[C#/ASP.NET MVC/.NETCORE] HttpClientBuilderExtensions 클래스 : AddHttpMessageHandler 확장 메소드를 사용해 위임 처리기 사용하기

▶ Handlers/ValidateHeaderHandler.cs

using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace TestProject.Handlers
{
    /// <summary>
    /// 헤더 검증 핸들러
    /// </summary>
    public class ValidateHeaderHandler : DelegatingHandler
    {
        //////////////////////////////////////////////////////////////////////////////////////////////////// Method
        ////////////////////////////////////////////////////////////////////////////////////////// Protected

        #region 송신하기 (비동기) - SendAsync(request, cancellationToken)

        /// <summary>
        /// 송신하기 (비동기)
        /// </summary>
        /// <param name="httpRequestMessage">HTTP 요청 메시지</param>
        /// <param name="cancellationToken">취소 토큰</param>
        /// <returns>HTTP 응답 메시지 태스크</returns>
        protected override async Task<HttpResponseMessage> SendAsync
        (
            HttpRequestMessage httpRequestMessage,
            CancellationToken  cancellationToken
        )
        {
            if(!httpRequestMessage.Headers.Contains("X-API-KEY"))
            {
                return new HttpResponseMessage(HttpStatusCode.BadRequest)
                {
                    Content = new StringContent("You must supply an API key header called X-API-KEY")
                };
            }

            return await base.SendAsync(httpRequestMessage, cancellationToken);
        }

        #endregion
    }
}

 

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▶ Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;

using TestProject.Handlers;

namespace TestProject
{
    /// <summary>
    /// 시작
    /// </summary>
    public class Startup
    {
        //////////////////////////////////////////////////////////////////////////////////////////////////// Property
        ////////////////////////////////////////////////////////////////////////////////////////// Public

        #region 구성 - Configuration

        /// <summary>
        /// 구성
        /// </summary>
        public IConfiguration Configuration { get; }

        #endregion

        //////////////////////////////////////////////////////////////////////////////////////////////////// Constructor
        ////////////////////////////////////////////////////////////////////////////////////////// Public

        #region 생성자 - Startup(configuration)

        /// <summary>
        /// 생성자
        /// </summary>
        /// <param name="configuration">구성</param>
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        #endregion

        //////////////////////////////////////////////////////////////////////////////////////////////////// Method
        ////////////////////////////////////////////////////////////////////////////////////////// Public

        #region 서비스 컬렉션 구성하기 - ConfigureServices(services)

        /// <summary>
        /// 서비스 컬렉션 구성하기
        /// </summary>
        /// <param name="services">서비스 컬렉션</param>
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddTransient<ValidateHeaderHandler>();

            services.AddHttpClient
            (
                "test",
                client =>
                {
                    // X-API-KEY가 필요한 "외부" 서비스라고 가정한다.
                    client.BaseAddress = new Uri("https://localhost:5001/");
                }
            )
            .AddHttpMessageHandler<ValidateHeaderHandler>();

            services.AddControllersWithViews();
        }

        #endregion
        #region 구성하기 - Configure(app, environment)

        /// <summary>
        /// 구성하기
        /// </summary>
        /// <param name="app">애플리케이션 빌더</param>
        /// <param name="environment">웹 호스트 환경</param>
        public void Configure(IApplicationBuilder app, IWebHostEnvironment environment)
        {
            if(environment.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");

                app.UseHsts();
            }

            app.UseHttpsRedirection();

            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints
            (
                endpoints =>
                {
                    endpoints.MapControllerRoute
                    (
                        name    : "default",
                        pattern : "{controller=Home}/{action=Index}/{id?}"
                    );
                }
            );
        }

        #endregion
    }
}

※ 위임 처리기를 사용하는 코드는 없으며 설정하는 코드만 있는 예제이다.