Exception handling - general concepts
ok, well i skipped the chapter on exception handling :=)
Correct me if im wrong, but lets say im writing some code and im not sure how to handle some of the exceptions that might get thrown or what exceptions will get thrown for that matter. How does one go about handling every possible exception that is "required".
I guess what im trying to ask is that if a certain block of code is calling methods that throw specific exceptions, then you will need to handle those exceptions. So that means you need to be aware of, or know to go lookup the possible exceptions that those methods can throw.
Im skipping around in Beginning Java 2, from wronx press jdk 1.4 edition
This is quite a hard one to be specific on as I think most of us learned this with a bit of trial and error.
1. IO always requires the method to be thrown ie
public void writeContents() throws IOException {
// methods
2. The compiler will tell you when you need a try /catch block
3. I often code this with;-
try {
// my methods here;
catch (Exception ignore) {}
and have empty braces with a general catch all Exception on the first run
4. Then if there are problems such as the code won't work I fill in the blanks ie;-
catch (Exception e) {System.out.println(e);}
// or e.getMessage() );
// or printStackTrace();
depending on what the first message is
5. Correct the exception now that you know what it is. Really this is a form of 'divide and conquer' as you eliminate the problems as they occur through javas exception handling abilities.
6. With a bit more practice you will implement things like finally and know when to put the handler back to 'catch (Exception ignore) {}' and when to leave it in.
7. Exception handling can also be used to instruct the client in useful ways too eg;-
try {
myTextfield.setText("Enter Your Age");
myInt = parse ...(myTextfield.getText(etc ...
catch (NumberFormatException nfe) {
myTextfield.setText("Enter Number Values Only");
// or something like
catch (NullPointerException nfe) {
myTextfield.setText("Oops you forgot to enter a value");
This has been my experience anyway + I trust I have assisted
Similar Messages
-
Hello. In my applications I usually have a try catch(Throwable) block surrounding all the top code (the code in main()) to log and report errors and exceptions that is not caught anywhere else, and to have my application exit in a controlled way. But I recently noticed that exceptions thrown in event handling (i.e. java.awt.EventDispatchThread.run) are not caught by the try catch block in main().
Are there any easy way to catch everything so my app can exit in a controlled way?
If this is not possible which exceptions are not propagated to main()? I would guess that it's exceptions thrown in other threads, is this correct? If so, do I have to surround all event handling by try catch(Throwable) to be safe?
I would like more information and guidelines about exception handling. Any book recommendations?
Help appreciated, thanks!You should never let exceptions propagate outside your event handling methods.
If you don't follow that rule, the java.awt.EventDispatchThread.run() method terminates and the Java Virtual Machine tries to print the stack trace to the terminal window (if there is one) and then exits, but not through your main() method.
So, try /catch all Exceptions inside your event handler methods:
// inside event handler method
try {
// handle event here
} catch (Throwable t) {
// handle errors and recover from errors here
// and either log error or if important display message to the user.
}There is no easy-lazy way to do exception handling by only having the try/catch block in main in this case.
Note : If any of the listeners throws an exception none of the following listeners is called. Since there is no guarantee of the order in which listeners are called you cannot be sure which ones are called first. -
Exception Handling Concept Gone Bad!!
Okay, this is by far the most embarrassing hack of code I've done thus far . . . but it works. I am trying to run a select where if there is no data or null returned, place it into the value "v_pidm', and then let the action occur. Simple enough, right? Wrong! A select that return no data which is using a 'into' function is an exception . . . "no data found." Oracle sends this to the exception block as it should. Okay, I don't want to stop and start my script a million times, there I added an sub Begin/End with an exception to handle the say error and perform an insert. I know you shouldn't use an exception state for inserts another than capturing errors . . . you know bad practices and all. Any ideas as how to better handle the select statement that should regularly return no data? I was thinking about some along the line of nvl(v_pidm, 0) or something, but I am getting errors.
set serveroutput ON SIZE 1000000
set heading off
set feedback off
set trimspool off
set echo off
set pagesize 0
set termout on
Declare
error varchar(255);
v_pidm number(8);
Begin
Begin
select distinct saraatt_pidm
into
v_pidm
from saraatt, saradap
where saraatt_appl_no = SARADAP_APPL_NO
and saraatt_term_code = SARADAP_TERM_CODE_ENTRY
and saraatt_pidm = 4;
Exception
when too_many_rows then
error := SQLERRM;
DBMS_OUTPUT.PUT_LINE(' %% Oracle Error! %% The select statement returned more than two rows ');
when no_data_found then
error := SQLERRM;
DBMS_OUTPUT.PUT_LINE('Select Returned No Data . . . Therefore Insert new record for ' || v_pidm );
v_pidm := -999;
when others then
error := SQLERRM;
DBMS_OUTPUT.PUT_LINE(' %% Oracle Error! %% An Error Occured ' || substr(error,5,20));
End;
DBMS_OUTPUT.PUT_LINE('Pidm: ' || v_pidm);
End;it would be better to just let the exception get propagated up so that you can see the full error stack.
Agrees fully with Justin
@Pr****
It took me a while as well, but in the end the best thing to do is avoid a WHEN OTHERS at all cost.
Once you resort to it, you're actually hiding some flaw(s), it might be design (it usually is)....or whatever, and the database covers up for t, and gets the blame.
And it's a pet-peeve of Tom Kyte for quite a while, and he wrote very good articles on it, do some readng on them:
http://google.com/search?q=site%3Atkyte.blogspot.com+%22when+others%22
Okay, I don't want to stop and start my script a million times, there I added an sub Begin/End with an exception to handle the say error and perform an insertYour example also doesn't seem to show the complete picture then?
I see no INSERT statement?
You have hidden your complete block structure, which makes it hard to guess what's going on/help you.
Perhaps you've nested your example in real life in another block, having it's own exception handler and so on...
I am getting errors.If you're getting errors and want some volunteers to help, then why not just post the full error message as well?
And your database version (the result of: select * from v$version; ) -
PL/SQL 101 : Exception Handling
Frequently I see questions and issues around the use of Exception/Error Handling in PL/SQL. More often than not the issue comes from the questioners misunderstanding about how PL/SQL is constructed and executed, so I thought I'd write a small article covering the key concepts to give a clear picture of how it all hangs together. (Note: the examples are just showing examples of the exception handling structure, and should not be taken as truly valid code for ways of handling things)
Exception Handling
Contents
1. Understanding Execution Blocks (part 1)
2. Execution of the Execution Block
3. Exceptions
4. Understanding Execution Blocks (part 2)
5. How to continue exection of statements after an exception
6. User defined exceptions
7. Line number of exception
8. Exceptions within code within the exception block
1. Understanding Execution Blocks (part 1)
The first thing that one needs to understand is almost taking us back to the basics of PL/SQL... how a PL/SQL execution block is constructed.
Essentially an execution block is made of 3 sections...
+---------------------------+
| Declaration Section |
+---------------------------+
| Statements Section |
+---------------------------+
| Exception Section |
+---------------------------+
The Declaration section is the part defined between the PROCEDURE/FUNCTION header or the DECLARE keyword (for anonymous blocks) and the BEGIN keyword. (Optional section)
The Statements section is where your code goes and lies between the BEGIN keyword and the EXCEPTION keyword (or END keyword if there is no EXCEPTION section). (Mandatory section)
The Exception section is where any exception handling goes and lies between the EXCEPTION keyword at the END keyword. (Optional section)
Example of an anonymous block...
DECLARE
.. declarative statements go here ..
BEGIN
.. code statements go here ..
EXCEPTION
.. exception handlers go here ..
END;
Example of a procedure/function block...
[CREATE OR REPLACE] (PROCEDURE|FUNCTION) <proc or fn name> [(<parameters>)] [RETURN <datatype>] (IS|AS)
.. declarative statements go here ..
BEGIN
.. code statements go here ..
EXCEPTION
.. exception handlers go here ..
END;
(Note: The same can also be done for packages, but let's keep it simple)
2. Execution of the Execution Block
This may seem a simple concept, but it's surprising how many people have issues showing they haven't grasped it. When an Execution block is entered, the declaration section is processed, creating a scope of variables, types , cursors, etc. to be visible to the execution block and then execution enters into the Statements section. Each statment in the statements section is executed in turn and when the execution completes the last statment the execution block is exited back to whatever called it.
3. Exceptions
Exceptions generally happen during the execution of statements in the Statements section. When an exception happens the execution of statements jumps immediately into the exception section. In this section we can specify what exceptions we wish to 'capture' or 'trap' and do one of the two following things...
(Note: The exception section still has access to all the declared items in the declaration section)
3.i) Handle the exception
We do this when we recognise what the exception is (most likely it's something we expect to happen) and we have a means of dealing with it so that our application can continue on.
Example...
(without the exception handler the exception is passed back to the calling code, in this case SQL*Plus)
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_name VARCHAR2(20);
3 begin
4 select ename
5 into v_name
6 from emp
7 where empno = &empno;
8 dbms_output.put_line(v_name);
9* end;
SQL> /
Enter value for empno: 123
old 7: where empno = &empno;
new 7: where empno = 123;
declare
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 4
(with an exception handler, we capture the exception, handle it how we want to, and the calling code is happy that there is no error for it to report)
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_name VARCHAR2(20);
3 begin
4 select ename
5 into v_name
6 from emp
7 where empno = &empno;
8 dbms_output.put_line(v_name);
9 exception
10 when no_data_found then
11 dbms_output.put_line('There is no employee with this employee number.');
12* end;
SQL> /
Enter value for empno: 123
old 7: where empno = &empno;
new 7: where empno = 123;
There is no employee with this employee number.
PL/SQL procedure successfully completed.
3.ii) Raise the exception
We do this when:-
a) we recognise the exception, handle it but still want to let the calling code know that it happened
b) we recognise the exception, wish to log it happened and then let the calling code deal with it
c) we don't recognise the exception and we want the calling code to deal with it
Example of b)
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_name VARCHAR2(20);
3 v_empno NUMBER := &empno;
4 begin
5 select ename
6 into v_name
7 from emp
8 where empno = v_empno;
9 dbms_output.put_line(v_name);
10 EXCEPTION
11 WHEN no_data_found THEN
12 INSERT INTO sql_errors (txt)
13 VALUES ('Search for '||v_empno||' failed.');
14 COMMIT;
15 RAISE;
16* end;
SQL> /
Enter value for empno: 123
old 3: v_empno NUMBER := &empno;
new 3: v_empno NUMBER := 123;
declare
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at line 15
SQL> select * from sql_errors;
TXT
Search for 123 failed.
SQL>
Example of c)
SQL> ed
Wrote file afiedt.buf
1 declare
2 v_name VARCHAR2(20);
3 v_empno NUMBER := &empno;
4 begin
5 select ename
6 into v_name
7 from emp
8 where empno = v_empno;
9 dbms_output.put_line(v_name);
10 EXCEPTION
11 WHEN no_data_found THEN
12 INSERT INTO sql_errors (txt)
13 VALUES ('Search for '||v_empno||' failed.');
14 COMMIT;
15 RAISE;
16 WHEN others THEN
17 RAISE;
18* end;
SQL> /
Enter value for empno: 'ABC'
old 3: v_empno NUMBER := &empno;
new 3: v_empno NUMBER := 'ABC';
declare
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
ORA-06512: at line 3
SQL> select * from sql_errors;
TXT
Search for 123 failed.
SQL>
As you can see from the sql_errors log table, no log was written so the WHEN others exception was the exception that raised the error to the calling code (SQL*Plus)
4. Understanding Execution Blocks (part 2)
Ok, so now we understand the very basics of an execution block and what happens when an exception happens. Let's take it a step further...
Execution blocks are not just a single simple block in most cases. Often, during our statements section we have a need to call some reusable code and we do that by calling a procedure or function. Effectively this nests the procedure or function's code as another execution block within the current statement section so, in terms of execution, we end up with something like...
+---------------------------------+
| Declaration Section |
+---------------------------------+
| Statements Section |
| . |
| +---------------------------+ |
| | Declaration Section | |
| +---------------------------+ |
| | Statements Section | |
| +---------------------------+ |
| | Exception Section | |
| +---------------------------+ |
| . |
+---------------------------------+
| Exception Section |
+---------------------------------+
Example... (Note: log_trace just writes some text to a table for tracing)
SQL> create or replace procedure a as
2 v_dummy NUMBER := log_trace('Procedure A''s Declaration Section');
3 begin
4 v_dummy := log_trace('Procedure A''s Statement Section');
5 v_dummy := 1/0; -- cause an exception
6 exception
7 when others then
8 v_dummy := log_trace('Procedure A''s Exception Section');
9 raise;
10 end;
11 /
Procedure created.
SQL> create or replace procedure b as
2 v_dummy NUMBER := log_trace('Procedure B''s Declaration Section');
3 begin
4 v_dummy := log_trace('Procedure B''s Statement Section');
5 a; -- HERE the execution passes to the declare/statement/exception sections of A
6 exception
7 when others then
8 v_dummy := log_trace('Procedure B''s Exception Section');
9 raise;
10 end;
11 /
Procedure created.
SQL> exec b;
BEGIN b; END;
ERROR at line 1:
ORA-01476: divisor is equal to zero
ORA-06512: at "SCOTT.B", line 9
ORA-06512: at line 1
SQL> select * from code_trace;
TXT
Procedure B's Declaration Section
Procedure B's Statement Section
Procedure A's Declaration Section
Procedure A's Statement Section
Procedure A's Exception Section
Procedure B's Exception Section
6 rows selected.
SQL>
Likewise, execution blocks can be nested deeper and deeper.
5. How to continue exection of statements after an exception
One of the common questions asked is how to return execution to the statement after the one that created the exception and continue on.
Well, firstly, you can only do this for statements you expect to raise an exception, such as when you want to check if there is no data found in a query.
If you consider what's been shown above you could put any statement you expect to cause an exception inside it's own procedure or function with it's own exception section to handle the exception without raising it back to the calling code. However, the nature of procedures and functions is really to provide a means of re-using code, so if it's a statement you only use once it seems a little silly to go creating individual procedures for these.
Instead, you nest execution blocks directly, to give the same result as shown in the diagram at the start of part 4 of this article.
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure b (p_empno IN VARCHAR2) as
2 v_dummy NUMBER := log_trace('Procedure B''s Declaration Section');
3 begin
4 v_dummy := log_trace('Procedure B''s Statement Section');
5 -- Here we start another execution block nested in the first one...
6 declare
7 v_dummy NUMBER := log_trace('Nested Block Declaration Section');
8 begin
9 v_dummy := log_trace('Nested Block Statement Section');
10 select empno
11 into v_dummy
12 from emp
13 where empno = p_empno; -- Note: the parameters and variables from
parent execution block are available to use!
14 exception
15 when no_data_found then
16 -- This is an exception we can handle so we don't raise it
17 v_dummy := log_trace('No employee was found');
18 v_dummy := log_trace('Nested Block Exception Section - Exception Handled');
19 when others then
20 -- Other exceptions we can't handle so we raise them
21 v_dummy := log_trace('Nested Block Exception Section - Exception Raised');
22 raise;
23 end;
24 -- ...Here endeth the nested execution block
25 -- As the nested block handled it's exception we come back to here...
26 v_dummy := log_trace('Procedure B''s Statement Section Continued');
27 exception
28 when others then
29 -- We'll only get to here if an unhandled exception was raised
30 -- either in the nested block or in procedure b's statement section
31 v_dummy := log_trace('Procedure B''s Exception Section');
32 raise;
33* end;
SQL> /
Procedure created.
SQL> exec b(123);
PL/SQL procedure successfully completed.
SQL> select * from code_trace;
TXT
Procedure B's Declaration Section
Procedure B's Statement Section
Nested Block Declaration Section
Nested Block Statement Section
No employee was found
Nested Block Exception Section - Exception Handled
Procedure B's Statement Section Continued
7 rows selected.
SQL> truncate table code_trace;
Table truncated.
SQL> exec b('ABC');
BEGIN b('ABC'); END;
ERROR at line 1:
ORA-01722: invalid number
ORA-06512: at "SCOTT.B", line 32
ORA-06512: at line 1
SQL> select * from code_trace;
TXT
Procedure B's Declaration Section
Procedure B's Statement Section
Nested Block Declaration Section
Nested Block Statement Section
Nested Block Exception Section - Exception Raised
Procedure B's Exception Section
6 rows selected.
SQL>
You can see from this that, very simply, the code that we expected may have an exception was able to either handle the exception and return to the outer execution block to continue execution, or if an unexpected exception occurred then it was able to be raised up to the outer exception section.
6. User defined exceptions
There are three sorts of 'User Defined' exceptions. There are logical situations (e.g. business logic) where, for example, certain criteria are not met to complete a task, and there are existing Oracle errors that you wish to give a name to in order to capture them in the exception section. The third is raising your own exception messages with our own exception numbers. Let's look at the first one...
Let's say I have tables which detail stock availablility and reorder levels...
SQL> select * from reorder_level;
ITEM_ID STOCK_LEVEL
1 20
2 20
3 10
4 2
5 2
SQL> select * from stock;
ITEM_ID ITEM_DESC STOCK_LEVEL
1 Pencils 10
2 Pens 2
3 Notepads 25
4 Stapler 5
5 Hole Punch 3
SQL>
Now, our Business has told the administrative clerk to check stock levels and re-order anything that is below the re-order level, but not to hold stock of more than 4 times the re-order level for any particular item. As an IT department we've been asked to put together an application that will automatically produce the re-order documents upon the clerks request and, because our company is so tight-ar*ed about money, they don't want to waste any paper with incorrect printouts so we have to ensure the clerk can't order things they shouldn't.
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure re_order(p_item_id NUMBER, p_quantity NUMBER) is
2 cursor cur_stock_reorder is
3 select s.stock_level
4 ,r.stock_level as reorder_level
5 ,(r.stock_level*4) as reorder_limit
6 from stock s join reorder_level r on (s.item_id = r.item_id)
7 where s.item_id = p_item_id;
8 --
9 v_stock cur_stock_reorder%ROWTYPE;
10 begin
11 OPEN cur_stock_reorder;
12 FETCH cur_stock_reorder INTO v_stock;
13 IF cur_stock_reorder%NOTFOUND THEN
14 RAISE no_data_found;
15 END IF;
16 CLOSE cur_stock_reorder;
17 --
18 IF v_stock.stock_level >= v_stock.reorder_level THEN
19 -- Stock is not low enough to warrant an order
20 DBMS_OUTPUT.PUT_LINE('Stock has not reached re-order level yet!');
21 ELSE
22 IF v_stock.stock_level + p_quantity > v_stock.reorder_limit THEN
23 -- Required amount is over-ordering
24 DBMS_OUTPUT.PUT_LINE('Quantity specified is too much. Max for this item: '
||to_char(v_stock.reorder_limit-v_stock.stock_level));
25 ELSE
26 DBMS_OUTPUT.PUT_LINE('Order OK. Printing Order...');
27 -- Here goes our code to print the order
28 END IF;
29 END IF;
30 --
31 exception
32 WHEN no_data_found THEN
33 CLOSE cur_stock_reorder;
34 DBMS_OUTPUT.PUT_LINE('Invalid Item ID.');
35* end;
SQL> /
Procedure created.
SQL> exec re_order(10,100);
Invalid Item ID.
PL/SQL procedure successfully completed.
SQL> exec re_order(3,40);
Stock has not reached re-order level yet!
PL/SQL procedure successfully completed.
SQL> exec re_order(1,100);
Quantity specified is too much. Max for this item: 70
PL/SQL procedure successfully completed.
SQL> exec re_order(2,50);
Order OK. Printing Order...
PL/SQL procedure successfully completed.
SQL>
Ok, so that code works, but it's a bit messy with all those nested IF statements. Is there a cleaner way perhaps? Wouldn't it be nice if we could set up our own exceptions...
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure re_order(p_item_id NUMBER, p_quantity NUMBER) is
2 cursor cur_stock_reorder is
3 select s.stock_level
4 ,r.stock_level as reorder_level
5 ,(r.stock_level*4) as reorder_limit
6 from stock s join reorder_level r on (s.item_id = r.item_id)
7 where s.item_id = p_item_id;
8 --
9 v_stock cur_stock_reorder%ROWTYPE;
10 --
11 -- Let's declare our own exceptions for business logic...
12 exc_not_warranted EXCEPTION;
13 exc_too_much EXCEPTION;
14 begin
15 OPEN cur_stock_reorder;
16 FETCH cur_stock_reorder INTO v_stock;
17 IF cur_stock_reorder%NOTFOUND THEN
18 RAISE no_data_found;
19 END IF;
20 CLOSE cur_stock_reorder;
21 --
22 IF v_stock.stock_level >= v_stock.reorder_level THEN
23 -- Stock is not low enough to warrant an order
24 RAISE exc_not_warranted;
25 END IF;
26 --
27 IF v_stock.stock_level + p_quantity > v_stock.reorder_limit THEN
28 -- Required amount is over-ordering
29 RAISE exc_too_much;
30 END IF;
31 --
32 DBMS_OUTPUT.PUT_LINE('Order OK. Printing Order...');
33 -- Here goes our code to print the order
34 --
35 exception
36 WHEN no_data_found THEN
37 CLOSE cur_stock_reorder;
38 DBMS_OUTPUT.PUT_LINE('Invalid Item ID.');
39 WHEN exc_not_warranted THEN
40 DBMS_OUTPUT.PUT_LINE('Stock has not reached re-order level yet!');
41 WHEN exc_too_much THEN
42 DBMS_OUTPUT.PUT_LINE('Quantity specified is too much. Max for this item: '
||to_char(v_stock.reorder_limit-v_stock.stock_level));
43* end;
SQL> /
Procedure created.
SQL> exec re_order(10,100);
Invalid Item ID.
PL/SQL procedure successfully completed.
SQL> exec re_order(3,40);
Stock has not reached re-order level yet!
PL/SQL procedure successfully completed.
SQL> exec re_order(1,100);
Quantity specified is too much. Max for this item: 70
PL/SQL procedure successfully completed.
SQL> exec re_order(2,50);
Order OK. Printing Order...
PL/SQL procedure successfully completed.
SQL>
That's better. And now we don't have to use all those nested IF statements and worry about it accidently getting to code that will print the order out as, once one of our user defined exceptions is raised, execution goes from the Statements section into the Exception section and all handling of errors is done in one place.
Now for the second sort of user defined exception...
A new requirement has come in from the Finance department who want to have details shown on the order that show a re-order 'indicator' based on the formula ((maximum allowed stock - current stock)/re-order quantity), so this needs calculating and passing to the report...
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure re_order(p_item_id NUMBER, p_quantity NUMBER) is
2 cursor cur_stock_reorder is
3 select s.stock_level
4 ,r.stock_level as reorder_level
5 ,(r.stock_level*4) as reorder_limit
6 ,(((r.stock_level*4)-s.stock_level)/p_quantity) as finance_factor
7 from stock s join reorder_level r on (s.item_id = r.item_id)
8 where s.item_id = p_item_id;
9 --
10 v_stock cur_stock_reorder%ROWTYPE;
11 --
12 -- Let's declare our own exceptions for business logic...
13 exc_not_warranted EXCEPTION;
14 exc_too_much EXCEPTION;
15 begin
16 OPEN cur_stock_reorder;
17 FETCH cur_stock_reorder INTO v_stock;
18 IF cur_stock_reorder%NOTFOUND THEN
19 RAISE no_data_found;
20 END IF;
21 CLOSE cur_stock_reorder;
22 --
23 IF v_stock.stock_level >= v_stock.reorder_level THEN
24 -- Stock is not low enough to warrant an order
25 RAISE exc_not_warranted;
26 END IF;
27 --
28 IF v_stock.stock_level + p_quantity > v_stock.reorder_limit THEN
29 -- Required amount is over-ordering
30 RAISE exc_too_much;
31 END IF;
32 --
33 DBMS_OUTPUT.PUT_LINE('Order OK. Printing Order...');
34 -- Here goes our code to print the order, passing the finance_factor
35 --
36 exception
37 WHEN no_data_found THEN
38 CLOSE cur_stock_reorder;
39 DBMS_OUTPUT.PUT_LINE('Invalid Item ID.');
40 WHEN exc_not_warranted THEN
41 DBMS_OUTPUT.PUT_LINE('Stock has not reached re-order level yet!');
42 WHEN exc_too_much THEN
43 DBMS_OUTPUT.PUT_LINE('Quantity specified is too much. Max for this item: '
||to_char(v_stock.reorder_limit-v_stock.stock_level));
44* end;
SQL> /
Procedure created.
SQL> exec re_order(2,40);
Order OK. Printing Order...
PL/SQL procedure successfully completed.
SQL> exec re_order(2,0);
BEGIN re_order(2,0); END;
ERROR at line 1:
ORA-01476: divisor is equal to zero
ORA-06512: at "SCOTT.RE_ORDER", line 17
ORA-06512: at line 1
SQL>
Hmm, there's a problem if the person specifies a re-order quantity of zero. It raises an unhandled exception.
Well, we could put a condition/check into our code to make sure the parameter is not zero, but again we would be wrapping our code in an IF statement and not dealing with the exception in the exception handler.
We could do as we did before and just include a simple IF statement to check the value and raise our own user defined exception but, in this instance the error is standard Oracle error (ORA-01476) so we should be able to capture it inside the exception handler anyway... however...
EXCEPTION
WHEN ORA-01476 THEN
... is not valid. What we need is to give this Oracle error a name.
This is done by declaring a user defined exception as we did before and then associating that name with the error number using the PRAGMA EXCEPTION_INIT statement in the declaration section.
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure re_order(p_item_id NUMBER, p_quantity NUMBER) is
2 cursor cur_stock_reorder is
3 select s.stock_level
4 ,r.stock_level as reorder_level
5 ,(r.stock_level*4) as reorder_limit
6 ,(((r.stock_level*4)-s.stock_level)/p_quantity) as finance_factor
7 from stock s join reorder_level r on (s.item_id = r.item_id)
8 where s.item_id = p_item_id;
9 --
10 v_stock cur_stock_reorder%ROWTYPE;
11 --
12 -- Let's declare our own exceptions for business logic...
13 exc_not_warranted EXCEPTION;
14 exc_too_much EXCEPTION;
15 --
16 exc_zero_quantity EXCEPTION;
17 PRAGMA EXCEPTION_INIT(exc_zero_quantity, -1476);
18 begin
19 OPEN cur_stock_reorder;
20 FETCH cur_stock_reorder INTO v_stock;
21 IF cur_stock_reorder%NOTFOUND THEN
22 RAISE no_data_found;
23 END IF;
24 CLOSE cur_stock_reorder;
25 --
26 IF v_stock.stock_level >= v_stock.reorder_level THEN
27 -- Stock is not low enough to warrant an order
28 RAISE exc_not_warranted;
29 END IF;
30 --
31 IF v_stock.stock_level + p_quantity > v_stock.reorder_limit THEN
32 -- Required amount is over-ordering
33 RAISE exc_too_much;
34 END IF;
35 --
36 DBMS_OUTPUT.PUT_LINE('Order OK. Printing Order...');
37 -- Here goes our code to print the order, passing the finance_factor
38 --
39 exception
40 WHEN exc_zero_quantity THEN
41 DBMS_OUTPUT.PUT_LINE('Quantity of 0 (zero) is invalid.');
42 WHEN no_data_found THEN
43 CLOSE cur_stock_reorder;
44 DBMS_OUTPUT.PUT_LINE('Invalid Item ID.');
45 WHEN exc_not_warranted THEN
46 DBMS_OUTPUT.PUT_LINE('Stock has not reached re-order level yet!');
47 WHEN exc_too_much THEN
48 DBMS_OUTPUT.PUT_LINE('Quantity specified is too much. Max for this item: '
||to_char(v_stock.reorder_limit-v_stock.stock_level));
49* end;
SQL> /
Procedure created.
SQL> exec re_order(2,0);
Quantity of 0 (zero) is invalid.
PL/SQL procedure successfully completed.
SQL>
Lastly, let's look at raising our own exceptions with our own exception numbers...
SQL> ed
Wrote file afiedt.buf
1 create or replace procedure re_order(p_item_id NUMBER, p_quantity NUMBER) is
2 cursor cur_stock_reorder is
3 select s.stock_level
4 ,r.stock_level as reorder_level
5 ,(r.stock_level*4) as reorder_limit
6 ,(((r.stock_level*4)-s.stock_level)/p_quantity) as finance_factor
7 from stock s join reorder_level r on (s.item_id = r.item_id)
8 where s.item_id = p_item_id;
9 --
10 v_stock cur_stock_reorder%ROWTYPE;
11 --
12 exc_zero_quantity EXCEPTION;
13 PRAGMA EXCEPTION_INIT(exc_zero_quantity, -1476);
14 begin
15 OPEN cur_stock_reorder;
16 FETCH cur_stock_reorder INTO v_stock;
17 IF cur_stock_reorder%NOTFOUND THEN
18 RAISE no_data_found;
19 END IF;
20 CLOSE cur_stock_reorder;
21 --
22 IF v_stock.stock_level >= v_stock.reorder_level THEN
23 -- Stock is not low enough to warrant an order
24 [b]RAISE_APPLICATION_ERROR(-20000, 'Stock has not reached re-order level yet!');[/b]
25 END IF;
26 --
27 IF v_stock.stock_level + p_quantity > v_stock.reorder_limit THEN
28 -- Required amount is over-ordering
29its nice article, have put up this one the blog
site,Nah, I don't have time to blog, but if one of the other Ace's/Experts wants to copy it to a blog with reference back to here (and all due credit given ;)) then that's fine by me.
I'd go for a book like "Selected articles by OTN members" or something. Does anybody have a list of links of all those mentioned articles?Just these ones I've bookmarked...
Introduction to regular expressions ... by CD
When your query takes too long ... by Rob van Wijk
How to pipeline a function with a dynamic number of columns? by ascheffer
PL/SQL 101 : Exception Handling by BluShadow -
Failover exception handling in partnerlink
Hi All,
I've been trying to test the failover exception handling feature in partnerlink and were not able to replicate it. Can you please assist me on this? Here is the steps which I've carried out:
1.) Develop a web service and deploy to my localhost's OC4J instance with the following ending point:
http://localhost:8888/plsqlwebService-webservice-context-root/plsqlwebserviceSoapHttpPort
2.) Develop the same web service and deploy it to my testing application server with the following ending point:
http://myappserver:8888/plsqlwebService-webservice-context-root/plsqlwebserviceSoapHttpPort
3.) Create a bpel synchronous project with a partnerlink originally pointing to my testing application server WSDL file. Also, I've created a Location property for that same partnerlink with 2 sets of values - first having the ending point of my testing application server and the second one is the ending point of my local OC4J instance.
4.) Deploy the deploy Bpel project to my testing application server.
5.) To test it, I purposely disabled the web service created in step 2 and initiate the Bpel project on the Bpel console. I was hoping that because the primary web service is not available and it will try to call the second one which I've defined in the Location property but it did not work.
Have I misunderstood the concept or missed out some important tasks? Thank you for your timne and assistance.
Have a nice day,
JohnHi Jayakrishna,
In General , there are non execptions in BAPIs, because of the reason, that the exception raised in a SAP envoronment may not mean anything for a non SAP initiator. All the exception situations would only fill the return table(TYpe BAPIRET2 or something like that). If you read that table after the call to the bapi, you can understand what has gone wrong.
Regards,
Ravi -
Generic error/exception handler
Well guys, I think I got a challenge for you: I have been thinking for some time about the idea of having a generic error handler for my applications. It's one of these things you should just have: In large GUI apps you usually try to catch all exceptions and display some sort of nice error dialog telling the user what went wrong and what he has to do now. However, there are runtime errors that one can't foresee. These might be bugs, sure, but they happen, so there should be a way of dealing with them. For example, let's say there is a NullPointerException. The clean way would be to display a message box saying something like "Bug!" and giving the user the chance to save his work (or do that automatically). However, this does not seem to be possible. Sure, I could surround every method code with a try { ... }catch(Exception e) and display the dialog, but that seems rather tedious. Does anyone know a better way? Like a common error handling method that is always called when there is an uncaught exception. I dunno, but my IDE JBuilder has something like that, because it is able to stop at "all uncaught exceptions". Any suggestions?
Thanks guys, or do we have to file a RFE???
Filip RindlerWell, that doesn't work for GUI apps as their main method is done after initializing and all other work is done by the event dispatch thread that is responsible for receiving OS messages (such as mouse motion / clicked / ...). Then this thread calls the event listener methods of registered listeners. It's actually a little more complex how AWT/Swing handles things, but that's the general concept and it is the core of the problem as well: I cannot change any of the event dispatch code (it's deep down in the AWT), so therefore I cannot catch any exceptions there. But maybe there's a hook...
-
MC.9 and MCY1 and Exception Handling in (Logistics Inf. Sys)LIS
Hi,
I want the 'Valuated Stock Value" greater then or equal to zero (>=) appear in the MC.9 report. I can create 'Exception' in MCY1 but am unable to do so. Once I am in MCY1; I choose 'Requirements' then Key Figure 'Valuated Stock Value' then 'Type of condition' is 'Threshold Val. Anal.' is set to '> 0'. However, the report still displays zero values in MC.9. I don't want to display 'Valuated Stock Value' zero to be displayed on the report. Please help.
Thanks
NavedHey Chris,
I got the point for exception handling in weblogic 9.2. We ae using 9.2. It comes up with the concept of shared page flows which means all my unhandled exceptions are thrown to the shared page flow controller. There based on the type of exception, i can forward the request to appropraite page.
Thanks anywyas,
Saurabh -
Exception handling in rfcs and bapis
exception handling in rfcs and bapis
Hi Jayakrishna,
In General , there are non execptions in BAPIs, because of the reason, that the exception raised in a SAP envoronment may not mean anything for a non SAP initiator. All the exception situations would only fill the return table(TYpe BAPIRET2 or something like that). If you read that table after the call to the bapi, you can understand what has gone wrong.
Regards,
Ravi -
Exception Handling In BPEL By using Catch Blocks or Fault Policies Or Both
I have a confusion regarding
Exception handling :
When Should i go for 1)Catch Block (Remote , or binding ) in bpel for exception handling .
2)Fault Policy , Fault binding.xml
Currently iam using catch blocks , but even fault policy is good , but can i use both...
Currently in My bpel ,when any error occurs i have to send a error notification by Email .
Currently i have exposed the email service which shuts emails and write a file with errored Message.
Hence if any error i will catch i in a parent BPEL, i will just invoke the above email, service .
So anybody can help me by giving the suggestion how to go for the best approach
Edited by: anantwag on Mar 23, 2011 6:31 AMCurrently in My bpel ,when any error occurs i have to send a error notification by Email .
Currently i have exposed the email service which shuts emails and write a file with errored Message.Seeing your use case I will suggest you to use fault handling framework (fault policy). Fault handling framework should be used where you need generic error handling framework which handles all the faults occured in any composite component. Generally BPEL catch block should be used to propagate error info/fault back to the client/to fault handling framework or to consume an error
Regards,
Anuj -
In the current project my exception handling implementation is as follows :
Exception Handling Layer wise :
DL layer :
catch (Exception ex)
bool rethrow = ExceptionPolicy.HandleException(ex, "Ui Policy");
if (rethrow)
throw;
BL Layer
catch (Exception ex)
bool rethrow = ExceptionPolicy.HandleException(ex, "Ui Policy");
if (rethrow)
throw;
UI Layer
catch (Exception ex)
bool rethrow = ExceptionPolicy.HandleException(ex, "Ui Policy");
if (rethrow)
Response.Redirect("ErrorPage.aspx", false);
We have a tool to check the standards. And tool output is as follows :
The exception Exception should never been thrown. Always Subclass Exception and throw the subclassed Classes.
I need suggestions on how to implement the same according to standards.Your tool is wrong if it says to never throw Exception. This was a common recommendation back in the .NET v1 days but has long since been thrown out. It is perfectly fine to use Exception when you have a general exception that provides no information
that an application can use to make an informed opinion.
The general rules of exception throwing is to throw the most specific exception that makes sense. If there is no specific exception that applies and it would be useful for the caller to handle the exception differently than other exceptions then creating
a custom exception type is warranted. Otherwise throwing Exception is reasonable. As an example you might have an application that pulls back product data given an ID. There is no built in exception that says the ID is invalid. However an invalid ID
is something that an application may want to handle differently than, say, an exception about the product being discontinued. Therefore it might make sense to create an ItemNotFoundException exception that the application can react to.
Conversely there is no benefit in having different exception types for disk full and disk quota met. The application will respond the same in either case.
Michael Taylor
http://blogs.msmvps.com/p3net -
Integration Process exception handling & alerts, Java
Hello,
I would like to enhance my basic scenarios fool proof and with as much Java as possible.
I have set up several asynchronous and synchronous File to SOAP transfers between systems A and B
using PI70 including my own Java mapping classes and PI's AF_Modules beans. They work just fine.
I have not designed my own Integration Processes yet, so execution is based on channel settings and availability timing.
I have learned this aproach may be exposed to general faults resulting manual monitoring and repairing.
For example server problems at receiver side can result data losses as sender channel just keeps removing source
files like normally, as the process would be better to just stop right there and alert or something.
My question is, is the "Enterprise services Builders" Integration Process & Graphical definition screen the one and only tool to
customize whole process exception handling and alerts in PI, and Java is not an option?
Appreciate your advice on this.
Kind regards mHi m,
Strange Name
>>I have learned this aproach may be exposed to general faults resulting manual monitoring and repairing. For example server problems at receiver side can result data losses as sender channel just keeps removing source files like normally, as the process would be better to just stop right there and alert or something.
If you are looking to handle this particular scenario, then we have the alert mechanism and CCMS monitoring. There you will come to know whether the end system down or not.
Also in addition to this you can write your own java (in message mapping, as modules, java mapping) /abap code (as abap mapping, user exit in standard functions etc) for providing more details in error scenarios. But you need to validate whether the maintenance/development cost for the code is justified in your scenarios
Regards
Suraj -
hi,
I have created a custom component that has a service which invokes my custom java methods. I would like to redirect to two error pages depending on the exception thrown by the java method? How exception handling is done in UCM. I see a text box called error messages while creating the service and service actions. But that message is not printed when my java method throws application specific exceptions.
Is there a way to handle the exception at Service configuraration / UI side and redirect to two different meaningful error pages dependinf upon the thye of exception
Thanks,
SivaHi Jayakrishna,
In General , there are non execptions in BAPIs, because of the reason, that the exception raised in a SAP envoronment may not mean anything for a non SAP initiator. All the exception situations would only fill the return table(TYpe BAPIRET2 or something like that). If you read that table after the call to the bapi, you can understand what has gone wrong.
Regards,
Ravi -
Exception Handling in Message Mapping and Alert
Hello,
1. Pls let me know the concept of Exception Handling and Alerts.
2. Pls provide some blogs for Exception Handling in Message Mapping.
3.What are Alerts and how it help us in XI. Pls provide some blogs for Alert
4.How are Alerts and Exception Handling can be related say for some scenario
RegardsHi,
Plz check out these blogs of Sravya on Error Handling:
/people/sravya.talanki2/blog/2006/11/22/error-handling-framework-xiout-of-the-box-episode-1
/people/sravya.talanki2/blog/2006/11/23/error-handling-framework-xiout-of-the-box-episode-2
Also check this SAP Presentation:
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/9418d690-0201-0010-85bb-e9b2c1af895b
/people/alessandro.guarneri/blog/2006/01/26/throwing-smart-exceptions-in-xi-graphical-mapping
Error Handling :
http://help.sap.com/saphelp_nw04/helpdata/en/56/b46c3c8bb3d73ee10000000a114084/frameset.htm
Alerts:
/people/michal.krawczyk2/blog/2005/09/09/xi-alerts--troubleshooting-guide
/people/michal.krawczyk2/blog/2005/09/09/xi-alerts--step-by-step
http://help.sap.com/saphelp_nw04/helpdata/en/56/d5b54020c6792ae10000000a155106/content.htm
BPM:
/people/arpit.seth/blog/2005/06/27/rfc-scenario-using-bpm--starter-kit
Working with acknowledgements
regards -
Exception handling in IDOC using workflows
exeception handling in idoc using workflows
i. what will be the trigerring event in case of idoc ?
ii.will it be BOR -- IDOC<message_type >?
thanks in advance
naval bhattHi Naval Bhatt,
it depends on what you would like to do, but there is an object IDOCAPPL, more information you find Objekttyp IDOC<MSGTYP>:
http://help.sap.com/saphelp_47x200/helpdata/en/04/92725546f311d189470000e829fbbd/frameset.htm
General how it works:
Objects, Events and Tasks to be Created
http://help.sap.com/saphelp_47x200/helpdata/en/78/2176d251ce11d189570000e829fbbd/frameset.htm
This is an example how the application should implement the exception handling in IDOC by using workflows.
Events for example:
- inputErrorOccurred
- inputFinished
Regards
Tibor -
Exception Handling in the OBI EE 10.1.3.4
Hi All,
Is it possible to implement the exception handling in the OBI EE 10.1.3.4
For Ex: Instead of displaying the below error, is it possible to display it in the meaningful way
[nQSError: 10058] A general error has occurred. [nQSError: 27002] Near : Syntax error [nQSError: 26012] . (HY000)
SQL Issued: SELECT SALES_FACT.SALES_AMOUNT, TIMESTAMPDIFF(SQL_TSI_DAY, TIMESTAMP ‘1900-01-01 12:00:00’, TIMESTAMP ‘1900-01-01 12:00:00’), TIME_DIM.BUSINESS_DATE FROM SALES
Thanks in Advance
SivaHi Deepak,
Thank you for responding to the query that i have raised.
As you mentioned that ORA: errors will help in diagnosing the issue.
Do you mean that it will help in diagnosing the issue at the BMM larey & Physical layer join conditions.
Thanks in Advance
Siva
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