Microsoft SQL Server 2005 Developer’s Guide- P19 doc

Chapter 5: Developing with Notification Services 159 Next, add an import directive for the NotificationServices namespace to the Declarations section of your project. Using the import directive enables you to use the classes in the NotificationServices namespace without requiring you to fully qualify the names. The import directive appears as follows: Imports Microsoft.SqlServer.NotificationServices After adding the reference to your project and its associated namespace, you can create the code to add a subscriber to your Notification Services application. Listing Subscriptions To list the subscriptions that have been created on a Notification Services instance, you can use the SubscriberEnumeration object as is shown in the following listing: ' Create the Instance object Dim myNSInstance As New NSInstance("NSAppInstance") 'Populate the list box Dim oSubscribers As SubscriberEnumeration = New _ SubscriberEnumeration(myNSInstance) ListBox1.Items.Clear() ' Iterate through a collection Figure 5-7 Adding a reference to the Notification Services library 160 Microsoft SQL Server 2005 Developer’s Guide For Each oSub As Subscriber In oSubscribers ' Add each Subscriber Name to the List ListBox1.Items.Add(oSub.SubscriberId) Next At the top of this listing you can see where the Notification Services instance called MyNSInstance is created. The important thing to notice in this line is the fact that the value “MSAppInstance” must match the value defined in your ICF file. This value can also been found by using SQL Server Management Studio to open the Notification Services node that lists the active instances. Next, a new instance of the SubscriberEnumeration object called oSubscribers is created and a For-Each loop is used to iterate through the collection of subscribers exposed by the SubscriberEnumeration object. Within the For-Each loop the name of each subscriber is added to a ListBox that can be displayed to the end user. Adding Subscriptions Of course, before you can list subscribers you must first add them. The following code sample shows how you can add a subscription using the Notification Services managed code API: ' Create the Instance object Dim myNSInstance As New NSInstance("NSAppInstance") ' Create the Application object Dim myNSApp As New NSApplication(myNSInstance, "NSApp") ' Create the Subscriber Dim oSubscriber As New Subscriber(myNSInstance) oSubscriber.SubscriberId = TextSub.Text oSubscriber.Add() ' Add a device for the subscriber ' DeviceName must match subscription Dim oDevice As New SubscriberDevice(myNSInstance) oDevice.DeviceName = "myDevice" oDevice.SubscriberId = TextSub.Text oDevice.DeviceTypeName = "File" oDevice.DeviceAddress = TextSub.Text & "@teca.com" oDevice.DeliveryChannelName = "FileChannel" oDevice.Add() ' Create the subscription Dim oSubscription As New Subscription(myNSApp, "ShipStore") oSubscription("DeviceName") = "myDevice" Chapter 5: Developing with Notification Services 161 oSubscription("SubscriberLocale") = "en-US" oSubscription.SubscriberId = TextSub.Text ' Hard code the store ID for the example oSubscription("StoreID") = 1 'Dim sSubId As String = oSubscription.Add() oSubscription.Add() 'Display the new Subscriber ID ListBox1.Items.Add(TextSub.Text) TextSub.Text = "" First a Notification Services instance object named myNSInstance is created, followed by an Application object named myNSApp. These must correspond to the definitions that were previously defined in the XML-based Notification Services configuration file. For this example, the NSInstance object must be created using the value of “NSAppInstance,” which must match the name of the Notifications Services Instance as defined in the <InstanceName> element of the ICF file. Likewise, the Application object, NSApplication, must use the value of “NSApp” to match the value used in the <ApplicationName> element of the ICF file. You can also see these values beneath the Notification Services node in the SQL Server Management Studio. Next, a Subscriber must be created and notification delivery devices must be added to the subscriber. A new subscriber is created by passing the Notification Services Instance name to the Subscriber object’s constructor. Once the Subscriber object has been instantiated, the SubscriberID property is set with a string value that identifies the subscriber. Here that value comes from a Textbox named TextSub. Then the Add method is called to create the subscriber. As you might expect, the Delete and Update methods must be used if you subsequently want to modify or delete the subscriber information. NOTE Adding a subscriber updates the NSDataSubSubscriptions table along with a couple of other tables in the NSAppInstanceNSApp database. However, you should not directly update these tables. Instead, you should only add, update, and delete subscribers using the NotificationServices API or the stored procedure generated with the Notification Services application. Once the subscriber has been added, at least one device must be added to the subscriber using the SubscriberDevice object. The SubscriberId in combination with the DeviceName property uniquely identifies the device in the system. The value used for the DeliveryChannel property specifies the method by which the notification will 162 Microsoft SQL Server 2005 Developer’s Guide be generated. In this example, the notification will be created in the file system. The actual output file was defined in the ICF file and will be named NSAppNotification .htm. You might notice that the device and the subscriber are defined separately. This enables a subscriber to have multiple notification delivery mechanisms. The Add method is then used to add the device. Once the subscriber has been created and a device has been added for the subscriber, you can then create a subscription. The subscription links the subscriber to a specific event. When you create a new subscription object, you pass in the Application object followed by the name of the subscription class that was defined in your ADF file. In this case, the subscription class was named “ShipStore.” Next, the Subscription object’s properties are assigned values. You should note that the StoreID is assigned a hard-coded value of 1. This essentially creates a subscription for the subscriber to shipment data for StoreID 1. Then, the Add method is called to actually add the subscription to the database. At the end of this code, the subscriber’s name is also added to a ListBox that will be displayed to the end user. NOTE If you get an ArgumentOutOfRangeException while attempting to create a subscription, it typically means that the values you’ve passed to the subscription object do not match the values that were created in the subscribers section of the acf.xml file. You can view the subscribers and the devices that have been added by querying the NSSubscriberDeviceView, as shown in the following listing. For this sample application, the view is found in the NSAppInstanceNSMain database. As mentioned earlier, the name of this database is based in the name of the Notification Services application. View subscribers and devices USE NSAppInstanceNSMain SELECT * FROM NSSubscriberDeviceView The NSShipStore view in the NSAppInstanceNSApp database enables you to view the subscriptions that have been created. In this case, the name of the view is based on the name of the event class that was created in the application definition file. You can see the query to view the subscribers for the example application in the following listing: View Subscriptions USE NSAppInstanceNSApp SELECT * FROM NSShipStoreView ORDER BY SubscriberId; Chapter 5: Developing with Notification Services 163 Deleting Subscriptions The following code shows how you can delete subscriptions that have been previously displayed in a ListBox. Like the previous example, the Notification Services Subscriber object provides the required method to work with the subscriber data. If ListBox1.SelectedIndex < 0 Then MsgBox("No subscriber has been selected.") Else ' Create the Instance object Dim myNSInstance As New NSInstance("NSAppInstance") ' Delete the Subscriber Dim oSubscriber As New Subscriber(myNSInstance) oSubscriber.SubscriberId = ListBox1.SelectedItem oSubscriber.Delete() ' Remove the entry from the list ListBox1.Items.Remove(ListBox1.SelectedItem) End If Firing the Data Event Using .NET Events are data that your notification application uses to generate notifications. The notification generation queries you write join event data and subscription data to produce notifications. The queries that generate notifications are fired during each generator quantum that has data to process. Event rules run in any quantum in which one or more event batches arrived. Scheduled rules run in any quantum that has scheduled subscriptions expected to be processed. You can see the screen that the example Notification Services client application uses to create Notification Services events in Figure 5-8. On the Event tab, the user can enter the store ID, the product ID, the product name, and the number of units shipped. In the earlier listing that created a subscription, you saw that a subscription was created for store ID 1. Therefore, if the user enters a value for store ID 1, then a Notification Services event will be created. Any other store ID values will not cause an event to fire. In the case of the sample application, no data validation is performed, so you need to enter data values for all of the fields. 164 Microsoft SQL Server 2005 Developer’s Guide Once all of the data has been entered, clicking the OK button will execute the code that you can see in the following listing: ' Create the Instance object Dim myNSInstance As New NSInstance("NSAppInstance") ' Create the Application object Dim myNSApp As New NSApplication(myNSInstance, "NSApp") Dim oEvent As New _ Microsoft.SqlServer.NotificationServices.Event( _ myNSApp, "ShipData") Dim oEventCollector As New EventCollector(myNSApp, "SQLData") ' Supply the event data oEvent("StoreId") = TextStore.Text oEvent("Date") = Now oEvent("ProductId") = TextProdID.Text oEvent("ProductName") = TextProdName.Text oEvent("Units") = TextUnits.Text oEventCollector.Write(oEvent) Dim iCountOfCommittedEvents As Integer = oEventCollector.Commit() Figure 5-8 The subscription application Chapter 5: Developing with Notification Services 165 At the top of this listing, you can see where the NSInstance and NSApplication objects are created. Next, a new Notification Services Event object named oEvent is created by passing an instance of the NSApp NSApplication object along with the value of “ShipData”, the name of the Notification Services event class, to the Event object’s constructor. The next section of code supplies the required event data. The values used for these field names must match the field values that compose the event class that was created in the application definition file. The ShipData event class used five fields. The StoreId is assigned the value that codes from the TextStore TextBox. The Date field is assigned the current date and time. The ProductID, ProductName, and Units fields are all assigned values from the TextBoxes that you saw earlier in Figure 5-6. After all of the field values have been assigned, the EventCollector Write method is used to write the events and the Commit method is used to send the events to the Notification Services application. Figure 5-9 shows the notification that was generated using the values you saw on Figure 5-8. The sample application used the WebBrowser object with the URL property pointed to the NSApplication.htm file to display the notification. It should be noted that for this sample application, the notification does not appear immediately. Instead, it is generated according to the schedule that was defined in the notification class section of the application definition file. The example uses a value of 60 seconds. Figure 5-9 Viewing the notification 166 Microsoft SQL Server 2005 Developer’s Guide If no notifications are generated, you can use the NSDiagnosticFailedNotifications stored procedure to begin troubleshooting the problem. You can see an example of running the NSDiagnosticFailedNotifications stored procedure in the following listing: View diagnostics USE NSAppInstanceNSMain EXEC NSDiagnosticFailedNotifications Firing the Data Event Using T-SQL The preceding example illustrated firing a Notification Services event using the NotificationServices API from a client application. However, you can also use T-SQL to generate events for your Notification Services application. The following listing illustrates calling the NSEventWriteShipData stored procedure to fire an event. The NSEventWriteShipData stored procedure is automatically created with your Notification Services application. Its actual name is based on the Event Class Name used in the ADF file. USE NSAppInstanceNSApp; Start an event batch DECLARE @BatchID bigint; EXEC dbo.NSEventBeginBatchShipData N'SQLData', @BatchID OUTPUT; EXEC dbo.NSEventWriteShipData @EventBatchId=@BatchID, @StoreID = 1, @Date='October 1, 2005', @ProductID = 31, @ProductName = "Item ThirtyOne", @Units=31 Flush event batch EXEC dbo.NSEventFlushBatchShipData @BatchID; The NSEventWriteShipData stored procedure is intended to be used for batch loading and requires a batch ID as its first parameter. Next, you need to supply the data required by the event that you defined in the application’s event class. In this example, you can see that a store ID of 1 is used to ensure that the event gets fired. You call the NSEventWriteShipData stored procedure for each event that you want to sent to the application. When all of the events have been sent, the NSEventFlush BatchShipData stored procedure is called to send the event data to the Notification Services application. Chapter 5: Developing with Notification Services 167 Summary Notification Services is a powerful new subsystem you can use as a basis for building your own notification applications. In this chapter you learned how to define a sample Notification Services application by creating the instance configuration file and application definition file as well as how to use the Notification Services API to add subscribers, subscriptions, and fire notification events. This page intentionally left blank . collection Figure 5-7 Adding a reference to the Notification Services library 160 Microsoft SQL Server 2005 Developer’s Guide For Each oSub As Subscriber In oSubscribers ' Add each Subscriber. DeliveryChannel property specifies the method by which the notification will 162 Microsoft SQL Server 2005 Developer’s Guide be generated. In this example, the notification will be created in. validation is performed, so you need to enter data values for all of the fields. 164 Microsoft SQL Server 2005 Developer’s Guide Once all of the data has been entered, clicking the OK button will