通过SQL Server依赖注入刷新ASP.NET Core中的Azure Active Directory访问令牌

Question

我有一个ASP.NET Core网站（带有Razor页面），该网站使用带有Entity Framework Core的Azure SQL数据库。 我在Startup.cs中创建数据库上下文以进行依赖项注入。 棘手的部分是，我正在对来自我的App Service中具有托管身份的数据库使用Azure Active Directory身份验证。 所以我的连接字符串中没有任何凭证，看起来像这样：

"DatabaseConnectionString": "Server=tcp:myserver.database.windows.net,1433;Initial Catalog=mydb;Persist Security Info=False;MultipleActiveResultSets=True;Encrypt=True;TrustServerCertificate=False;Connection Timeout=30;"

在Startup.cs中，我使用托管身份获取访问令牌：

public void ConfigureServices(IServiceCollection services)
{
    // other stuff...

    var dbConnection = new SqlConnection(Configuration["DatabaseConnectionString"])
    {
        AccessToken = new AzureServiceTokenProvider().GetAccessTokenAsync("https://database.windows.net/").Result
    };
    services.AddDbContext<AlpinehutsDbContext>(options => options.UseSqlServer(dbConnection));
}

这一切都像一个魅力。 但是，过了一段时间（我不确定确切要到多长时间）之后，令牌似乎已过期，然后出现以下错误，并且直到重新启动整个应用程序服务，数据库连接才不再起作用：

2019-07-30 08:31:25.635 +00:00 [Information] Microsoft.AspNetCore.Mvc.RazorPages.Internal.PageActionInvoker: Executing handler method AlpinHutsDashboard.Pages.HutsModel.OnGetAsync - ModelState is Valid
2019-07-30 08:31:25.635 +00:00 [Information] Microsoft.EntityFrameworkCore.Infrastructure: Entity Framework Core 2.2.6-servicing-10079 initialized 'AlpinehutsDbContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: None
2019-07-30 08:31:25.861 +00:00 [Error] Microsoft.EntityFrameworkCore.Database.Connection: An error occurred using the connection to database 'mydb' on server 'tcp:myserver.database.windows.net,1433'.System.Data.SqlClient.SqlException (0x80131904): Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'.at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken)at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)at System.Data.ProviderBase.DbConnectionPool.WaitForPendingOpen()--- End of stack trace from previous location where exception was thrown ---at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnectionAsync(Boolean errorsExpected, CancellationToken cancellationToken)ClientConnectionId:17e2a3f3-9dba-4c30-baff-5fa9e5e082c6Error Number:18456,State:1,Class:14ClientConnectionId before routing:7dc72f29-efa2-420d-8f28-8d63de1c059cRouting Destination:f0ae6a8cac94.tr5.westeurope1-a.worker.database.windows.net,11017

所以我的问题是：当我最初仅在启动时获得令牌时，如何刷新令牌？

Answer 1

对于您的问题，这是由于您将dbConnection传递给AlpinehutsDbContext 。 初始化AlpinehutsDbContext ，它将始终使用dbConnection 。 然后，如果连接无效，它将引发错误。

您可以在初始化AlpinehutsDbContext时尝试初始化dbConnection ，例如

services.AddDbContext<AlpinehutsDbContext>(options =>
{
    var dbConnection = new SqlConnection(Configuration["DatabaseConnectionString"])
    {
        AccessToken = new AzureServiceTokenProvider().GetAccessTokenAsync("https://database.windows.net/").Result
    };
    options.UseSqlServer(dbConnection);
});

这样，它将在初始化AlpinehutsDbContext时检索neweast令牌。