Custom HttpClient Wrapper

Question

I need to wrap httpClient because I'm using a custom token provider. I will use this code with asp.net mvc to communicate with our webApi2 server. ( Using webApi2 with directly from ui with angularjs etc. off the case. )

I shared this code and asking your opinions because;

• I don't want any deadlock to occur.
• I see code reuse which is bad (but don't know how to solve).
• Maybe throwing exceptions somehow different and correct way.
• It supposed to work under huge load (150K realtime requests from users)

Note: I implemented it with concerns of di. So I can wrap restSharp too.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using MyLibrary.Core.Components.Json;
using MyLibrary.Core.Components.Json.Implementations;
namespace MyLibrary.HttpClientWrapper
{
 public class ResourceServerRestClient : IResourceServerRestClient
 {
 private readonly ITokenProvider _tokenProvider;
 private readonly IJsonManager _jsonManager;
 public ResourceServerRestClient(ITokenProvider tokenProvider, IJsonManager jsonManager)
 {
 _tokenProvider = tokenProvider;
 _jsonManager = jsonManager;
 }
 public string BaseAddress { get; set; }
 public Task<T> GetAsync<T>(string uri, string clientId)
 {
 return CheckAndInvokeAsync(async token =>
 {
 using (var client = new HttpClient())
 { 
 ConfigurateHttpClient(client, token, clientId);
 HttpResponseMessage response = await client.GetAsync(uri).ConfigureAwait(false);
 if (response.IsSuccessStatusCode)
 {
 return await response.Content.ReadAsAsync<T>();
 }
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 });
 }
 public Task<T> PostAsJsonAsync<T>(object data, string uri, string clientId)
 {
 return CheckAndInvokeAsync(async token =>
 {
 using (var client = new HttpClient())
 {
 ConfigurateHttpClient(client, token, clientId);
 HttpResponseMessage response = await client.PostAsJsonAsync(uri, data);
 if (response.IsSuccessStatusCode)
 {
 return await response.Content.ReadAsAsync<T>();
 }
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 });
 }
 public async Task PostAsJsonAsync(object data, string uri, string clientId)
 {
 await CheckAndInvokeAsync(async token =>
 {
 using (var client = new HttpClient())
 {
 ConfigurateHttpClient(client, token, clientId);
 HttpResponseMessage response = await client.PostAsJsonAsync(uri, data);
 if (!response.IsSuccessStatusCode)
 {
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 }
 return Task.FromResult(0);
 });
 }
 public Task PutAsJsonAsync(object data, string uri, string clientId)
 {
 return CheckAndInvokeAsync(async token =>
 {
 using (var client = new HttpClient())
 {
 ConfigurateHttpClient(client, token, clientId);
 HttpResponseMessage response = await client.PutAsJsonAsync(uri, data);
 if (!response.IsSuccessStatusCode)
 {
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 }
 return Task.FromResult(0);
 });
 }
 public Task<T> PutAsJsonAsync<T>(object data, string uri, string clientId)
 {
 return CheckAndInvokeAsync(async token =>
 {
 using (var client = new HttpClient())
 {
 ConfigurateHttpClient(client, token, clientId);
 HttpResponseMessage response = await client.PutAsJsonAsync(uri, data);
 if (response.IsSuccessStatusCode)
 {
 return await response.Content.ReadAsAsync<T>();
 }
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 });
 }
 private void ConfigurateHttpClient(HttpClient client, string bearerToken, string resourceServiceClientName)
 {
 if (!string.IsNullOrEmpty(resourceServiceClientName))
 {
 client.DefaultRequestHeaders.Add("CN", resourceServiceClientName);
 }
 if (string.IsNullOrEmpty(BaseAddress))
 {
 throw new Exception("BaseAddress is required!");
 }
 client.BaseAddress = new Uri(BaseAddress);
 client.Timeout = new TimeSpan(0, 0, 0, 10);
 client.DefaultRequestHeaders.Accept.Clear();
 client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", bearerToken);
 }
 private async Task<T> CheckAndInvokeAsync<T>(Func<string, Task<T>> method)
 {
 try
 {
 string token = await _tokenProvider.IsTokenNullOrExpired();
 if (!string.IsNullOrEmpty(token))
 {
 return await method(token);
 }
 var exception = new Exception();
 exception.Data.Add("StatusCode", HttpStatusCode.Unauthorized);
 throw exception;
 }
 catch (Exception ex)
 {
 if (ex.Data.Contains("StatusCode") && ((HttpStatusCode)ex.Data["StatusCode"]) == HttpStatusCode.Unauthorized)
 {
 string token = await _tokenProvider.GetTokenAsync();
 if (!string.IsNullOrEmpty(token))
 {
 return await method(token);
 }
 }
 throw;
 }
 }
 public void ThrowResourceServerException(List<string> messages)
 {
 string message = messages.Aggregate((p, q) => q + " - " + p);
 var exception = new Exception(message);
 exception.Data.Add("ServiceOperationException", message);
 throw exception;
 }
 }
}

• andrew.fox: Use IHttpClientFactory instead.

Answer 1

Here is a one way to do it

public class ResourceServerRestClient : IResourceServerRestClient
{
 private readonly ITokenProvider _tokenProvider;
 private readonly IJsonManager _jsonManager;
 private HttpClient _client;
 // you can inject the interfaces
 public ResourceServerRestClient(ITokenProvider tokenProvider, IJsonManager jsonManager)
 {
 _tokenProvider = tokenProvider;
 _jsonManager = jsonManager;
 }
 // who set this property?
 public string BaseAddress { get; set; }
 // this is just to demonstrate a simple reuse technique. you can do it in other ways. (singleton, DI, static)
 public HttpClient Client => _client ?? (_client = new HttpClient());
 public Task<T> GetAsync<T>(string uri, string clientId)
 {
 return InvokeAsync<T>(
 clientId,
 client => client.GetAsync(uri),
 response => response.Content.ReadAsAsync<T>());
 }
 public Task<T> PostAsJsonAsync<T>(object data, string uri, string clientId)
 {
 return InvokeAsync<T>(
 clientId,
 client => client.PostAsJsonAsync(uri, data),
 response => response.Content.ReadAsAsync<T>());
 }
 public Task PostAsJsonAsync(object data, string uri, string clientId)
 {
 return InvokeAsync<object>(
 clientId,
 client => client.PostAsJsonAsync(uri, data));
 }
 public Task PutAsJsonAsync(object data, string uri, string clientId)
 {
 return InvokeAsync<object>(
 clientId,
 client => client.PutAsJsonAsync(uri, data));
 }
 public Task<T> PutAsJsonAsync<T>(object data, string uri, string clientId)
 {
 return InvokeAsync<T>(
 clientId,
 client => client.PutAsJsonAsync(uri, data),
 response => response.Content.ReadAsAsync<T>());
 }
 private async Task<T> InvokeAsync<T>(
 string clientId,
 Func<HttpClient, Task<HttpResponseMessage>> operation,
 Func<HttpResponseMessage, Task<T>> actionOnResponse = null)
 {
 if(operation == null)
 throw new ArgumentNullException(nameof(operation));
 // consider to make pre check validation also to clientId argument if it's needed
 var token = GetToken();
 ConfigurateHttpClient(_client, token, clientId);
 HttpResponseMessage response = await operation(_client).ConfigureAwait(false);
 if(!response.IsSuccessStatusCode)
 {
 var exception = new Exception($"Resource server returned an error. StatusCode : {response.StatusCode}");
 exception.Data.Add("StatusCode", response.StatusCode);
 throw exception;
 }
 if(actionOnResponse != null)
 {
 return await actionOnResponse(response).ConfigureAwait(false);
 }
 else
 {
 return default(T);
 }
 }
 private string GetToken()
 {
 // if IsTokenNullOrExpired return null and not string.Empty, you can do the foloowing:
 var token = await _tokenProvider.IsTokenNullOrExpired() ?? await _tokenProvider.GetTokenAsync();
 if(string.IsNullOrEmpty(token))
 {
 var exception = new Exception();
 exception.Data.Add("StatusCode", HttpStatusCode.Unauthorized);
 throw exception;
 }
 //else, do this:
 string token = await _tokenProvider.IsTokenNullOrExpired();
 if(string.IsNullOrEmpty(token))
 {
 token = await _tokenProvider.GetTokenAsync();
 if(string.IsNullOrEmpty(token))
 {
 var exception = new Exception();
 exception.Data.Add("StatusCode", HttpStatusCode.Unauthorized);
 throw exception;
 }
 }
 return token;
 }
 private void ConfigurateHttpClient(HttpClient client, string bearerToken, string resourceServiceClientName)
 {
 // do this first
 if(string.IsNullOrEmpty(BaseAddress))
 {
 throw new Exception("BaseAddress is required!");
 }
 // consider to do pre check also for arguments if it make sense
 if(!string.IsNullOrEmpty(resourceServiceClientName))
 {
 client.DefaultRequestHeaders.Add("CN", resourceServiceClientName);
 }
 client.BaseAddress = new Uri(BaseAddress);
 client.Timeout = new TimeSpan(0, 0, 0, 10);
 client.DefaultRequestHeaders.Accept.Clear();
 client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", bearerToken);
 }
}

I hope it's help..

• Lost_In_Library: Thanks for your answer @Dudi Keleti, I'm reviewing/thinking your code rightnow. But I have one quick question. Can you explain to me in just a few sentences, why all async calls (get,put,post,delete etc.) should use ".ConfigureAwait(false);". I mean, i think, there is no gui or "main thread" in one mvc request to webapi. Why I need to use it?
• Dudi Keleti: because you don't care about capturing the current context. if it was UI work then it will be ConfigureAwait(true). check this for more info
• Lost_In_Library: Is it good to re-create httpClient for every request? I found these: codereview.stackexchange.com/questions/69950/…
• Dudi Keleti: @Lost_In_Library yep the link is correct. reuse the client if there is no reason to recreate. if you want I can update my answer later today.
• Dudi Keleti: @Lost_In_Library done:) if it's seems OK for you, please accept the answer.