Windows Azure Service Bus Notification Hub推送通知

前言

随着Windows Azure 在中国的正式落地，相信越来越多的人会体验到Windows Azure带来的强大和便利。在上一篇文章中，我们介绍了如何利用Windows Azure中的Service Bus的中继功能(Relay)，来将您的WCF服务册到Windows Azure Service Bus上。而WCF客户端可以通过访问Service Bus endpoint, 从而访问到您真正的WCF服务。
在这篇文章中，我们将介绍Windows Azure Service Bus的另外一个功能：通知中心(Notification Hub)。（说明：该功能目前还处于Preview阶段）
在很多应用系统中，通过Publisher |Subscriber 模型来实现消息推送是一个常用的功能。实现方法也有很多,且较为复杂。幸运的是，在Windows Azure Service Bus中，我们提供一个功能：通知中心(Notification Hub)，可以非常方便地实现大批量的推送通知的功能。
下面，我就以开发一个简单的Windows 8 application为例，介绍如何利用这个功能实现Toast notification。

前提条件

1. 开发环境：Visual Studio 2012 + Windows 8
2. Windows Azure 账号 (您可以通过以下地址免费申请一个: http://www.azure.com)
3. Windows 8开发者账号。
4. Service Bus WinRT Preview SDK (http://go.microsoft.com/fwlink/?LinkID=277160)

正文

第一部分：配置

1. 首先，您可以创建一个用于演示的Windows Store application。为了接收推送下来的Toast Notification,您必须先要开启该功能，如下所示：

2. 然后，将该application和Windows Store关联起来，并在Windows Store里面正确配置该application, 比如Notification等等，并获取正确的Package Security Identifier (SID) 和Client secret。

里面最关键的一步，是要配置你的application的推送通知的功能，并获得相应的Package Security Identifier (SID) 和Client secret。
比如：下面就是我配置后生成的相应SID和Client secret:

3. 接下来，我们需要回到Windows Azure Management Portal, 创建一个Notification Hub。比如，我在namesapce4push下，创建了一个叫做myhub的 Notification Hub,如下所示：

4. 然后，给刚才创建的Notification Hub : myhub 指定相应的Package SID和Client Secret,使得我们自己开发的application和该notification hub关联起来，如下所示：

最后点击保存。

5. 上述设置结束之后，回到Visual Studio，其会自动检测到这一行为，点击下一步直至结束，这样该application和store成功关联起来了。

第二部分：编写代码

1. 在application里面，我们需要在程序启动的时候，完成一些初始化的动作，比如该application在Notification Hub的注册等。
下面用黄色高亮显示的部分为相关代码：

using PushDemo.Common;

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using System.Threading.Tasks;

using Microsoft.WindowsAzure.Messaging;
using Windows.Networking.PushNotifications;
using Windows.UI.Notifications;
using Windows.Data.Xml.Dom;

// The Grid App template is documented at http://go.microsoft.com/fwlink/?LinkId=234226

namespace PushDemo
{
    /// <summary>
    /// Provides application-specific behavior to supplement the default Application class.
    /// </summary>
    sealed partial class App : Application
    {
        /// <summary>
        /// Initializes the singleton Application object.  This is the first line of authored code
        /// executed, and as such is the logical equivalent of main() or WinMain().
        /// </summary>
        /// 

        NotificationHub notificationHub;

        public App()
        {
            var cn = ConnectionString.CreateUsingSharedAccessSecretWithListenAccess(
                new Uri("sb://namespace4push.servicebus.windows.net/"),
                "******<listenAccessSecret>******"
                );

            notificationHub = new NotificationHub("myhub", cn);

            this.InitializeComponent();
            this.Suspending += OnSuspending;
        }


        async Task InitializeNotificationsAsync()
        {
            var channel = await PushNotificationChannelManager.CreatePushNotificationChannelForApplicationAsync();
            await notificationHub.RefreshChannelUriAsync(channel.Uri);

            if (!await notificationHub.TemplateRegistrationExistsAsync("myToastRegistration"))
                await notificationHub.CreateTemplateRegistrationAsync(BuildTextToastTemplate(), "myToastRegistration");
        }


        XmlDocument BuildTextToastTemplate()
        {
            var template =
                ToastNotificationManager.GetTemplateContent(ToastTemplateType.ToastText01);
            var textNode = template.SelectSingleNode("//text[@id='1']") as XmlElement;
            if (textNode != null)
            {
                textNode.InnerText = "$(msg)";
            }
            return template;
        }

        /// <summary>
        /// Invoked when the application is launched normally by the end user.  Other entry points
        /// will be used when the application is launched to open a specific file, to display
        /// search results, and so forth.
        /// </summary>
        /// <param name="args">Details about the launch request and process.</param>
        protected override async void OnLaunched(LaunchActivatedEventArgs args)
        {
            await InitializeNotificationsAsync();

            Frame rootFrame = Window.Current.Content as Frame;

            // Do not repeat app initialization when the Window already has content,
            // just ensure that the window is active
            
            if (rootFrame == null)
            {
                // Create a Frame to act as the navigation context and navigate to the first page
…
…
            }
            // Ensure the current window is active
            Window.Current.Activate();
        }

        /// <summary>
        /// Invoked when application execution is being suspended.  Application state is saved
        /// without knowing whether the application will be terminated or resumed with the contents
        /// of memory still intact.
        /// </summary>
        /// <param name="sender">The source of the suspend request.</param>
        /// <param name="e">Details about the suspend request.</param>
…
…
    }
}

2. 接下来我们需要一个用来推送消息的后台程序。我们就用一个非常简单的windows console程序来模拟后台好了。相关的代码如下：

class Program
    {
        static void Main(string[] args)
        {
            var cn = ServiceBusConnectionStringBuilder.CreateUsingSharedAccessKey(
                new Uri("sb://namespace4push.servicebus.windows.net/"),
                Microsoft.ServiceBus.Notifications.NotificationHubDescription.DefaultFullSasRuleName,
                "*****<Access key>********”
                );

            var hbClient = Microsoft.ServiceBus.Notifications.NotificationHubClient.CreateClientFromConnectionString(cn, "myhub");
            hbClient.SendTemplateNotification(new Dictionary<string, string>
            {
               {"msg",args.Length>0? args[0]:"Hello World, Service Bus Notification Hub"}
            }
            );
        }
   }