raise_application_error exception handling in subprocedures - sql

Question

I have multiple stored procedures calling multiple stored procedures in my database. To give a small example, I've constructed a fictionalised version of a few of them below. In my example, a Java program calls calculate_bill, which calls calculate_commission, which calls update_record.
I'm hoping to get some advice on how best to propagate the error messages up the stack to the calling Java layer, so the user gets a precise error message corresponding to wherever the error has occurred.
I'm really quite stuck on this. I've played around in my example with raise_application_error and just continually shuffling it up the stack. Is the way I'm doing it below remotely correct? Or is one raise_application_error in the relevant procedure enough, with no pragma exception init etc needed?
To give an idea of what I mean, in the example below, if a user entered a number which corresponded to a record which couldn't be updated because it didn't exist, I'd like them to get the message:
"Error calculating bill. Error calculating commission. No record exists to be updated" or something to that effect.
So two questions:
What is the best practice, most efficient, most tidy way to pass error messages up the stack for the end user in the application layer?
Does anyone have any suggestions on tidier output from the code, i.e. the best way to concatenate these errors to make them more meaningful? I'm really open to any suggestions on how to make this work best as I have absolutely no prior experience in this.
Example:
(Error in code):
-20000 : Error in top level procedure
-20001 : Error in middle level procedure
-20002 : Error in bottom level procedure
Java code:
try {
// call calculate_bill
exception (SQLException ex)
// output oracle code and relevant message.
Oracle code:
create or replace procedure calculate_bill(in_num NUMBER)
is
error_calculating_commission EXCEPTION;
error_updating_record EXCEPTION;
PRAGMA EXCEPTION_INIT (error_calculating_commission, -20001);
PRAGMA EXCEPTION_INIT (error_updating_record , -20002);
begin
if in_num > 2 then
calculate_commission(in_num);
else
raise_application_error(-20000, 'Error calculating bill. ' || 'Record number doesn''t exist.', false);
end if;
exception
when error_calculating_commission then
raise_application_error(SQLCODE, 'Error calculating bill. ' || SQLERRM, false);
when error_updating_record then
raise_application_error(SQLCODE, 'Error calculating bill. ' || SQLERRM, false);
when others then
raise_application_error(-20000, 'Unknown error encountered calculating bill.', false);
end;
create or replace procedure calculate_commission(in_num NUMBER)
is
begin
if in_num < 30 then
raise_application_error(-20001, 'Number too small to calculate commission.', false);
elsif in_num >= 30 and < 40 then
declare
error_storing_record EXCEPTION;
PRAGMA EXCEPTION_INIT (error_storing_record , -20002);
begin
update_record(in_num);
exception
when error_storing_record then
raise_application_error(SQLCODE, 'Error calculating commission. ' || SQLERRM, false);
when others then
raise_application_error(-20001, 'Unknown error encountered calculating commission.', false);
else
raise_application_error(-20001, 'Number too large to calculate commission', false);
end if;
end;
create or replace procedure update_record(in_num NUMBER)
is
begin
//some SQL query with a where clause, where in_num equals something
exception
when no_data_found then
raise_application_error(-20002, 'No record exists to be updated', false);
when others then
raise_application_error(-20002, 'Unknown error encountered updating record.', false);
end if;
end;
Note: I know this example is a little contrived. I was just trying to keep it brief.

Answer 1

The way I would implement this is to use RAISE_APPLICATION_ERROR where the error actually originates, then leave it unhandled in the other layers (or, if you want to do logging in the database, catch it in the OTHERS section, then re-raise using RAISE rather than RAISE_APPLICATION_ERROR.
You're OTHERS sections are still perpetuating the problem raised in your previous question: when an unknown error occurs you're replacing it with a generic, unhelpful message. To paraphrase Tom Kyte, "a WHEN OTHERS that does not end in RAISE is a bug`.
With no logging in the database, I would re-write the provided code like this:
create or replace procedure calculate_bill(in_num NUMBER)
is
begin
if in_num > 2 then
calculate_commission(in_num);
else
raise_application_error(-20000, 'Error calculating bill. ' || 'Record number doesn''t exist.', false);
end if;
end;
create or replace procedure calculate_commission(in_num NUMBER)
is
begin
if in_num < 30 then
raise_application_error(-20001, 'Number too small to calculate commission.', false);
elsif in_num >= 30 and in_num < 40 then
update_record(in_num);
else
raise_application_error(-20001, 'Number too large to calculate commission', false);
end if;
end;
create or replace procedure update_record(in_num NUMBER)
is
v_stub number;
begin
select 1 into v_stub from dual where 1 = 0;
exception
when no_data_found then
raise_application_error(-20002, 'No record exists to be updated', false);
end;
Below is sample input and the stack traces they created:
exec calculate_bill(0)
ORA-20000: Error calculating bill. Record number doesn't exist.
ORA-06512: at "SCHEMANAME.CALCULATE_BILL", line 7
ORA-06512: at line 1
exec calculate_bill(10)
ORA-20001: Number too small to calculate commission.
ORA-06512: at "SCHEMANAME.CALCULATE_COMMISSION", line 5
ORA-06512: at "SCHEMANAME.CALCULATE_BILL", line 5
ORA-06512: at line 1
exec calculate_bill(35)
ORA-20002: No record exists to be updated
ORA-06512: at "SCHEMANAME.UPDATE_RECORD", line 8
ORA-06512: at "SCHEMANAME.CALCULATE_COMMISSION", line 7
ORA-06512: at "SCHEMANAME.CALCULATE_BILL", line 5
ORA-06512: at line 1
exec calculate_bill(100)
ORA-20001: Number too large to calculate commission
ORA-06512: at "SCHEMANAME.CALCULATE_COMMISSION", line 9
ORA-06512: at "SCHEMANAME.CALCULATE_BILL", line 5
ORA-06512: at line 1
If you were to add error logging to these procedures, it would be a simple matter of adding an OTHERS clause to the EXCEPTION sections:
WHEN OTHERS THEN
my_logging (SQLCODE, SQLERRM, DBMS_UTILITY.format_error_backtrace ());
RAISE;
The new exception created by your RAISE_APPLICATION_ERROR calls will be handled transparently by the RAISE.