17Copyright © 2004, Oracle. All rights reserved.

Run Time Messages and Alerts

17-2 Copyright © 2004, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to do the following:

• Describe the default messaging behavior of a form

• Handle run-time failure of built-in subprograms

• Identify the different types of Forms messages

• Control system messages

• Create and control alerts

• Handle database server errors

17-3 Copyright © 2004, Oracle. All rights reserved.

Run-Time Messages and Alerts Overview

System Application

Alerts

Messages

InformativeError

WorkingApplication

17-5 Copyright © 2004, Oracle. All rights reserved.

Detecting Run-Time Errors

• FORM_SUCCESS– TRUE: Action successful– FALSE: Error/Fatal error occurred

• FORM_FAILURE– TRUE: A nonfatal error occurred– FALSE: Action successful or a fatal error occurred

• FORM_FATAL– TRUE: A fatal error occurred– FALSE: Action successful or a nonfatal error

occurred

17-7 Copyright © 2004, Oracle. All rights reserved.

Errors and Built-Ins

• Built-In failure does not cause an exception.

• Test built-in success with FORM_SUCCESS function.IF FORM_SUCCESS THEN . . .OR IF NOT FORM_SUCCESS THEN . . .

• What went wrong?– ERROR_CODE, ERROR_TEXT, ERROR_TYPE– MESSAGE_CODE, MESSAGE_TEXT, MESSAGE_TYPE

17-9 Copyright © 2004, Oracle. All rights reserved.

Message Severity Levels

>25

20

15

10

5

0

25

All (default)

More critical

Define by:

:SYSTEM.MESSAGE_LEVEL

17-11 Copyright © 2004, Oracle. All rights reserved.

Suppressing Messages

:SYSTEM.MESSAGE_LEVEL := ’5’;

UP;

IF NOT FORM_SUCCESS THEN

MESSAGE(’Already at the first Order’);

END IF;

:SYSTEM.MESSAGE_LEVEL := ’0’;

:SYSTEM.SUPPRESS_WORKING := ’TRUE’;

17-13 Copyright © 2004, Oracle. All rights reserved.

The FORM_TRIGGER_FAILURE Exception

BEGIN

--

RAISE form_trigger_failure;--

EXCEPTION--

WHEN <exception> THEN RAISE form_trigger_failure;--

Fail trigger

END;

17-15 Copyright © 2004, Oracle. All rights reserved.

Triggers for InterceptingSystem Messages

• On-Error:– Fires when a system error message is issued– Is used to trap Forms and Oracle Server errors, and

to customize error messages

• On-Message:– Fires when an informative system message is

issued– Is used to suppress or customize specific

messages

17-17 Copyright © 2004, Oracle. All rights reserved.

Handling Informative Messages

• On-Message trigger

• Built-in functions:– MESSAGE_CODE– MESSAGE_TEXT– MESSAGE_TYPE

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Setting Alert Properties

1

2

6543 7

Alert Styles:

Caution

Stop

Note

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Planning Alerts

Yes/Noquestions

Yes/No/Cancelquestions

Cautionmessages

Informativemessages

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Controlling Alerts

SET_ALERT_PROPERTY

SET_ALERT_BUTTON_PROPERTY

17-24 Copyright © 2004, Oracle. All rights reserved.

SHOW_ALERT Function

IF SHOW_ALERT(’del_Check’)=ALERT_BUTTON1 THEN

. . .

Alert_Button1Alert_Button2

Alert_Button3

17-26 Copyright © 2004, Oracle. All rights reserved.

Directing Errors to an Alert

PROCEDURE Alert_On_Failure IS

n NUMBER;

BEGIN

SET_ALERT_PROPERTY(’error_alert’,

ALERT_MESSAGE_TEXT,ERROR_TYPE||

’-’||TO_CHAR(ERROR_CODE)||

’: ’||ERROR_TEXT);

n := SHOW_ALERT(’error_alert’);

END;

17-27 Copyright © 2004, Oracle. All rights reserved.

Causes of Oracle Server Errors

Base table block

Implicit DML

Trigger/PU

Explicit DML

Stored PU call

Declarativeconstraint

Databasetrigger

Storedprogram unit

Form Oracle Server

17-29 Copyright © 2004, Oracle. All rights reserved.

Trapping Server Errors

Base table block

On-Error:DBMS_ERROR_CODEDBMS_ERROR_TEXT

Explicit DML/PU call

When Others:SQLCODESQLERRM

Constraint

DB trigger

Stored PU

Form Oracle Server

Predefinedmessage

RAISE_APPLICATION_

ERROR

RAISE_APPLICATION_

ERROR

17-30 Copyright © 2004, Oracle. All rights reserved.

Summary

In this lesson, you should have learned that:

• Forms displays messages at run time to inform the operator of events that occur in the session.

• You can use FORM_SUCCESS to test for run-time failure of built-ins.

• There are four types of Forms messages:– Informative– Error– Working– Application

17-31 Copyright © 2004, Oracle. All rights reserved.

Summary

• You can control system messages with built-ins and triggers:– MESSAGE_LEVEL– SUPPRESS_WORKING– On-[Error | Message] triggers– [ERROR | MESSAGE]_[CODE | TEXT | TYPE]

• Types of alerts: Stop, Caution, Note

• Alert built-ins:– SHOW_ALERT– SET_ALERT_PROPERTY– SET_ALERT_BUTTON_PROPERTY

17-32 Copyright © 2004, Oracle. All rights reserved.

Summary

• Handle database server errors:– Implicit DML: Use DBMS_ERROR_CODE and

DBMS_ERROR_TEXT in On-Error trigger– Explicit DML: Use SQLCODE and SQLERRM in WHEN

OTHERS exception handler

17-33 Copyright © 2004, Oracle. All rights reserved.

Practice 17 Overview

This practice covers the following topics:

• Using an alert to inform the operator that the customer’s credit limit has been exceeded

• Using a generic alert to ask the operator to confirm that the form should terminate