Skip to main content

A Sample On HttpClientFactory Using Typed Client Technique In .Net Core Application

In .Net Core, using HttpClientFacotory is the recommended way to consume the Rest API. The HttpClientFactory can be implemented using the following techniques.

Typed Client:

Typed Client technique is to implement or create a separate entity or class file per API domain. So all Http communication implementations are registered in a specific class per API domain. In this approach, each entity or class will be injected with 'System.Net.Http.HttpClient' object by the 'HttpClienFacotry'. So in this approach, we will not use 'HttpClientFactory' directly like we did for 'Named Client' and 'Using HttpRequestMessage Object' techniques.

In simple words for consuming one third-party rest API need to create a specific class for it, if we have 'n' number of rest APIs to consume in our project then we need to create 'n' number of classes to implement the HttpClientFactory logic specific to the domains of rest APIs.

HttpClientFactory Request Flow:


Click here for a better understanding of the working flow of HttpClientFactory.

ThirdParty Test APIs:

So to understand and implement a sample on HttpClientFactory using the named technique we need to have external APIs. So were are going to use freely hosted rest APIs for a developer to use and learn like below:
JSONPlaceholder:
https://jsonplaceholder.typicode.com/

Dummy Rest API:
http://dummy.restapiexample.com/

Create A .Net Core Sample API Project:

To understand and to learn the Typed Client technique of HttpClientFactory we are going to do a sample application. So to start for creating a sample application we can use either Visual Studio 2019 or Visual Studio Code.

Install NewtonSoft.Json Package:

For easy steps to serialize and deserialize of JSON response, we are going to use the NewtonSoft.JSON package.
CLI Command:

dotnet add package Newtonsoft.Json
PackageManager:

Install-Package Newtonsoft.Json

Create A Typed Client Of JSONPlaceHolder Rest API:

Now to consume the 'Todos' endpoint of 'JsonPlaceHolder' Rest API we are going to create a separate typed client.
RestCalls/JsonPlaceHolderClient.cs:
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using TypedClientApi.Model;

namespace TypedClientApi.RestCalls
{
    public class JsonPlaceHolderClient
    {
        public readonly HttpClient _httpClient;

        public JsonPlaceHolderClient(HttpClient httpClient)
        {
            httpClient.BaseAddress = new Uri("https://jsonplaceholder.typicode.com");
            _httpClient = httpClient;
        }
    }
}
  • 'JsonPlaceHolderClient.cs' is a Typed Client of 'JsonPlaceHolder' API, all GET, POST, DELETE action methods will implemented in this class.
  • 'System.Net.Http.HttpClient' object injected into our typed client. In this approach, HttpClientFacotry will not be used directly.
  • In this constructor we can configure our HttpClient object with 'domain', 'default-headers','default-keys', etc. These default configurations can also be configured at the 'Startup.cs' file also.
Since we are going to consume the todos object, let's create 'Todo.cs' to hold the API response data.
Model/Todo.cs:
namespace TypedClientApi.Model
{
    public class Todo
    {
        public int UserId { get; set; }
        public int Id { get; set; }
        public string Title { get; set; }
        public bool Completed { get; set; }
    }
}
Now let's implement 'Todos' endpoint get method as follows:
RestCalls/JsonPlaceHolderClient.cs:
public async Task<List<Todo>> GetTodos()
{
	var response = await _httpClient.GetAsync("/todos");

	if (response.IsSuccessStatusCode)
	{
		string responseString = await response.Content.ReadAsStringAsync();
		List<Todo> todos = JsonConvert.DeserializeObject<List<Todo>>(responseString);
		return todos;
	}
	return new List<Todo>();
}
  • (Line 3) HttpClient object is used to trigger the 'Todo' endpoint. The HttpClient object is made of all asynchronous operations like 'GetAsync', 'PostAsync', 'DeleteAsync' etc. Since we assigned the domain name at the time of constructor initialization, so for endpoints can be declared with a relative path.
  • So on receiving the successful response, we deserialize the response to the object.
Now register the 'JsonPlaceHoderClient' typed client in the Startup.cs file to make this typed client available to HttpClientFactory. So on registering in the 'Startup.cs' file, the typed client(eg: 'JsonPlaceHolderClient') will become the injectable service.
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
	services.AddControllers();
	services.AddHttpClient<JsonPlaceHolderClient>();
}
Let's write a 'Test' controller endpoint to consume this 'Todo' API as follows:
Controllers/TestController.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using TypedClientApi.Model;
using TypedClientApi.RestCalls;

namespace TypedClientApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class TestController : ControllerBase
    {
        private readonly JsonPlaceHolderClient _jsonPlaceHolderClient;
        public TestController(JsonPlaceHolderClient jsonPlaceHolderClient)
        {
            _jsonPlaceHolderClient = jsonPlaceHolderClient;
        }

        [HttpGet]
        [Route("all-todos")]
        public async Task<IActionResult> GetTodos()
        {
            List<Todo> todos = await _jsonPlaceHolderClient.GetTodos();
            return Ok(todos);
        }
    }
}
  • (Line: 17) 'JsonPlaceHolderClient' rest-client injected to our test controller.
  • (Line: 22-28) get action method to fetch all todos
Now run the application and checks the todo's JSON response data as below.

Create A Type Client Of DummyExampleRestAPI:

Here we are creating a new 'DummyExampleRestAPI' to understand how it looks in the real-time application while using the Typed Client technique.

The employee endpoint of 'DummyExampleRestAPI' response objects to be created like below.
Models/Employee.cs:
using Newtonsoft.Json;
using System.Collections.Generic;

namespace TypedClientApi.Model
{
    public class Employee
    {
        [JsonProperty(PropertyName = "id")]
        public string Id { get; set; }

        [JsonProperty(PropertyName = "employee_name")]
        public string EmployeeName { get; set; }
        [JsonProperty(PropertyName = "employee_salary")]
        public string EmployeeSalary { get; set; }
        [JsonProperty(PropertyName = "employee_age")]
        public string EmplyeeAge { get; set; }
        [JsonProperty(PropertyName = "profile_image")]
        public string ProfileImage { get; set; }
    }

    public class DummyExampleApiResult
    {
        public string Status { get; set; }
        public List<Employee> Data { get; set; }
    }
}
Now let's implement 'DummyExampleRestAPI' typed client as below:
RestCalls/DummyExampleRestClient.cs:
using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Threading.Tasks;
using TypedClientApi.Model;

namespace TypedClientApi.RestCalls
{
    public class DummyExampleRestClient
    {
        private readonly HttpClient _httpClient;
        public DummyExampleRestClient(HttpClient httpClient)
        {
            httpClient.BaseAddress = new Uri("http://dummy.restapiexample.com");
            _httpClient = httpClient;
        }

        public async Task<DummyExampleApiResult> GetEmployees()
        {
            var response = await _httpClient.GetAsync("/api/v1/employees");
            if (response.IsSuccessStatusCode)
            {
                string responseString = await response.Content.ReadAsStringAsync();
                DummyExampleApiResult employees = JsonConvert.DeserializeObject<DummyExampleApiResult>(responseString);
                return employees;
            }
            return new DummyExampleApiResult();
        }
    }
}
Now register 'DummyExampleRestClient' in startup.cs as below:
Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
	services.AddControllers();
	services.AddHttpClient<JsonPlaceHolderClient>();
	services.AddHttpClient<DummyExampleRestClient>();
}
Now inject our 'DummyExampleRestClient' into the TestController as below:
Controllers/TesController.cs:
private readonly JsonPlaceHolderClient _jsonPlaceHolderClient;
private readonly DummyExampleRestClient _dummyExampleRestClient;
public TestController(
	JsonPlaceHolderClient jsonPlaceHolderClient,
	DummyExampleRestClient dummyExampleRestClient)
{
	_jsonPlaceHolderClient = jsonPlaceHolderClient;
	_dummyExampleRestClient = dummyExampleRestClient;
}
Now add get action methods to fetch employee data as below:
Controllers/TestController.cs:
[HttpGet]
[Route("all-employee")]
public async Task<IActionResult> GetEmployees()
{
	DummyExampleApiResult employees = await _dummyExampleRestClient.GetEmployees();
	return Ok(employees);
}

Now run the application and checks the JSON response data of employee endpoint like below:

Default HttpClient Configuration At Startup.Cs:

On recalling the previous steps we know that API 'domain', 'default-headers', 'default-keys' can be configured in typed client constructor. But we have another option to configure them in the startup .cs file at the time of registering those typed clients

Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
	services.AddControllers();
	services.AddHttpClient<JsonPlaceHolderClient>(client =>
	{
		client.BaseAddress = new Uri("https://jsonplaceholder.typicode.com");
		//client.DefaultRequestHeaders
		// client.Timeout
		// client.DefaultRequestVersion
	});
	services.AddHttpClient<DummyExampleRestClient>(client =>
	{
		client.BaseAddress = new Uri("http://dummy.restapiexample.com");
		//client.DefaultRequestHeaders
		// client.Timeout
		// client.DefaultRequestVersion
	});
}  
Now we can remove the default configurations from the constructor in the typed clients as below:
namespace TypedClientApi.RestCalls
{
    public class JsonPlaceHolderClient
    {
        public readonly HttpClient _httpClient;

        public JsonPlaceHolderClient(HttpClient httpClient)
        {
            _httpClient = httpClient;
        }
    }
}

namespace TypedClientApi.RestCalls
{
    public class DummyExampleRestClient
    {
        private readonly HttpClient _httpClient;
        public DummyExampleRestClient(HttpClient httpClient)
        
            _httpClient = httpClient;
        }
    }
}
Finally, we have implemented a sample using the Typed Client technique in .net core application.

Support Me!
Buy Me A Coffee PayPal Me

Wrapping Up:

Hopefully, I think this article delivered some useful information about HttpClient implementation using the Typed Client technique in .Net Core Application. I love to have your feedback, suggestions, and better techniques in the comment section below.

Follow Me:

Comments

Popular posts from this blog

.NET6 Web API CRUD Operation With Entity Framework Core

In this article, we are going to do a small demo on AspNetCore 6 Web API CRUD operations. What Is Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, desktop apps. In simple terminology API(Application Programming Interface) means an interface module that contains a programming function that can be requested via HTTP calls to save or fetch the data for their respective clients. Some of the key characteristics of API: Supports HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Supports default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. The ideal platform to build REST full services. Create A .NET6 Web API Application: Let's create a .Net6 Web API sample application to accomplish our

Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication. Main Building Blocks Of Blazor WebAssembly Authentication: The core concepts of blazor webassembly authentication are: AuthenticationStateProvider Service AuthorizeView Component Task<AuthenticationState> Cascading Property CascadingAuthenticationState Component AuthorizeRouteView Component AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider. AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider

How Response Caching Works In Asp.Net Core

What Is Response Caching?: Response Caching means storing of response output and using stored response until it's under it's the expiration time. Response Caching approach cuts down some requests to the server and also reduces some workload on the server. Response Caching Headers: Response Caching carried out by the few Http based headers information between client and server. Main Response Caching Headers are like below Cache-Control Pragma Vary Cache-Control Header: Cache-Control header is the main header type for the response caching. Cache-Control will be decorated with the following directives. public - this directive indicates any cache may store the response. private - this directive allows to store response with respect to a single user and can't be stored with shared cache stores. max-age - this directive represents a time to hold a response in the cache. no-cache - this directive represents no storing of response and always fetch the fr

A Small Guide On NestJS Queues

NestJS Application Queues helps to deal with application scaling and performance challenges. When To Use Queues?: API request that mostly involves in time taking operations like CPU bound operation, doing them synchronously which will result in thread blocking. So to avoid these issues, it is an appropriate way to make the CPU-bound operation separate background job.  In nestjs one of the best solutions for these kinds of tasks is to implement the Queues. For queueing mechanism in the nestjs application most recommended library is '@nestjs/bull'(Bull is nodejs queue library). The 'Bull' depends on Redis cache for data storage like a job. So in this queueing technique, we will create services like 'Producer' and 'Consumer'. The 'Producer' is used to push our jobs into the Redis stores. The consumer will read those jobs(eg: CPU Bound Operations) and process them. So by using this queues technique user requests processed very fastly because actually

Usage Of CancellationToken In Asp.Net Core Applications

When To Use CancellationToken?: In a web application request abortion or orphan, requests are quite common. On users disconnected by network interruption or navigating between multiple pages before proper response or closing of the browser, tabs make the request aborted or orphan. An orphan request can't deliver a response to the client, but it will execute all steps(like database calls, HTTP calls, etc) at the server. Complete execution of an orphan request at the server might not be a problem generally if at all requests need to work on time taking a job at the server in those cases might be nice to terminate the execution immediately. So CancellationToken can be used to terminate a request execution at the server immediately once the request is aborted or orphan. Here we are going to see some sample code snippets about implementing a CancellationToken for Entity FrameworkCore, Dapper ORM, and HttpClient calls in Asp.NetCore MVC application. Note: The sample codes I will show in

.Net5 Web API Managing Files Using Azure Blob Storage

In this article, we are going to understand the different file operations like uploading, reading, downloading, and deleting in .Net5 Web API application using Azure Blob Storage. Azure Blob Storage: Azure blob storage is Microsoft cloud storage. Blob storage can store a massive amount of file data as unstructured data. The unstructured data means not belong to any specific type, which means text or binary data. So something like images or pdf or videos to store in the cloud, then the most recommended is to use the blob store. The key component to creating azure blob storage resource: Storage Account:- A Storage account gives a unique namespace in Azure for all the data we will save. Every object that we store in Azure Storage has an address. The address is nothing but the unique name of our Storage Account name. The combination of the account name and the Azure Storage blob endpoint forms the base address for each object in our Storage account. For example, if our Storage Account is n

.Net5 Web API Redis Cache Using StackExchange.Redis.Extensions.AspNetCore Library

In this article, we are going to explore the integration of Redis cache in .Net5 Web API application using the 'StackExchange.Redis.Exntensions' library. Note:- Microsoft has introduced an 'IDistributedCache' interface in dotnet core which supports different cache stores like In-Memory, Redis, NCache, etc. It is simple and easy to work with  'IDistributedCache', for the Redis store with limited features but if we want more features of the Redis store we can choose to use 'StackExchange.Redis.Extensions'.  Click here for Redis Cache Integration Using IDistributedCache Interface . Overview On StackExchange.Redis.Extnesions Library: The 'StackExchange.Redis.Extension' library extended from the main library 'StackExchange.Redis'. Some of the key features of this library like: Default serialization and deserialization. Easy to save and fetch complex objects. Search key. Multiple Database Access Setup Redis Docker Instance: For this sampl

Part-1 Angular JWT Authentication Using HTTP Only Cookie[Angular V13]

In this article, we are going to implement a sample angular application authentication using HTTP only cookie that contains a JWT token. HTTP Only JWT Cookie: In a SPA(Single Page Application) Authentication JWT token either can be stored in browser 'LocalStorage' or in 'Cookie'. Storing JWT token inside of the cookie then the cookie should be HTTP Only. The HTTP-Only cookie nature is that it will be only accessible by the server application. Client apps like javascript-based apps can't access the HTTP-Only cookie. So if we use authentication with HTTP only JWT cookie then we no need to implement custom logic like adding authorization header or storing token data, etc at our client application. Because once the user authenticated cookie will be automatically sent to the server by the browser on every API call. Authentication API: To implement JWT cookie authentication we need to set up an API. For that, I had created a mock authentication API(Using the NestJS Se

Endpoint Routing In Asp.Net Core

How Routing Works In  Core 2.1 And Below Versions?: In Asp.Net Core routing is configured using app.UseRouter() or app.UseMvc() middleware. app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); Here in Dotnet Core version 2.1 or below versions on the execution of route middleware request will be navigated appropriate controller matched to the route. An operation or functionality which is dependent on route URL or route values and that need to be implemented before the execution of route middleware can be done by accessing the route path from the current request context as below app.Use(async (context, next) => { if(context.Request.Path.Value.IndexOf("oldvehicle") != -1) { context.Response.Redirect("vehicle"); } else { await next(); } }); app.UseMvc(routes => { routes.MapRoute( name: "vehicleRoute", template: "vehicle", defaul

Unit Testing Asp.NetCore Web API Using xUnit[.NET6]

In this article, we are going to write test cases to an Asp.NetCore Web API(.NET6) application using the xUnit. xUnit For .NET: The xUnit for .Net is a free, open-source, community-focused unit testing tool for .NET applications. By default .Net also provides a xUnit project template to implement test cases. Unit test cases build upon the 'AAA' formula that means 'Arrange', 'Act' and 'Assert' Arrange - Declaring variables, objects, instantiating mocks, etc. Act - Calling or invoking the method that needs to be tested. Assert - The assert ensures that code behaves as expected means yielding expected output. Create An API And Unit Test Projects: Let's create a .Net6 Web API and xUnit sample applications to accomplish our demo. We can use either Visual Studio 2022 or Visual Studio Code(using .NET CLI commands) to create any.Net6 application. For this demo, I'm using the 'Visual Studio Code'(using the .NET CLI command) editor. Create a fo