Mastering Oracle Apex: Raised User-Defined Exception for Start-Workflow Process Page

 declare
  l_message varchar2(4000);
begin
  l_message := 'Invalid input detected. Please review and correct the data.';
  raise_application_error(-20001, l_message);
end;

Raising the Exception in a Workflow Process

Now that you’ve declared the exception, it’s time to raise it in your workflow process page. Let’s assume you have a process that checks for invalid input data:

 declare
  l_input_data varchar2(100);
begin
  -- Validate input data
  if :P1_INPUT_DATA is null or :P1_INPUT_DATA = '' then
    raise_application_error(-20001, 'Invalid input detected. Please review and correct the data.');
  end if;
  
  -- Continue with the workflow process
  ...
end;

In this example, the exception is raised when the input data is null or empty. You can customize the condition to fit your specific requirements.

Handling the User-Defined Exception

When the exception is raised, Oracle Apex will display the custom error message to the user. But how do you handle the exception and provide a seamless user experience? Here are some tips:

Using the APEX_ERROR Package

The APEX_ERROR package provides a set of functions and procedures to handle and display error messages. You can use the APEX_ERROR.ADD_ERROR procedure to add the error message to the error stack:

 declare
  l_error_message varchar2(4000);
begin
  l_error_message := 'Invalid input detected. Please review and correct the data.';
  apex_error.add_error(
    p_message        => l_error_message,
    p_display_location => apex_error.c_inline_in_notification
  );
end;

Redirecting to an Error Page

Alternatively, you can redirect the user to a custom error page using the APEX_UTIL.REDIRECT_URL procedure:

 declare
  l_error_message varchar2(4000);
begin
  l_error_message := 'Invalid input detected. Please review and correct the data.';
  apex_util.redirect_url('f?p=&APP_ID.:ERROR_PAGE:&SESSION.');
end;

Best Practices for Handling User-Defined Exceptions

• Keep Error Messages Concise**: Ensure that your error messages are clear, concise, and easy to understand.
• Use APEX_ERROR Package**: Leverage the APEX_ERROR package to handle and display error messages consistently throughout your application.
• Test Thoroughly**: Test your user-defined exceptions extensively to ensure that they are raised correctly and handled elegantly.