HttpContext在构造函数中为null

Question

我有一个的UserContext服务，我就会把一些基本的功能（” IsAuthenticated，GetUser等...）

为此，我需要将HTTPContextWebAPI控制器中的传递给我的类库服务。

实际上，HttpContext始终null在Web api控制器中。

有人有解决我问题的解决方案吗？有没有更好的方法来实现它。

Web API用户控制器

[Route("api/[controller]")]
[Authorize]
public class UserController : Controller
{
    private readonly IUserContextServices _userContextServices;
    private readonly User loggedUser;

    public UserController()
    {
       //HttpContext ALWAYS NULL
        _userContextServices = new UserContextService(HttpContext);
    }
 }  

UserContext服务

namespace MyProj.Services
{
    public interface IUserContextServices
    {
        UserContext GetUserContext();
        bool IsUserAuthenticated();
    }

    public class UserContextService : IUserContextServices
    {
        private readonly HttpContext _context;
        private UserContext _userContext;
        public UserContextService(HttpContext context)
        {
            _context = context;
            InitUserContext();
        }

        private IEnumerable<Claim> GetUserClaims()
        {
            if (IsUserAuthenticated())
            {
                return _context.User.Claims;
            }
            return null;
        }

        private void InitUserContext()
        {
            if (IsUserAuthenticated())
            {
                var claims = GetUserClaims();
                _userContext = new UserContext();
                _userContext.Email = claims.First(p => p.Type == "email").Value;
                _userContext.AspNetUserID = claims.First(p => p.Type == "sub").Value;
            }
        }

        public UserContext GetUserContext()
        {
            return _userContext;
        }

        public bool IsUserAuthenticated()
        {
            return _context.User != null && _context.User.Identity != null && _context.User.Identity.IsAuthenticated;
        }
    }
}

Answer 1

HttpContext调用Controller的构造函数时不可用。您将不得不重新设计代码，以便稍后在调用流程中获取上下文。这就是IHttpContextAccessor它的用途。

public interface IHttpContextAccessor {
    HttpContext HttpContext { get; }
}

将其注入服务中，然后根据需要稍后访问上下文。

public class UserContextService : IUserContextServices {
    private readonly IHttpContextAccessor contextAccessor;
    private UserContext _userContext;
    public UserContextService(IHttpContextAccessor accessor) {
        contextAccessor = accessor;
    }

    private HttpContext Context {
        get {
            return contextAccessor.HttpContext;
        }
    }

    public UserContext GetUserContext() {
        if (_userContext == null && IsUserAuthenticated()) {
            var claims = Context?.User?.Claims;
            _userContext = new UserContext() {
                Email = claims.First(p => p.Type == "email").Value,
                AspNetUserID = claims.First(p => p.Type == "sub").Value
            };
        }
        return _userContext;
    }

    public bool IsUserAuthenticated() {
        return Context?.User?.Identity?.IsAuthenticated;
    }
}

将服务抽象注入控制器

[Route("api/[controller]")]
[Authorize]
public class UserController : Controller {
    private readonly IUserContextServices _userContextServices;
    private readonly User loggedUser;

    public UserController(IUserContextServices userContextServices) {
        _userContextServices = userContextServices;
    }

    //...
}

IHttpContextAccessor默认情况下不在服务集合中，因此您需要Startup.ConfigureServices手动添加它才能注入它：

services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
services.AddTransient<IUserContextServices, UserContextService>();