AOP中的NAutowired

Question

我的目标是将HttpContextAccessor注入我的记录器，因为我使用Metalama。伐木部分没问题，还能用。但是现在我想让我的代码更简洁，以后更通用。为此，我需要访问HttpContextAccessor。因为我不能在Metalama OverrideMethodAspect派生类中使用DI，所以我找到了一个很好的库，它允许我使用字段注入器注入值。在示例应用程序中，即使我将代码拆分到Service和Repository层，它也可以正常工作。我可以访问HttpContextAccessor。但在我的项目中，我无法获得注入到我的属性中的HttpContextAccessor实例。它总是空的。我的想法是封装类中需要的接口，使用NAutowired字段注入器注入所需的类，然后在OverrideMethodAspect重写方法中使用类的实例。

[Service]
public class ServiceFactory
{
    [Autowired(typeof(HttpContextAccessor))]
    public IHttpContextAccessor HttpContextAccessor { get; set; }
}

public class LoggingAttribute : OverrideMethodAspect
{
    public override dynamic OverrideMethod()
    {
        try
        {
            var serviceFactory = new ServiceFactory();
            var result = meta.Proceed();

            
            var user = (serviceFactory.HttpContextAccessor.HttpContext.User.Identity as ClaimsIdentity).Claims.FirstOrDefault(x => x.Type == "uid");
            var loggedInUserIdentity = !string.IsNullOrEmpty(user?.Value) ?
                                       $" => by user: {user.Value}" :
                                       string.Empty;
        }
    }
}

问题是，HttpContextAccessor在serviceFactory中总是为空。我将启动类更改为，如示例所示。

var builder = WebApplication.CreateBuilder(args);
builder.WebHost.UseSerilog();
builder.Services.AddControllers()
    .AddControllersAsServices();

builder.Services.Replace(ServiceDescriptor.Transient<IControllerActivator, NAutowiredControllerActivator>());
var assemblies = new List<string>
{
    "aaa.Web.Api",
    "aaa.Core",
    "aaa.Comon"
};
builder.Services.AutoRegisterDependency(assemblies);

Answer 1

对于.NET 6及以后，

创建ServiceTool类，

public static class ServiceTool
{
        public static IServiceProvider ServiceProvider { get; private set; }

        public static IServiceCollection Create(IServiceCollection services)
        {
            ServiceProvider = services.BuildServiceProvider();
            return services;
        }
}

在program.cs管道中创建注册服务工具的扩展，

public static class ServiceCollectionExtensions
    {
        public static IServiceCollection AddDependencyResolvers(this IServiceCollection services)
        {
            services.AddSingleton<IHttpContextAccessor,HttpContextAccessor>();
            return ServiceTool.Create(services);
        }
    }

之后，您必须在program.cs中注册它

builder.Services.AddDependencyResolvers();

在这些步骤之后，您可以在应用程序中的任何地方访问HttpContextAccessor对象；

var httpContextAccessor = ServiceTool.ServiceProvider.GetService<IHttpContextAccessor>();

Answer 2

关键是：

   var serviceFactory = new ServiceFactory();

如果希望通过依赖项注入ServiceFactory类的实例，那么ServiceFactory本身也应该通过依赖注入实例，如果使用new创建实例，则容器将无法工作。应该在ServiceFactory中注入LoggingAttribute实例

[Service]
public class LoggingAttribute : OverrideMethodAspect
{
    [Autowired]
    public ServiceFactory serviceFactory;
    public override dynamic OverrideMethod()
    {
        try
        {
            var result = meta.Proceed();

            
            var user = (serviceFactory.HttpContextAccessor.HttpContext.User.Identity as ClaimsIdentity).Claims.FirstOrDefault(x => x.Type == "uid");
            var loggedInUserIdentity = !string.IsNullOrEmpty(user?.Value) ?
                                       $" => by user: {user.Value}" :
                                       string.Empty;
        }
    }
}

最后，还应该以同样的方式将LoggingAttribute实例注入控制器。