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A default callback function can be called at various points by the actions of the WF_NOTIFICATION APIs. You may provide your own custom callback function, but it must follow standard specifications.

If you do not need to handle attributes of type event through your callback function, the procedure must use the following standard API:

procedure <name in callback argument>

(command in varchar2,
      context in varchar2,
      attr_name in varchar2,
      attr_type in varchar2,
      text_value in out varchar2,
      number_value in out number,
      date_value in out date);

If the callback function does need to handle attributes of type event, you can overload the procedure name with a second implementation that includes an additional argument for the event value. In this case you should also retain the original implementation for backward compatibility. However, it is recommended that you do not overload the procedure unless you have a requirement to handle event attributes.

The implementation of the procedure for event values must use the following standard API:

procedure <name in callback argument>

(command in varchar2,
      context in varchar2,
      attr_name in varchar2,
      attr_type in varchar2,
      text_value in out varchar2,
      number_value in out number,
      date_value in out date
      event_value in out nocopy wf_event_t);

For ease of maintenance, you can define the procedure that does not include the event_value argument to call the procedure that does include that argument, so that you only need to maintain one version of your code. The following example shows one way to implement such a call:

procedure your_callback

(command in varchar2,
      context in varchar2,
      attr_name in varchar2,
      attr_type in varchar2,
      text_value in out varchar2,
      number_value in out number,
      date_value in out date)

is
  event_value wf_event_t;

begin
  your_package.your_callback(command, context, attr_name,
                           attr_type, text_value,
                          number_value, date_value,
                          event_value);

exception
  when others then
    Wf_Core.Context('your_package', 'your_callback',
                 command, context, attr_name, attr_type,
                 ':'||text_value||':'||to_char(number_value)
                 ||':'||to_char(date_value)||':');
    raise;

end your_callback;

Arguments (input)

Note: The arguments text_value, number_value, and date_value, as well as event_value if you are using this argument, are mutually exclusive. That is, you should use only one of these arguments, depending on the value of the attr_type argument.

When a notification is sent, the system calls the specified callback function once for each SEND attribute (to get the attribute value).

Example 1

For each SEND attribute, call:

 your_callback('GET', context, 'BUGNO', 'NUMBER', textval, numval, dateval);

Example 2

When the user responds to the notification, the callback is called again, once for each RESPOND attribute.

 your_callback('SET', context, 'STATUS', 'TEXT', 'COMPLETE', numval, dateval);

Example 3

Then finally the Notification System calls the 'COMPLETE' command to indicate the response is complete.

 your_callback('COMPLETE', context, attrname, attrtype, textval, numval, dateval);

Example 4

For a SEND attribute of type event, call the implementation that includes the event_value argument.

 your_callback('GET', context, 'RECEIVE_EVENT', 'EVENT', textval, numval, dateval, eventval);

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