Real-Time Incremental Feeds

Creating real-time incremental feeds also requires additional steps. You must complete the following tasks when creating real-time incremental feeds:

1. Define the DSPARAMETER_INCREMENTAL data source parameter found in the PTFP_FEED:UTILITY:Utility application class and set it to an appropriate value in your implementation of the processSettingsChange method for your data source :

   &thisDSP = %This.addParameter(&utility.DSPARAMETER_INCREMENTAL, ⇒
   String(&utility.INCREMENTALOPTION_NO));
   &thisDSP.Name = &thisDSP.ID;
   &thisDSP.Description = MsgGetText(219, 3008, "Message Not Found - Incremental");
   &thisDSP.FieldType = &utility.FIELDTYPE_SIGNEDNUMBER;
   &thisDSP.DefaultValue = String(&utility.INCREMENTALOPTION_NO);
   &thisDSP.Value = &thisDSP.DefaultValue;
   &thisDSP.Required = True;
   

   Important:

   The incremental feed option is incompatible with the paged feed option. Do not allow both options to be set simultaneously.

2. Modify the associated advanced feed options page to allow feed administrators the ability to set this option.

3. Generate delta feed entries in your implementation of the execute method for your data source based on the QUERYPARAMETER_IFMODIFIEDSINCE query parameter of the PTFP_FEED:UTILITY:Utility application class.

   Your implementation of the execute method must contain both the QUERYPARAMETER_IFNONEMATCH and the QUERYPARAMETER_IFMODIFIEDSINCE query parameters. QUERYPARAMETER_IFNONEMATCH is the feed ID and QUERYPARAMETER_IFMODIFIEDSINCE is the time at which the feed was last requested.

   The following code excerpt shows how to get the QUERYPARAMETER_IFNONEMATCH and QUERYPARAMETER_IFMODIFIEDSINCE query parameters using RequestInfo in the execute method of the data source:

   Local PTFP_FEED:DataSource:DataSourceParameter &thisDSP;
   Local string &ifNoneMatch, &ifModifiedSince, &select;
   Local datetime &lastmodified_dt = DateTime6(1900, 1, 1, 0, 0, 0);
   Local boolean &incremental;
   
   /* Get the Incremental Parameter */
   &thisDSP = %This.getParameterById(&utility.DSPARAMETER_INCREMENTAL);
   If &thisDSP <> Null And
   (&thisDSP.EvaluatedValue = String(&utility.INCREMENTALOPTION_YES)) Then
      &incremental = True;
   Else
      &incremental = False;
   End-If;
   
   &ifNoneMatch = &utility.RequestInfo.getParameter(&utility.QUERYPARAMETER_⇒
   IFNONEMATCH);
   &ifModifiedSince = &utility.RequestInfo.getParameter(&utility.QUERYPARAMETER_⇒
   IFMODIFIEDSINCE);
   If All(&ifModifiedSince) Then
      &lastmodified_dt = &utility.httpStringToDatetime(&ifModifiedSince);
   End-If;
   /* Compare and verify that &ifNoneMatch is same as the feed ID            */ 
   
   /* Compare the &lastmodified_dt with appropriate datetime column like the */
   /* LASTUPDDTTM field in the record used for generating the feed entries   */
   

4. When the execute method of a data source returns no feed entries, the Feed Publishing Framework issues a 304-Not Modified HTTP header. If you are using a custom feed handler—that is, a service operation different from the PTFP_GETFEED service operation —then use the setMessageHeadersAndMimeType method to set HTTP conditional headers.

   For example:

   method OnRequest
      /+ &pRequestMsg as Message +/
      /+ Returns Message +/
      /+ Extends/implements PS_PT:Integration:IRequestHandler.OnRequest +/
      Local Message &responseMsg;
      Local XmlDoc &xmlDoc;
      Local string &temp, &errorText;
      Local PTFP_FEED:UTILITY:Utility &utility = &feedFactory_inst.Utility;
      Local PTFP_FEED:XML_FEED:FeedDoc &feedDoc;
      Local PTFP_FEED:UTILITY:FeedRequest &request;
   
      /* Ccreate the Search Request object */
      &request = create PTFP_FEED:UTILITY:FeedRequest("FeedRequest");
      ...
      try
         &feedDoc = &feedFactory_inst.getFeedDoc(&request);
      catch PTFP_FEED:EXCEPTION:NotFoundException &ex1
         &errorText = MsgGetExplainText(219, 3112, "(Message not found) Not Found");
      catch PTFP_FEED:EXCEPTION:PrivilegeException &ex2
         &errorText = MsgGetExplainText(219, 3113, "(Message not found) ⇒
   Not Authorized");
      catch PTFP_FEED:EXCEPTION:FeedException &ex3
         &errorText = &utility.getExceptionText(&ex3);
      end-try;
      /* Create the response message */
      &responseMsg = CreateMessage(Operation.PTFP_GETFEED, %IntBroker_Response);
      If None(&errorText) Then
         &responseMsg = &utility.setMessageHeadersAndMimeType(&responseMsg, ⇒
   &feedDoc, &request);
      Else
         &temp = "<?xml version='1.0' encoding='UTF-8'?><ErrorMessage>" | ⇒
   &errorText | "</ErrorMessage>";
         &xmlDoc = CreateXmlDoc(&temp);
         &responseMsg.SetXmlDoc(&xmlDoc);
         &responseMsg.SegmentContentType = &utility.MIMETYPE_XML;
      End-If;
      Return &responseMsg;
   end-method;