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For any given item type, you can define a single function that operates as both a selector and a callback function. A selector function is a PL/SQL procedure that automatically identifies the specific process definition to execute when a workflow is initiated for a particular item type but no process name is provided. Oracle Workflow also supports using a callback function to reset or test item type context information. You can define one PL/SQL procedure that includes both selector and callback functionality by following a standard API.

Oracle Workflow can call the selector/callback function with the following commands:

The standard API for the selector/callback function is as follows. This section is numbered with the notation 1-> for easy referencing. The numbers and arrows themselves are not part of the procedure.

1-> procedure <procedure name> (item_type in varchar2,
                                 item_key in varchar2,
                                 activity_id in number,
                                 command in varchar2,
                                 resultout in out varchar2) is

2-> <local declarations>

3-> begin
      if ( command = 'RUN' ) then
           <your RUN executable statements>
           resultout := '<Name of process to run>';
           return;
      end if;

4-> if ( command = 'SET_CTX' ) then
           <your executable statements for establishing context information>
           return;
      end if;

5-> if ( command = 'TEST_CTX' ) then
           <your executable statements for testing the validity of the current
                                                          context information>
           resultout := '<TRUE or FALSE> ';
           return;
      end if;

6-> if ( command = '<other command>' ) then
           resultout := ' ';
           return;
      end if;

7-> exception
           when others then
            WF_CORE.CONTEXT ('<package name>', '<procedure name>', <itemtype>,
                            <itemkey>, to_char(<actid>), <command>);
           raise;

8-> end <procedure name>;

1-> When the Workflow Engine calls the selector/callback function, it passes four parameters to the procedure and may expect a result when the procedure completes. The parameters are defined here:

2-> This section declares any local arguments that are used within the procedure.

3-> The procedure body begins in this section with an IF statement. This section contains one or more executable statements that make up your selector function. It executes if the value of command is 'RUN'. One of the executable statements should return a result for the procedure that reflects the process to run. For example, a result can be 'REQUISITION_APPROVAL', which is the name of a process activity.

4-> This section contains one or more executable statements that set item type context information if the value of command is 'SET_CTX'. The Workflow Engine calls the selector/callback function with this command each time it encounters a new item type and item key combination, before executing any function activities for that combination. This command is useful when you need to set item type context information in a database session before the activities in that session can execute as intended. For example, you might need to set up the responsibility and organization context for function activities that are sensitive to multi-organization data.

5-> This section contains one or more executable statements that validate item type context information if the value of command is 'TEST_CTX'. The Workflow Engine calls the selector/callback function with this command to validate that the current database session context is acceptable before the Workflow Engine executes an activity. For example, this callback functionality executes when the Notification Details web page is just about to launch a reference form. The code in this section should return 'TRUE' if the context is correct, and 'FALSE' if the context is incorrect. If the context is incorrect, you can raise an exception and place a message in the WF_CORE error system to indicate the reason the context is invalid. The raised exception is also printed in an error message in the form.

6-> This section handles execution modes other than 'RUN', 'SET_CTX' or 'TEST_CTX' as others may be added in the future. Since your function does not need to implement any of these other possible commands, it should simply return null.

7-> This section calls WF_CORE.CONTEXT( ) if an exception occurs, so that you can include context information in the error stack to help you locate the source of an error. See: CONTEXT, Oracle Workflow API Reference.

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