Xamarin -令牌到期时注销

Question

我有一个托管在Azure上的Api，我在我的Xamarin Forms项目中使用。

我在开始时显示登录页面，我检查JWT令牌是否已经过期，但我也想检查每个http方法，以防它在用户使用应用程序时过期。

所以我需要向用户显示登录页面并告诉他们再次登录，我一直在寻找如何做到这一点，我不能得到正确的

这是我的AzureApiService类。

public class AzureApiService
{
HttpClient httpClient;
public AzureApiService()
{
#if DEBUG
var httpHandler = new HttpClientHandler
{
ServerCertificateCustomValidationCallback = (o, cert, chain, errors) => true
};
#else
var httpHandler = new HttpClientHandler();
#endif
httpClient = new HttpClient(httpHandler);
httpClient.Timeout = TimeSpan.FromSeconds(15);
httpClient.MaxResponseContentBufferSize = 256000;
}
public async Task<string> LoginAsync(string url, AuthUser data)
{
var user = await HttpLoginPostAsync(url, data);
if (user != null)
{
//Save data on constants
CurrentPropertiesService.SaveUser(user);
return user.Token;
}
else
{
return string.Empty;
}
}
// Generic Get Method
public async Task<T> HttpGetAsync<T>(string url, string token)
{
T result = default(T);
try
{
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
HttpResponseMessage response = httpClient.GetAsync(url).Result;
HttpContent content = response.Content;
if (response.IsSuccessStatusCode)
{
var jsonResponse = await content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
}
else
{
if (IsExpired(token))
{
await Logout();
}
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);
}
}
catch (Exception ex)
{
OnError(ex.ToString());
}
return result;
}
// Generic Post Method
public async Task<T> HttpPostAsync<T>(string url, string token, T data)
{
T result = default(T); // résultat de type générique
try
{
string json = JsonConvert.SerializeObject(data);
StringContent content = new StringContent(json, Encoding.UTF8, "application/json");
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var response = await httpClient.PostAsync(new Uri(url), content);
var jsonResponse = await response.Content.ReadAsStringAsync();
if (response.IsSuccessStatusCode)
{
var jsons = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
}
else
{
if (IsExpired(token))
{
await Logout();
}
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);
}
return result;
}
catch (Exception ex)
{
OnError(ex.ToString());
return result;
}
}
// Generic Put Method
public async Task<T> HttpPutAsync<T>(string url, string token, T data)
{
T result = default(T); // résultat de type générique
try
{
string json = JsonConvert.SerializeObject(data);
StringContent content = new StringContent(json, Encoding.UTF8, "application/json");
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var response = await httpClient.PutAsync(new Uri(url), content);
if (response.IsSuccessStatusCode)
{
var jsonResponse = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
}
else
{
if (IsExpired(token))
{
await Logout();
}
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);
}
return result;
}
catch (Exception ex)
{
OnError(ex.ToString());
return result;
}
}
// Generic Delete Method
public async Task<bool> HttpDeleteAsync(string url, string token)
{
try
{
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var response = await httpClient.DeleteAsync(url);
if (response.IsSuccessStatusCode)
{
return true;
}
else
{
if (IsExpired(token))
{
await Logout();
}
return false;
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);
}
}
catch (Exception ex)
{
OnError(ex.ToString());
return false;
}
}
// Login Post Method
public async Task<T> HttpLoginPostAsync<T>(string url, T data)
{
T result = default(T); // résultat de type générique
try
{
string json = JsonConvert.SerializeObject(data);
StringContent content = new StringContent(json, Encoding.UTF8, "application/json");
var response = await httpClient.PostAsync(new Uri(url), content);
if (response.IsSuccessStatusCode)
{
var jsonResponse = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
}
else
{
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);
}
return result;
}
catch (Exception ex)
{
OnError(ex.ToString());
return result;
}
}
public bool IsExpired(string token)
{
if (token == null || "".Equals(token))
{
return true;
}
/***
* Make string valid for FromBase64String
* FromBase64String cannot accept '.' characters and only accepts stringth whose length is a multitude of 4
* If the string doesn't have the correct length trailing padding '=' characters should be added.
*/
int indexOfFirstPoint = token.IndexOf('.') + 1;
String toDecode = token.Substring(indexOfFirstPoint, token.LastIndexOf('.') - indexOfFirstPoint);
while (toDecode.Length % 4 != 0)
{
toDecode += '=';
}
//Decode the string
string decodedString = Encoding.ASCII.GetString(Convert.FromBase64String(toDecode));
//Get the "exp" part of the string
Regex regex = new Regex("("exp":)([0-9]{1,})");
Match match = regex.Match(decodedString);
long timestamp = Convert.ToInt64(match.Groups[2].Value);
DateTime date = new DateTime(1970, 1, 1).AddSeconds(timestamp);
DateTime compareTo = DateTime.UtcNow;
int result = DateTime.Compare(date, compareTo);
return result < 0;
}
private async Task Logout()
{
CurrentPropertiesService.Logout();
CurrentPropertiesService.RemoveCart();
await Shell.Current.GoToAsync($"//main");
}
private void OnError(string error)
{
Console.WriteLine("[WEBSERVICE ERROR] " + error);
}
}

所以你可以看到，在每个http方法中，我试图检查令牌是否已经过期，然后注销，但它只是给出一个错误。

在我的Logout方法，我只是想删除所有的属性，然后导航到登录页面，但它不工作。

请帮助我想知道如何做到这一点。谢谢。

编辑

尝试实现DelegatingHandler停止在SendAsync

这是我的HttpDelegatingHandler类

public class HttpDelegatingHandler : DelegatingHandler
{
public HttpDelegatingHandler(HttpMessageHandler innerHandler) : base(innerHandler)
{
}
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
request.Headers.Add("Bearer", CurrentPropertiesService.GetToken()); 
// before request
HttpResponseMessage response = await base.SendAsync(request, cancellationToken);
// after request
if (response.StatusCode == System.Net.HttpStatusCode.Unauthorized)
{
await Logout();
}
return response;
}
private async Task Logout()
{
CurrentPropertiesService.Logout();
CurrentPropertiesService.RemoveCart();
await Shell.Current.GoToAsync($"//main");
}
}

这里是我的AzureApiService类

public class AzureApiService
{
HttpClient httpClient;
public AzureApiService()
{
var clientHandler = new HttpClientHandler();
#if DEBUG
clientHandler.ServerCertificateCustomValidationCallback =
(sender, cert, chain, sslPolicyErrors) =>
{
return true;
};
#endif
httpClient = new HttpClient(new HttpDelegatingHandler(clientHandler));
httpClient.Timeout = TimeSpan.FromSeconds(15);
httpClient.MaxResponseContentBufferSize = 256000;
}
public async Task<string> LoginAsync(string url, AuthUser data)
{
var user = await HttpLoginPostAsync(url, data);
if (user != null)
{
//Save data on constants
CurrentPropertiesService.SaveUser(user);
return user.Token;
}
else
{
return string.Empty;
}
}
// Generic Get Method
public async Task<T> HttpGetAsync<T>(string url, string token)
{
T result = default(T);
try
{
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
var response = await httpClient.GetAsync(url);
HttpContent content = response.Content;

var jsonResponse = await content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
throw new Exception(((int)response.StatusCode).ToString() + " - " + response.ReasonPhrase);

}
catch (Exception ex)
{
OnError(ex.ToString());
}
return result;
}

PostAsync

// Login Post Method
public async Task<T> HttpLoginPostAsync<T>(string url, T data)
{
T result = default(T); // résultat de type générique
try
{
string json = JsonConvert.SerializeObject(data);
StringContent content = new StringContent(json, Encoding.UTF8, "application/json");
var response = await httpClient.PostAsync(new Uri(url), content);

var jsonResponse = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);

return result;
}
catch (Exception ex)
{
OnError(ex.ToString());
return result;
}
}

但是就像我说的，当试图获取数据时它会停止

Answer 1

您可以在自定义委派处理程序中处理401未经授权的响应。这样你就可以在一个地方处理请求执行前后的任何事情。

public class HttpDelegatingHandler : DelegatingHandler
{
public HttpDelegatingHandler(HttpMessageHandler innerHandler) : base(innerHandler)
{
}
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
request.Headers.Add("Authorization", string.Format("Basic {0}", MyUserRepository.AuthToken));
// before request
HttpResponseMessage response = await base.SendAsync(request, cancellationToken);
// after request
if (response.StatusCode == System.Net.HttpStatusCode.Unauthorized)
{
await Shell.Current.GoToAsync($"//main");
}
return response;
}
}
public class AzureApiService
{
HttpClient httpClient;
public AzureApiService()
{
var clientHandler = new HttpClientHandler();
#if DEBUG
clientHandler.ServerCertificateCustomValidationCallback =
(sender, cert, chain, sslPolicyErrors) =>
{
return true;
};
#endif
httpClient = new HttpClient(new HttpDelegatingHandler(clientHandler));
httpClient.Timeout = TimeSpan.FromSeconds(15);
httpClient.MaxResponseContentBufferSize = 256000;
}
....
// Generic Get Method
public async Task<T> HttpGetAsync<T>(string url, string token)
{
T result = default(T);
try
{
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
HttpResponseMessage response = await httpClient.GetAsync(url);

var jsonResponse = await response.Content.ReadAsStringAsync();
result = JsonConvert.DeserializeObject<T>(jsonResponse);
}
catch (Exception ex)
{
OnError(ex.ToString());
}
return result;
}