NET CORE 2.1和EventSource示例

项目结构

HomeController.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using EventSourceDemo.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;

namespace EventSourceDemo.Controllers
{
    public class HomeController : Controller
    {
        public HomeController(EventsService eventsService,
            ILogger<HomeController> logger)
        {
            //依赖注入事件服务和日志记录器
            // dependency inject the event service and logger
            this.eventsService = eventsService;
            this.logger = logger;

            //理想情况下，这应该通过某种计时器服务来处理这种单一计时器，这种计时器服务可以通过DI推送到这里
            // create a singleton timer in a slightly hacky fashion
            // ideally this should be handled by some sort of timer service
            // that gets pushed into here with DI
            lock (heartbeatTimerLock)
            {
                if (heartbeatTimer == null)
                {
                    heartbeatTimer = new Timer(new TimerCallback(HeartbeatTimerTick), null, 1000, 1000);
                }
            }
        }

        private EventsService eventsService;
        private ILogger<HomeController> logger;

        private static readonly object heartbeatTimerLock = new object();
        private volatile static Timer heartbeatTimer = null;

        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }

        private void HeartbeatTimerTick(object state)
        {
            //每次计时器触发时，它都会发出一个心跳事件，其事件源更新包含当前时间作为字符串
            // every time the timer fires, it will raise a heartbeat event
            // with an event source update that contains the current time
            // as a string
            string currentTimeString = DateTimeOffset.Now.ToString("o");

            eventsService.Notify("heartbeat", new EventSourceUpdate()
            {
                Comment = $"heartbeat {currentTimeString}",
                Event = "Message",
                DataObject = new {Message = currentTimeString}
            });
        }

        [HttpGet]
        public async Task<string> EventSource()
        {
            //根据规范使用事件流内容类型
            // use the event stream content type, as per specification
            HttpContext.Response.ContentType = "text/event-stream";

            //从标题中获取最后一个事件ID
            // get the last event id out of the header
            string lastEventIdString = HttpContext.Request.Headers["Last-Event-ID"].FirstOrDefault();
            int temp;
            int? lastEventId = null;

            if (lastEventIdString != null && int.TryParse(lastEventIdString, out temp))
            {
                lastEventId = temp;
            }

            string remoteIp = HttpContext.Connection.RemoteIpAddress.ToString();


            // open the current request stream for writing.
            // Use UTF-8 encoding, and do not close the stream when disposing.
            using (var clientStream =
                new StreamWriter(HttpContext.Response.Body, Encoding.UTF8, 1024, true) {AutoFlush = true})
            {
                // subscribe to the heartbeat event. Elsewhere, a timer will push updates to this event periodically.
                using (EventSubscription<EventSourceUpdate> subscription =
                    eventsService.SubscribeTo<EventSourceUpdate>("heartbeat"))
                {
                    try
                    {
                        logger.LogInformation($"Opened event source stream to address: {remoteIp}");

                        await clientStream.WriteLineAsync($":connected {DateTimeOffset.Now.ToString("o")}");

                        // If a last event id is given, pump out any intermediate events here.
                        if (lastEventId != null)
                        {
                            // We're not doing anything that stores events in this heartbeat demo,
                            // so do nothing here.
                        }

                        // start pumping out events as they are pushed to the subscription queue
                        while (true)
                        {
                            // asynchronously wait for an event to fire before continuing this loop.
                            // this is implemented with a semaphore slim using the async wait, so it
                            // should play nice with the async framework.
                            EventSourceUpdate update = await subscription.WaitForData();

                            // push the update down the request stream to the client
                            if (update != null)
                            {
                                string updateString = update.ToString();
                                await clientStream.WriteAsync(updateString);
                            }
                        }
                    }
                    catch (Exception e)
                    {
                        // catch client closing the connection
                        logger.LogInformation($"Closed event source stream from {remoteIp}. Message: {e.Message}");
                    }
                }
            }

            return ":closed";
        }

        public IActionResult Contact()
        {
            ViewData["Message"] = "Your contact page.";

            return View();
        }

        public IActionResult Error()
        {
            return View();
        }
    }
}

Services

EventService.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace EventSourceDemo.Services
{
    public class EventsService
    {
        private readonly object collectionsLock = new object();

        //此字典将事件名称链接到该事件的订阅者列表
        // This dictionary links event names to a list of subscribers to that event
        private Dictionary<string, List<EventSubscription>> eventSubscriptionList =
            new Dictionary<string, List<EventSubscription>>();

        //此字典将订阅者链接到他们订阅的列表，以便在取消订阅时快速删除
        // this dictionary links subscribers to the lists that they are subscribed to,
        // for quick removal during unsubscribe
        private Dictionary<EventSubscription, List<List<EventSubscription>>> subscriptionMembershipLists =
            new Dictionary<EventSubscription, List<List<EventSubscription>>>();

        public void Notify(string eventName, object data)
        {
            lock (collectionsLock)
            {
                List<EventSubscription> subscriptions = null;
                if (eventSubscriptionList.TryGetValue(eventName, out subscriptions))
                {
                    //通知所有订阅此事件已发生
                    // notify all subscriptions that this event has occurred
                    NotifyList(subscriptions, data);
                }
            }
        }

        public void NotifyWhere(Func<string, bool> predicate, object data)
        {
            lock (collectionsLock)
            {
                List<EventSubscription> subscriptions = eventSubscriptionList.Where(kvp => predicate(kvp.Key))
                    .SelectMany(kvp => kvp.Value)
                    .Distinct()
                    .ToList();

                NotifyList(subscriptions, data);
            }
        }

        private void NotifyList(List<EventSubscription> subscriptions, object data)
        {
            foreach (EventSubscription thisSubscription in subscriptions)
            {
                thisSubscription.Notify(data);
            }
        }

        public EventSubscription<T> SubscribeTo<T>(params string[] eventNames) where T : class
        {
            if (eventNames == null) throw new ArgumentNullException(nameof(eventNames));
            EventSubscription<T> subscription = new EventSubscription<T>(this);

            lock (collectionsLock)
            {
                List<List<EventSubscription>> eventMemberships = new List<List<EventSubscription>>();
                subscriptionMembershipLists.Add(subscription, eventMemberships);

                foreach (string thisEventName in eventNames)
                {
                    List<EventSubscription> subscriptions = null;
                    if (!eventSubscriptionList.TryGetValue(thisEventName, out subscriptions))
                    {
                        //如果该事件名称不存在，请添加该列表
                        // add the list against this event name if it doesn't exist
                        subscriptions = new List<EventSubscription>();
                        eventSubscriptionList.Add(thisEventName, subscriptions);
                    }

                    //将订阅添加到此订阅列表
                    // add the subscription to this subscriptions list
                    subscriptions.Add(subscription);
                    //将此订阅列表添加到此属于的事件成员资格列表中。
                    // add this subscriptions list to the list of event memberships that this is part of.
                    eventMemberships.Add(subscriptions);
                }
            }

            return subscription;
        }

        public void Unsubscribe(EventSubscription subscription)
        {
            lock (collectionsLock)
            {
                List<List<EventSubscription>> subscriptionsList;
                if (subscriptionMembershipLists.TryGetValue(subscription, out subscriptionsList))
                {
                    foreach (List<EventSubscription> subscriptions in subscriptionsList)
                    {
                        lock (subscriptions)
                        {
                            subscriptions.Remove(subscription);
                        }
                    }

                    subscriptionMembershipLists.Remove(subscription);
                }
            }
        }
    }

    public class DataReceivedEventArgs<T> : EventArgs
    {
        public DataReceivedEventArgs(T data)
        {
        }

        public T Data { get; }
    }

    public abstract class EventSubscription : IDisposable
    {
        public abstract void Dispose();

        public abstract void Notify(object data);
    }

    public class EventSubscription<T> : EventSubscription where T : class
    {
        public event EventHandler<DataReceivedEventArgs<T>> DataReceived;
        private EventsService service;
        private readonly object deliveryQueueLock = new object();
        private Queue<T> deliveryQueue = new Queue<T>();
        private SemaphoreSlim signal = new SemaphoreSlim(0, int.MaxValue);

        public EventSubscription(EventsService service)
        {
            this.service = service;
        }

        public override void Notify(object data)
        {
            T genericData = data as T;

            if (genericData != null)
            {
                Notify(genericData);
            }
        }

        public void Notify(T data)
        {
            //将数据添加到队列以供使用
            // add data to the queue for consumption
            lock (deliveryQueueLock)
            {
                deliveryQueue.Enqueue(data);
            }

            signal.Release();

            //触发事件当发生事件与数据
            // fire event occured event with data
            DataReceived?.Invoke(this, new DataReceivedEventArgs<T>(data));
        }

        public async Task<T> WaitForData()
        {
            await signal.WaitAsync();

            lock (deliveryQueueLock)
            {
                return deliveryQueue.Dequeue();
            }
        }

        public override void Dispose()
        {
            service.Unsubscribe(this);
            signal.Dispose();
        }
    }
}

EventSourceUpdate.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace EventSourceDemo.Services
{
    public class EventSourceUpdate
    {
        public int? Id { get; set; }
        public string Event { get; set; }

        private object dataObject;

        public object DataObject
        {
            get { return this.dataObject; }
            set
            {
                this.dataObject = value;
                this.Data = JsonConvert.SerializeObject(value)
                    .Split(new string[] {Environment.NewLine}, StringSplitOptions.RemoveEmptyEntries)
                    .ToList();
            }
        }

        public List<string> Data { get; private set; }
        public string Comment { get; set; }

        public override string ToString()
        {
            string idStart = "id:";
            string eventStart = "event:";
            string dataStart = "data:";
            string commentStart = ":";

            StringBuilder sb = new StringBuilder();

            if (Comment != null)
            {
                sb.Append(commentStart);
                sb.AppendLine(Comment);
            }

            if (Event != null)
            {
                if (Id != null)
                {
                    sb.Append(idStart);
                    sb.AppendLine(Id.Value.ToString());
                }

                sb.Append(eventStart);
                sb.AppendLine(Event);

                if (Data != null)
                {
                    foreach (string thisDatum in Data)
                    {
                        sb.Append(dataStart);
                        sb.AppendLine(thisDatum);
                    }
                }

                sb.AppendLine();
            }

            return sb.ToString();
        }

        public static EventSourceUpdate FromObject(string eventName, object value, int? id = null)
        {
            return new EventSourceUpdate()
            {
                Id = id,
                Event = eventName,
                DataObject = value
            };
        }
    }
}

Index.cshtml

@{
    ViewData["Title"] = "Home Page";
}
<br />
<div id="display">

div>
@section Scripts {
    <script>
        // setup the event source
        function connectEventSource() {
            console.log("连接到事件源event source ...");

            var eventSourceURL = "@Html.Raw(Url.Action("EventSource", "Home"))";

            if (eventSourceURL !== "") {
                if (!!window.EventSource) {
                    var source = new EventSource(eventSourceURL);
                    console.log("已配置事件源.");
                    // event source successfully connected
                    source.addEventListener('Message', function (e) {
                        dataObject = JSON.parse(e.data);
                        var message = dataObject.Message;
                        console.log("收到消息: " + message);
                        writeLine(message);
                    }, false);

                    source.addEventListener('open', function (e) {
                        // Connection was opened.
                        console.log("事件源连接已打开.");
                        writeLine("事件源已打开");
                    }, false);

                    source.addEventListener('error', function (e) {
                        if (e.readyState == EventSource.CLOSED) {
                            // Connection was closed.
                            console.log("事件源连接已关闭.");
                            writeLine("事件源已关闭");
                        }
                    }, false);

                } else {
                    console.error("您的浏览器不支持事件源.");
                    writeLine("浏览器不支持事件源SSE.");
                }
            }
            else {
                console.error("事件源URL无效");
            }
        }

        function writeLine(message) {
            $("#display").append(message + "
");
        }

        $(document).ready(function () {
            console.log("Document准备好了");
            connectEventSource();
        });

    script>

}

_Layout.cshtml

<html>
<head>
    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <title>@ViewData["Title"] - EventSource示例title>

    <environment names="Development">
        <link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.css"/>
        <link rel="stylesheet" href="~/css/site.css"/>
    environment>
    <environment names="Staging,Production">
        <link rel="stylesheet" href="https://ajax.aspnetcdn.com/ajax/bootstrap/3.3.6/css/bootstrap.min.css"
              asp-fallback-href="~/lib/bootstrap/dist/css/bootstrap.min.css"
              asp-fallback-test-class="sr-only" asp-fallback-test-property="position" asp-fallback-test-value="absolute"/>
        <link rel="stylesheet" href="~/css/site.min.css" asp-append-version="true"/>
    environment>
head>
<body>
<div class="navbar navbar-inverse navbar-fixed-top">
    <div class="container">
        <div class="navbar-header">
            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
                <span class="sr-only">Toggle navigationspan>
                <span class="icon-bar">span>
                <span class="icon-bar">span>
                <span class="icon-bar">span>
            button>
            <a asp-area="" asp-controller="Home" asp-action="Index" class="navbar-brand">EventSourceDemoa>
        div>
        <div class="navbar-collapse collapse">
            <ul class="nav navbar-nav">
                <li>
                    <a asp-area="" asp-controller="Home" asp-action="Index">Homea>
                li>
                <li>
                    <a asp-area="" asp-controller="Home" asp-action="EventSource">Direct Event Streama>
                li>
            ul>
        div>
    div>
div>
<div class="container body-content">
    @RenderBody()
    <hr/>
    <footer>
        <p>© 2019 - EventSource示例p>
    footer>
div>

<environment names="Development">
    <script src="~/lib/jquery/dist/jquery.js">script>
    <script src="~/lib/bootstrap/dist/js/bootstrap.js">script>
    <script src="~/js/site.js" asp-append-version="true">script>
environment>
<environment names="Staging,Production">
    <script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-2.2.0.min.js"
            asp-fallback-src="~/lib/jquery/dist/jquery.min.js"
            asp-fallback-test="window.jQuery">
    script>
    <script src="https://ajax.aspnetcdn.com/ajax/bootstrap/3.3.6/bootstrap.min.js"
            asp-fallback-src="~/lib/bootstrap/dist/js/bootstrap.min.js"
            asp-fallback-test="window.jQuery && window.jQuery.fn && window.jQuery.fn.modal">
    script>
    <script src="~/js/site.min.js" asp-append-version="true">script>
environment>

@RenderSection("scripts", required: false)
body>
html>

_ViewImports.cshtml

@using EventSourceDemo
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

_ViewStart.cshtml

@{
    Layout = "_Layout";
}

Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace coreEventSource
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseKestrel()
                .UseContentRoot(Directory.GetCurrentDirectory())
                .UseStartup<Startup>();
    }
}

Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using EventSourceDemo.Services;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace coreEventSource
{
    public class Startup
    {

        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

        public IConfigurationRoot Configuration { get; }


        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc();

            // Add logging
            services.AddLogging();

            // Add the event coordination service
            services.AddSingleton<EventsService>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                //app.UseBrowserLink();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
            }

            app.UseStaticFiles();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "short",
                    template: "{action=Index}/{id?}",
                    defaults: new { controller = "Home" });

                routes.MapRoute(
                    name: "default",
                    template: "{controller=Home}/{action=Index}/{id?}");
            });


            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            //app.Run(async (context) =>
            //{
            //    await context.Response.WriteAsync("Hello World!");
            //});
        }
    }
}

launchSettings.json

{
  "iisSettings": {
    "windowsAuthentication": false, 
    "anonymousAuthentication": true, 
    "iisExpress": {
      "applicationUrl": "http://localhost:51261",
      "sslPort": 0
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "coreEventSource": {
      "commandName": "Project",
      "launchBrowser": true,
      "applicationUrl": "http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

如图: