }
    [Required]
    public ushort Port { get; set; }
    [Required]
    public string Database { get; set; }
    [Required]
    public string Username { get; set; }
    [Required]
    public string Password { get; set; }
    [Required]
    public bool EnablePooling { get; set; }
}

第三，创建一个包含 ConfigureAndValidate 方法的 ServiceCollectionExtensions 类:

public static class ServiceCollectionExtensions
{
    public static IServiceCollection ConfigureAndValidate<T>(this IServiceCollection @this,
        IConfiguration config) where T : class
        => @this
            .Configure<T>(config.GetSection(typeof(T).Name))
            .PostConfigure<T>(settings =>
            {
                var configErrors = settings.ValidationErrors().ToArray();
                if (configErrors.Any())
                {
                    var aggrErrors = string.Join(",", configErrors);
                    var count = configErrors.Length;
                    var configType = typeof(T).Name;
                    throw new ApplicationException(
                        $"Found {count} configuration error(s) in {configType}: {aggrErrors}");
                }
            });
}

然后，注册 ConfigureAndValidate 服务:

public void ConfigureServices(IServiceCollection services)
{
    services.ConfigureAndValidate<DatabaseSettings>(Configuration);
}

最后，获取异常列表。

public class HomeController : Controller
{
    private readonly DatabaseSettings_settings;

    public HomeController(IOptions<DatabaseSettings> settings)
    {
        _settings = settings.Value; // <-- FAIL HERE THROW EXCEPTION
    }
}

然后，像这样的测试结果(我从 appSettings.json 中删除了主机和用户名):

更多详细信息，可以查看这篇博客: Validating configuration in ASP.NET Core