我会用某种BaseApiService 来处理这个问题
public class BaseApiService
{
private readonly IHttpClientFactory httpClientFactory;
private readonly ITokenHandler tokenHandler;
public BaseApiService(IHttpClientFactory httpClientFactory, ITokenHandler tokenHandler)
{
this.httpClientFactory = httpClientFactory;
this.tokenHandler = tokenHandler;
}
protected async Task<HttpResponseMessage> RequestAsync(HttpRequestMessage requestMessage)
{
var httpClient = httpClientFactory.CreateClient();
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", tokenHandler.Token);
var response = await httpClient.SendAsync(requestMessage);
if (!response.IsSuccessStatusCode)
{
if (response.StatusCode == HttpStatusCode.Unauthorized)
{
var token = await tokenHandler.UpdateTokenAsync();
requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
return await RequestAsync(requestMessage);
}
}
return response;
}
}
它将负责发出请求、响应序列化（注意，为了简单起见，我使用了字符串响应）和处理每个请求的令牌。此外，您可能需要考虑处理错误并处理无限循环，因为它当前正在调用 self（例如，在第二次调用时，如果再次未经授权，则退出并出错）。
令牌处理程序将在 DI 中定义为单例，这是实现
public interface ITokenHandler
{
string Token { get; }
Task<string> UpdateTokenAsync();
}
public class TokenHandler : ITokenHandler
{
private readonly IHttpClientFactory httpClientFactory;
public string Token { get; private set; }
public TokenHandler(IHttpClientFactory httpClientFactory)
{
this.httpClientFactory = httpClientFactory;
}
public async Task<string> UpdateTokenAsync()
{
var httpClient = httpClientFactory.CreateClient();
var result = await httpClient.PostAsync("/external-api/token", new FormUrlEncodedContent(new []
{
new KeyValuePair<string, string>("username", "external-admin"),
new KeyValuePair<string, string>("password", "external-password"),
}));
// or handle it however you want
var token = result.IsSuccessStatusCode
? await result.Content.ReadAsStringAsync()
: null;
if (!String.IsNullOrEmpty(token))
{
Token = token;
}
return Token;
}
}
这就是你使用BaseApiService的方式
public class TodoService : BaseApiService
{
public TodoService(IHttpClientFactory httpClientFactory, ITokenHandler tokenHandler)
: base(httpClientFactory, tokenHandler)
{
}
public async Task<string> GetTodoAsync(int id)
{
var response = await RequestAsync(new HttpRequestMessage(HttpMethod.Get, $"/todo/{id}"));
return await response.Content.ReadAsStringAsync();
}
}
我认为您不需要添加任何 ValidTo 逻辑，而只需依赖来自 3rd 方 API 的 Unauthorized 响应，因为您只会使代码复杂化并且您必须处理 Unauthorized无论如何都要回复。
唯一的问题是您可以通过lock 从TokenHandler 获取/设置令牌，但这只是一个基本示例，展示了我将如何实现它的想法。