Startup.cs

// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
using System;
using System.Net.Mime;
using CloudNative.CloudEvents;
using CloudNative.CloudEvents.AspNetCore;
using CloudNative.CloudEvents.NewtonsoftJson;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace event_display_with_reply
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILogger<Startup> logger)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            logger.LogInformation("Service is starting...");

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapPost("/", async context =>
                {
                    var formatter = new JsonEventFormatter();
                    var cloudEvent = await context.Request.ToCloudEventAsync(formatter);
                    logger.LogInformation("Received CloudEvent\n" + GetEventLog(cloudEvent));

                    var replyEvent = GetEventReply();
                    logger.LogInformation("Replying with CloudEvent\n" + GetEventLog(replyEvent));

                    await replyEvent.CopyToHttpResponseAsync(context.Response, ContentMode.Binary, formatter);
                });
            });
        }

        private CloudEvent GetEventReply()
        {
            return new CloudEvent
            {
                Id = Guid.NewGuid().ToString(),
                DataContentType = MediaTypeNames.Application.Json,
                Data = new { key = "This is a Knative reply" },
                Type = "dev.knative.samples.hifromknative",
                Source = new Uri("urn:knative/eventing/samples/hello-world"),
            };
        }

        private string GetEventLog(CloudEvent cloudEvent)
        {
            return $"ID: {cloudEvent.Id}\n"
                + $"Source: {cloudEvent.Source}\n"
                + $"Type: {cloudEvent.Type}\n"
                + $"Subject: {cloudEvent.Subject}\n"
                + $"DataSchema: {cloudEvent.DataSchema}\n"
                + $"DataContentType: {cloudEvent.DataContentType}\n"
                + $"Time: {cloudEvent.Time?.ToUniversalTime():yyyy-MM-dd'T'HH:mm:ss.fff'Z'}\n"
                + $"SpecVersion: {cloudEvent.SpecVersion}\n"
                + $"Data: {cloudEvent.Data}";
        }
    }
}