Application Development with PAS for OpenEdge : Programming ABL Client Applications : Accessing client context regardless of application model
Accessing client context regardless of application model
OpenEdge supports the ClientContextId property on the Progress.Lang.OERequestInfo class that you can use to identify client context for both session-free and session-managed applications, especially in multi-tier application environments. OpenEdge provides instances of this class that you can reference using attributes of both the ABL client's server object handle and the PAS for OpenEdge session's SESSION system handle.
OpenEdge creates one instance of OERequestInfo when the client creates a server object handle and assigns the REQUEST-INFO attribute to the object reference. OpenEdge also initializes the ClientContextId property on this instance with a globally unique value that the client application can change, if necessary, before each remote request using the same server handle.
When the client makes a remote request on this server handle, the values of this property and other properties of OERequestInfo are sent to the PAS for OpenEdge session, where it initializes the same properties in a separate instance of OERequestInfo that is referenced by the CURRENT-REQUEST-INFO attribute on the session's SESSION handle. When the server session completes its handling of the request, it returns the OERequestInfo property values to the client that are set in the instance referenced by the CURRENT-RESPONSE-INFO attribute. Some of these values are different from those available through the CURRENT-REQUEST-INFO attribute, but the ClientContextId property value is the same unless your session code changes it prior to returning to the client.
When the remote request returns a response to the client, the client code can read the property values returned from the server in an OERequestInfo instance referenced by the RESPONSE-INFO attribute on the server object handle (or on the asynchronous request object handle returned for an asynchronous request).
For each subsequent client request on the same server handle, OpenEdge initializes the ClientContextId property on the REQUEST-INFO attribute instance from the ClientContextId value on the RESPONSE-INFO attribute, unless the client application changes the value prior to the request. In this way, a ClientContextId value can be propagated between the same client and PAS for OpenEdge instance with little or no code intervention.
Typically you use the client context identifier value set for the ClientContextId property to key a context store that is initialized at the start of a user login session and shared between the client and all servers that participate in the same login session. For more information on using the ClientContextId and other properties of the Progress.Lang.OERequestInfo class, especially on the server, see Managing client context for session-free and unbound session-managed connections. The following section describes use of these properties on the ABL client.
