CUSTOM.pll

CUSTOM.pll is used to add extensions to Oracle's form Functionality. Some of the common scenario where CUSTOM.pll can be used are:-
1. Enabling/Disabling the fields
2. Changing the List of Values in a LOV field at runtime.
3. Defaulting values
4. Additional record level validations
5. Navigation to other screens.
6. Enabling Special Menu


Primarily there are two methods of extending Oracle Forms, and these are
    CUSTOM.pll
    FORMS Personalizations
In this article we will cover the basics of using CUSTOM.pll for extending Oracle Forms


How and why does CUSTOM.pll work?
Every form in Oracle Apps is created using something called as TEMPLATE.fmb. But some of the modules like HRMS have their own HR Specific Templates[HRTEMPLT.fmb]. These template files have form level triggers that make call to CUSTOM.pll. The triggers that can be trapped using CUSTOM.pll in HRMS screen can be different than those which can be trapped for other modules.


Commonly used events that are trapped using CUSTOM.pll are:-
   ZOOM
   WHEN-NEW-FORM-INSTANCE
   WHEN-NEW-BLOCK-INSTANCE
   WHEN-NEW-RECORD-INSTANCE
   WHEN-NEW-ITEM-INSTANCE
   WHEN-VALIDATE-RECORD


However, for example in HRMS, you can also write code in CUSTOM.pll to trap below listed events :-
PRE-DELETE and POST-DELETE
PRE-UPDATE and POST-UPDATE
PRE-INSERT and POST-INSERT
POST-FORMS-COMMIT
WHEN-CREATE-RECORD
KEY-DELREC




How to identify which trigger is most suitable for writing your business logic?
You can either open the FMB itself, and see the triggers which are calling CUSTOM.pll.
However, there is a easier way to work out the most suitable triggers. You can navigate to Help/Diagnostics/Custom Code/Show Custom Events


Once that radio button has been set, you will see the list of Events Displayed on the screen.



In some cases, the desired WHEN-NEW-BLOCK-INSTANCE or  WHEN-NEW-ITEM-INSTANCE are not being fired. What can I do?
It should always be possible to trap these events in CUSTOM.pll . But in some cases, the form  might have these triggers at block/field level, with the trigger property being OVERRIDE. Due to this, the corresponding form level triggers[ to invoke CUSTOM.pll] do not fire. In this case you must  raise a bug with Oracle on Metalink.


Structure code code in CUSTOM.pll
      IF event_name = 'WHEN-NEW-FORM-INSTANCE'
      THEN
         IF form_name = 'ARXTWMAI' AND block_name = 'INVOICE_HEADER'
         THEN
            xx_arxtwmai.default_customer;
         ELSIF form_name = 'ARXTWMAI' AND block_name = 'INVOICE_HEADER'
         THEN
                .....
         END IF;
       ELSIF event_name = 'WHEN-NEW-BLOCK-INSTANCE'
      THEN
                .....
      END IF ;



Lets take some scenario's where CUSTOM.pll can be used
1. Change the label of a field
app_item_property2.set_property ('BLOCK.FIELD',label,'New Label');

2. Default a value
copy (TO_CHAR (n_person_id),'PERSON_BLOCK.PERSON_ID' );

3. Alter the SQL for LOV Query
PROCEDURE filter_customers_in_lov IS
  v_customer_group_id recordgroup;
  n_temp_id           NUMBER;
  v_customer_lov      lov;
BEGIN
  v_customer_group_id := create_group_from_query('XX_CUSTOMER_GROUP'
                                   ,'select ... from hz_cust_accounts where ..your custom criteria here..');
  n_temp_id           := populate_group(v_customer_group_id);
  v_customer_lov    := find_lov('EXISTING_LOV_NAME_HERE');
  IF get_lov_property(v_customer_lov,group_name) = 'EXISTING_GROUP_NAME_HERE'
  THEN
         set_lov_property(v_customer_lov,group_name,'XX_CUSTOMER_GROUP');
  END IF;
END filter_customers_in_lov;


4. Make a field mandatory
app_item_property2.set_property ('XXBLOCK_NAME.XXFIELD_NAME',required,property_true);
Similarly you can enable or disable the fields too.

5. You can display messages, for example
FND_MESSAGE.CLEAR;
fnd_message.set_name('APPL_SHORT_NAME_HERE', 'MSG_NAME_HERE'); or fnd_message.set_string('message text');
fnd_message.warn or fnd_message.error or fnd_message.


6. Enable or Disable Special Menu
PROCEDURE manage_special_menu IS
  mi_id menuitem;
BEGIN
  mi_id := find_menu_item('SPECIAL.SPECIAL15');
  IF name_in('system.cursor_block') = 'INVOICE_HEADER' THEN
    app_special2.instantiate('SPECIAL15', 'Print Invoice');
    set_menu_item_property(mi_id, displayed, property_true);
    set_menu_item_property(mi_id, enabled, property_true);
  ELSE
    set_menu_item_property(mi_id, displayed, property_false);
  END IF;
END manage_special_menu;


7. Handle the click on Special Menu
  IF event_name = 'SPECIAL15' THEN
    IF form_name = 'INVOICE_FORM' THEN
      xx_invoice_form.process_printing;
    END IF;
    IF form_name = 'SUPPLIER_FORM' THEN
      xx_supplier_form.email_supplier;
    END IF;
  END IF;


8. Ask user a question, and take appropriate action  v_token_value      VARCHAR2(1000);
  n_button_selection INTEGER;
BEGIN
  fnd_message.set_name('APPL', 'MESSAGE');
  fnd_message.set_token('XXTOKEN1', v_token_value);
  n_button_selection := fnd_message.question('Email Invoice', 'Fax Invoice', '', 1, 2, 'question');
  IF n_button_selection = 1 THEN
    xx_call_invoice_print;
  ELSE
    xx_fax_invoice;
  END IF;

9. Call Another form functionfnd_function.EXECUTE(
   function_name => 'XX_FORM_FUNCTION_NAME_HERE'
  ,open_flag        => 'Y'
  ,session_flag     => 'SESSION'
  ,other_params   => 'P_INVOICE_ID = "' || n_invoice_header_id || '"'
  ,activate_flag    => 'Y');


10. Make some segments of a KeyFlexfield Display-Only depending upon some conditionFor example to make 1st segment of a KFF display-only, we can use
IF v_check_result='xyz' THEN
FND_KEY_FLEX.UPDATE_DEFINITION(
     BLOCK => 'BLOCKNAMEHERE'
    ,FIELD => 'FLEXFIELDNAME'
   ,ENABLED => 'Y'
   ,DISPLAYABLE => 1);
END IF ;


As you may have gathered by now, almost any form related task can be done using CUSTOM.pll

Action Type in CUSTOM	Allowed
Opening SQL Cursors	Yes
Executing pl/sql stored procedures	Yes
Referencing fields using bind notation like :block.field	No
Exception management	Yes

For additional reading on CUSTOM.pll, please visit
Best Practices for Development on CUSTOM.pll
Playing with CUSTOM.pll