About SIF Events

An Event is a notification to subscribing agents that a data object has been added, changed, or deleted in the reporting application's database. In the Schools Interoperability Framework, any agent may report SIF_Event messages for any object, even if that agent is not the authoritative publisher of the object.

Subscribing to SIF Events

Agents that wish to receive SIF_Event messages must register with the zone integration server as a Subscriber of one or more SIF Data Object types. To subscribe to events for a specific object type, register a Subscriber message handler with Zone or Topic instances. When registering Subscribers with zones, repeatedly call the {@linkplain com.edustructures.sifworks.Zone#setSubscriber(Subscriber, ElementDef, int)} method for each SIF Data Object type you wish to subscribe to. When registering message handlers with Topics, call the {@linkplain com.edustructures.sifworks.Topic#setSubscriber(Subscriber, int)} method once to register with all zones bound to the topic (your Subscriber implementation will be called whenever a SIF_Event is received on any of the zones bound to that topic.) Be sure to specify the ADKFlags.PROV_SUBSCRIBE flag as the last parameter to these methods if you wish the ADK to send a SIF_Subscribe message to the zone when it connects.

When a SIF_Event message is received, it is dispatched to the appropriate Subscriber message handler's onEvent method for processing. Obtain a DataObjectInputStream from the Event instance by calling the Event parameter's {@linkplain com.edustructures.sifworks.Event#getData()} method, then repeatedly call the stream's {@linkplain com.edustructures.sifworks.DataObjectInputStream#readDataObject()} method to get the next SIFDataObject in the event payload.

For example,

CopyC#

public void OnEvent( Event evnt, IZone zone, IMessageInfo info )
{
   IDataObjectInputStream payload = evnt.Data;
   while( payload.Available ) 
   {
       StudentPersonal sp = (StudentPersonal)payload.ReadDataObject();
       switch( event.Action ) 
    {
           case EventAction.Add:
             // Add student...
             break;
           case EventActon.Change:
             // Change student...
             break;
           case EventAction.Delete:
             // Delete student...
             break;
       }
    }
}

If OnEvent returns successfully, the ADK acknowledges the SIF_Event message with a success SIF_Ack. If a SifException or other AdkException is thrown, the ADK acknowledges the SIF_Event with an error SIF_Ack using the error category, code, and description from the exception.