<concept xml:lang="en" id="GUID-5AAE8371-E146-562B-B8AF-149FF981693C"><title>Observers and Notification</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>Messaging Framework provides two mixin interfaces, which define session observers and entry observers. </p> <ul><li id="GUID-8781CEE0-5C4C-5539-9691-6081747C8473"><p>The <xref href="GUID-BDE23754-4536-3AF7-8549-3B953F51167C.dita"><apiname>MMsvSessionObserver </apiname></xref> class is defined as a session observer is notified of events such as shutdown warnings, new message arrival, and registration of new MTMs. A class belonging to a message client application, such as the application UI class, must implement the interface to handle such events and take appropriate action. The client’s message server session object can also call the interface whenever it completes a request to the Message Server. </p> <p>Session observers are important for run-time extensibility of the Messaging architecture, as message client applications can be informed of new <xref href="GUID-E96D8052-0CB2-53A6-915F-133D3058DCF9.dita">MTMs being registered</xref>. As the registry classes are session observers, they also can update their lists of the available MTM components, allowing new components to be loaded. </p> </li> <li id="GUID-32DAABF3-F9C0-5981-9795-49A4592124E8"><p>The <xref href="GUID-B36289AC-769F-3A83-BADB-AE0568E97581.dita"><apiname>MMsvEntryObserver</apiname></xref> class is notified when an individual entry changes, or when access to a message store has been successfully gained. Client objects that need to observe a session view must implement this interface. </p> </li> </ul> </conbody></concept>