Understanding on Exception handling???

Hi all
I am doing some bug correction on exception and encounter some problem and questions. Hope someone can help clear my doubts pls. Thanks.
Q1. I have an exception handling in method A whereby it throw an exception of type ERROR class. I try to catch this ERROR in method B with MyException class which extends from EXCEPTION class. I realise this cannot be done. When I change MyException class to Throwable class, I can catch ERROR thrown. Is it correct that I can only catch exception using superclass? Coz in this case MyException is not a superclass of ERROR class?
public class MyClass() throws MyException
void method B()
try{
method A();
}catch(MyException e){
system.println.out();
void method A()
try{
}catch(IndexOutOfBoundsException e){
throw new Error("string text');
Q2. Is it true that I cannot put methodA in MyClass because it throws ERROR class but MyClass throws only MyException?

Uh.. I think what you just said is called a
bug, which need to be caught.No ... bugs can cause exceptions, but there are several occasions when a exception can occur that have nothing to do with bugs.
If for example the hard disk is full when you want to save your file that can hardly be called a bug, but rather an unlucky occurance: an exception to the rule that normally there is enough space left on the drive.
Also: if somewhere a router shuts down, because it was hit by a lightning an consequently your connection is interrupted then that's not a bug (at least not in your program), but an exception that you must handle.
But as I said: bugs can cause exceptions: If you allocate a buffer of 1024 bytes and try to write to its 1025th byte then an ArrayIndexOutOfBoundsException is thrown. In this case you generally don't want to catch the exception, but rather prevent it from beeing thrown.

Similar Messages

Understanding Exception handler activity

All,
I created 2 view activities in my adfc-config.xml and established a navigation flow between them. The flow happens on click of a button on view1. I have defined an exception handler activity to show unhanded error that may arise. On click of the button in the view1, AM IMPL methods gets called and this is the code
    public void newPage(){
        int k = 5/0; //expecting the error handler activity to get invoked here
    } When i click on the button, i get the exception however the page associated with exception handler is not getting invoked. I want the exception handler page to be shown for error and not the default popups. How do we do that?
thnks
Jdev 11.1.1.5

No, this is only one possibility...
checkout Andrejus blog about exception handling http://andrejusb-samples.blogspot.com/2011/03/jdevadf-sample-exception-handler-for_19.html and of cause the docs http://download.oracle.com/docs/cd/E24382_01/web.1112/e16182/taskflows_complex.htm#BACJCBIC
Timo

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
29

its 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

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 ucm

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,
Siva

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 ODI - common exception handling framework

Hi,
I need to come up with a common exception handling framework in an environment where ESB and ODI are being used for interfacing and ELT operations. I am of the opinion that
1. I am not able to find any documentation wrt exception handling when ODI is used? Can some one help me with some pointers?
2, When I come up with a common exception handling framework using BPEL, will I be able to invoke the same from ODI.
Thanks,
Mahesh

Thanks for the reply Allan. I haven't used BusinessWorks.
I did go through this thread before and here's my understanding.
1. ESB provides the ability of error handling (client management API) but not the exception handling i.e. I can't redirect the flow in case there is an exception in my primary flow. Am I right with my understanding?
2. Error handling ability of ESB is limited to retryable exceptions viz-a-viz asynchrounous ESB processes (e.g. database listener not up) where in the process can be retried. Am I right here?
Thanks,
Mahesh

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,
John

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

Removing Exception Handling Causes Compiler Error

I am very new to Java. I have a background in other programming languages including Ruby. I am in need of a convenient means to parse XML code. I picked up the code shown at the end of this message on the Internet. In its original form, it works perfectly. I experimented by trying to comment out the try block as you can see. I was surprised to find that in that form it wouldn't compile. In essence, I thought what I was doing was simply removing exception handling. I figured that since the code worked and there were no exceptions being thrown, it would work just fine for experimentation purposes. (I understand that I would not want to do this in production mode.) Can someone please explain to me why removing the exception handling causes the program to fail to compile?
Thanks for any input.
... doug
/* Experimental Code */
/* http://www.mkyong.com/java/how-to-read-xml-file-in-java-dom-parser/ */
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.io.File;
public class ReadXMLFile {
public static void main(String argv[]) {
try {
File fXmlFile = new File("ReadXMLFile.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);
doc.getDocumentElement().normalize();
System.out.println("Root element :" + doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("staff");
System.out.println("-----------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("First Name : " + getTagValue("firstname",eElement));
System.out.println("Last Name : " + getTagValue("lastname",eElement));
System.out.println("Nick Name : " + getTagValue("nickname",eElement));
System.out.println("Salary : " + getTagValue("salary",eElement));
} catch (Exception e) {
e.printStackTrace();
private static String getTagValue(String sTag, Element eElement){
NodeList nlList= eElement.getElementsByTagName(sTag).item(0).getChildNodes();
Node nValue = (Node) nlList.item(0);
return nValue.getNodeValue();
}

877757 wrote:
I figured that since the code worked and there were no exceptions being thrown, it would work just fine for experimentation purposes. The compiler doesn't know that your code works. It only knows that some method you call can throw some checked exception, and it requires you to catch it or declare that you don't.

Exception handling with fault message type not working

Hi,
I have a sync proxy to proxy scenario and I have created a fault MT and specified in the outbound and Inbound service interface...
*In Inbound proxy I have the following code--*......
RAISE EXCEPTION TYPE z_cx_test_fault
EXPORTING
standard = l_standard_data.
In the sender side abap code which calls the outbound proxy I have the follwing code -
CATCH cx_ai_system_fault INTO lo_cx_ai_system_fault.
txt = lo_cx_ai_system_fault->get_text( ).
WRITE txt.
CATCH z_cx_test_fault INTO lo_cx_test_fault.
txt = lo_cx_standard_message_fault->get_text( ).
WRITE txt.
CATCH cx_ai_application_fault INTO lo_cx_ai_application_fault.
txt = lo_cx_ai_application_fault->get_text( ).
WRITE txt.
when i test the inbound proxy separately I get the custom fault message properly...
however when i run the proxy to proxy sync scenario and the custom exceptionz_cx_test_fault is raised inside the receiver proxy .......control goes to CATCH cx_ai_application_fault and not CATCH z_cx_test_fault .
I understand that cx_ai_application_fault is the super class of all the exception class but why does control go to its exception handling when a custom exception is raised...
Edited by: hema T on Feb 26, 2012 1:16 PM
Edited by: hema T on Feb 26, 2012 1:17 PM

Hi
I tried changing the sequence also but it did not work...
I can see an appropriate response coming from the receiver in SXMB_MONI of PI...this response has the "fault response "
"fault detail" data that I want.....however when the control goes to the sender why does it go to CATCH CX_AI_APPLICATION_FAULT and not not my CATCH z_cx_test_fault .
My observation - If I change the scenario to SOAP to Proxy sync..then the sender SOAP client gets the appropriate custom fault message back.
Edited by: hema T on Feb 27, 2012 1:17 PM
Edited by: hema T on Feb 27, 2012 1:17 PM

Reboot due to system error / Register dump from exception handler

hi,
I have a problem with Labview RT when using Reboot function.
The RT target (desktop) reboot but there is a message : Reboot due to system error. And if I reboot once again, the target become in safe mode.
Now, If I look at the log I obtain the following message see more in the log attached!
*** REGISTER DUMP FROM EXCEPTION HANDLER (code 0x80000003) ***
I don't understand why there is this message.
Anybody has an explaination?
Attachments:
Nouveau Document texte2.txt ‏6 KB

julesjay a écrit:
ok I didn't know that. I will wait for tomorrow.
NI france is not very efficient about labview Real time problems.
There is one or two experts and there aren't easily reachable.
So a lot of question I send stay with no answer.....
That why I hope someone will be able to help me.
Hi Julesjay,
After i have see your log file and the problem, i think NI FRANCE are working on your request for all problems you have in your application.
And i don't understand what you say that, because we have make test, we have send us informations for make different tests, and we are still working on your problem.
I know the problem are not resolved, but we are working for resolve it quickly.
I suggested you to contact the AE that are your service request for have more information.
Best regards,
Christophe S.
FSE East of France І Certified LabVIEW Associate Developer І National Instruments France

Fundamental exception handling irritation

Hello experts,
I have come across a very disturbing effect when using a function module capable of asynchronous execution in a try-cleanup-endtry statement. Please have a look at the following simple construct:
TRY.
 do_some_db_update( ).
 start_proc_chain_with_fm( ).
 COMMIT WORK.
CLEANUP.
 ROLLBACK WORK.
ENDTRY.
The method do_some_db_update( ) can raise an exception (when the update statement contained in it somehow fails). The method start_proc_chain_with_fm( ) uses the fm RSPC_API_CHAIN_START to start some process chain, if it returns with return code failed we raise an exception too.
That is, both methods potentially raise exceptions. Obviously we only want to commit the involved DB changes if neither does and we want to roll back things if one of the two raises an exception (before propagating the exception to a caller).
Now, what happens occasionally is that the latter method fails, i.e. it actually raises an exception, however the programm flow executes both, the remaining code in the try-block (i.e. the COMMIT statement) as well as the CLEANUP-branch (i.e. the ROLLBACK statement, which of course has nothing to roll back by then anymore).
Can somebody please shed some light on this, I am very confused. This behavior upsets the very basis of my understanding of how exception handling in try-catch blocks works.
Of course I somehow suspect the function module's "asychronous" capabilities.. but actually I think this must not have an effect on the construction as such.
Regards,
Sebastian

Hi Matt,
thanks for you answer. The exception thrown is indeed my chain_start_failed_ex (my class-based wrapper around/equivalent of the original failed-"exception" returned by the function module). That is, an exception is thrown and the programm flow should definitly continue after the CLEANUP statement. However, this is not always the case.
As for your proposal this could be a work-around for the concret problem. Nevertheless I would very much like to find a general explanation for this "mystery". In principle I think - regardless of what the methods actually do - the effect discribed should never happen..
Regards,
Sebastian

Common Exception Handling

I am trying to create a single BPEL process which is called from all my processes to handle a fault condition. To do this I need to pass in the complete error from the console.
So for example I get the following error if I add no exception handling to my web service call (i.e. the process goes RED) :
<bindingFault>
<part name="code" >
<code>GenericError</code>
</part>
<part name="summary" >
<summary>Failed get wsdl service definition. Failed to get a WSDL service that support the portType "{http://ManualErrorHandler.integration}ManualExceptionHandler" in WSDL definition "{http://ManualErrorHandler.integration}
ManualExceptionHandler". Please verify that WSDL portType "{http://ManualErrorHandler.integration}
ManualExceptionHandler" is supported by a service in WSDL file. </summary>
</part>
</bindingFault>
I would like to pass this complete text as a string input into my common process.
Can this be done? I do not seem to be able to copying this data in an Assign...
Pete

Thanks for the reply Allan. I haven't used BusinessWorks.
I did go through this thread before and here's my understanding.
1. ESB provides the ability of error handling (client management API) but not the exception handling i.e. I can't redirect the flow in case there is an exception in my primary flow. Am I right with my understanding?
2. Error handling ability of ESB is limited to retryable exceptions viz-a-viz asynchrounous ESB processes (e.g. database listener not up) where in the process can be retried. Am I right here?
Thanks,
Mahesh

RE: exception handling

Wayne,
When an exception occurs, Forte aborts the inner
most compound statement, after executing the code
of an exception handler if there is one. If the excep-
tion is not handled, it still exists after the compound
statement was aborted, so Forte now aborts the
remaining inner most compound statement. This
continues until Forte reaches the root compound
statement of the tread (or "task" if you will). This
one will also be aborted and that is the end of the
thread (task). If you look at the debugger, you will
see "RIP" in front of this thread. Sure, this thread
was spawned by another thread. It was started
by a "start task" call from within some compound
statement in the parent thread, but this compound
statement was probably long since closed. Forte
can't pass the exception on to a higher level com-
pound statement, because there is none. If the
thread started with a method that had a return event
and an exception event, and you started the task
with "Completion = event" then Forte will post one
of these events after the root compound statement
was finished (in other words, the thread was stopped).
From this event you can see, if the thread wasfinished succesfully or not.
Of course, an event is not the same kind of thing
as an exception. You can't raise events, or post
exceptions.
So, when an exception is not handled, only the thread
where this exception occured is cancelled (including
all it's child threads). The rest of the treads stay alive.
-----Original Message-----
From: Wayne Walker [SMTP:[email protected]]
Sent: Wednesday 22 July 1998 13:49
To: '[email protected]'
Subject: exception handling
I have a problem in handling exceptions detected in a task. I start a
task
which performs some function. I also have an event handler which
recognizes the method_exception returned should an exception be
detected.
Once detected by the event handler I force the exception up to
another
process which displays the exception to the user. However, it appears
that
forte is intercepting the exception before my event handler can detect
it
and posts an exception message. Can anyone explain how this mechanism
works and the best approach for handling exceptions myself vice Forte?
Thanks,
Wayne
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My understanding is that if your client doesn't care (or cannot handle) the exception,
you throw your exception WRARPPED with EJBException. This way, the container can
roll back the transaction properly.
If your client cares (or have the ability to recover) the exception, you should
define your own exception. They should not be derived from RuntimeException or
RemoteException or EJBException. If you want to make sure that the transactions
are rolled back, you call setRollbackOnly() before you throw the exception.
Charles
soraya abbasi <[email protected]> wrote:
I have tried to make my custom exception subclass RemoteException but
that doesn't work.
Does that mean to say you can't have custom exceptions thrown to a client?

Exception handling - Common exception handling framework

Hi,
I need to come up with a common exception handling framework in an environment where ESB and ODI are being used for interfacing and ELT operations. I am of the opinion that
1. A generic exception handling framework can be built using BPEL and can be invoked from ESB. Is my understanding correct?
2. Are there any ways that we can build this framework using ESB itself? I opinion that it's not possible as there is no concept of try-catch?
3. I am not able to find any documentation wrt exception handling when ODI is used? Can some one help me with some pointers?
4, When I come up with a common exception handling framework, will I be able to invoke the same from ODI.
Thanks,
Mahesh

Thanks for the reply Allan. I haven't used BusinessWorks.
I did go through this thread before and here's my understanding.
1. ESB provides the ability of error handling (client management API) but not the exception handling i.e. I can't redirect the flow in case there is an exception in my primary flow. Am I right with my understanding?
2. Error handling ability of ESB is limited to retryable exceptions viz-a-viz asynchrounous ESB processes (e.g. database listener not up) where in the process can be retried. Am I right here?
Thanks,
Mahesh

Exception Handling in Object Oriented Design

I am developing a huge web based project using Object Oriented design and java,srvlets ,jsp etc ,I am using 3-tier archtecture.I dont understand,how i should handle exceptions in my project.ie.If there is some exception in the base modules how should it be handled.What kind of excpetion Structure should i use,How many exception classes should be made etc,
Can someone help me in this regard

A couple things I have found to be good practices for exception handling in an n-tier architecture:
1. Don't expose all the internal exceptions of a tier to the client of the tier. Create a more useful, descriptive set of exceptions (or use the appropriate predefined exceptions) to throw up to the client.
For example, on one project, we are doing database access among other things in the "service" tier, which is accessed by the web tier. We catch the SQLExceptions, PersistenceExceptions (a custom exception), and others, and throw a more useful exception that the client will know how to handle such as a NoMeasurementResultsException if the client asks for measurement results when we have none.
2. Chain your exceptions and/or log the root cause in the tier that re-throws a different exception. There is nothing more aggravating than not knowing why, when you are debugging a problem, you are getting a NoMeasurementResultsException when you know that there ARE results in the database.
Hope these ideas help in your design.
Cheers,
Colin

Understanding on Exception handling???

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