Exception Handling at class level
This is a quick one. I've never used a try catch event handling statement at the class level where I declare all my variables before. Is is ok to do this? Can someone perhaps show me some psuedo code like this?
private final ImageIcon[] CAT_BULLETS = {new ImageIcon("yellow_his.gif"),
new ImageIcon("blue_pp.gif"), new ImageIcon("pink_sn.gif"),
new ImageIcon("brown_ent.gif"), new ImageIcon("green_al.gif"),
new ImageIcon("orange_sl.gif")};
No, you can't wrap class-level variable declarations in try-catch blocks. Declare
the variables at the class level, do the assignment in you constructor,
and wrap the code there in a try-catch block.
Similar Messages
-
Class based exception handling
Hi everyone....
I am new to object oriented abap.
I would like to know more about exception handling using classes.
please provide some good material or links on the topic?
Points will be rewarded.......hi,
Download the PDF from here.
http://www.esnips.com/doc/6d16a298-9227-4d32-acf1-e91164c89daf/3-ABAP-Objects(P283)
Follow this link too for tutorials.
http://www.****************/Tutorials/OOPS/MainPage.htm
Hope this helps, Do reward.
Edited by: Runal Singh on Mar 14, 2008 3:28 PM -
Exception Handling for many bean objects of a container class in a JSP page
Hello,
I have on container bean class. In this container class, there are several others class objects and the getter methods to get these objects out to the JSP pages.
I have one JSP page which will use different objects in the container class object through the getter methods of the container class.
My question is how to implement the exception handler for all the objects in the container so that the JSP page can handle all exceptions if occurrs in any object in the container?
Please give me some suggestions. Thanks
TuThanks for your reply.
Since the container is the accessor class, I have no other super class for this container class, I think I will try the try catch block in the getter methods. -
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 -
Exception handling across multiple classes
Is it possible to throw the exception from one class to another class for exception handling.............. can anyone tell me the way........
you don't throw it to a specific class. in the method where the exception might be thrown, you can choose to either catch it there, or just re-throw it so that the method before it can choose to catch it or throw it. you know what a stack trace is? it's a chain of methods that were called to get to a certain point in execution, and if an exception is thrown somewhere, either the method in which it is thrown deals with it, or it passes it back to the preceeding method in the stack
why were you trying to throw it to a class? -
Customised Exception handling class.....
Hello Friends,
I am working on a project for which I need to create my own exception handling class.
The reason I need this class is to catch any exceptions and get a customised error message
according to each exception and then be able to display those messages on web page.
some examples of the exception I want to catch and display appropriate message are..
1. a duplicate reord in db
2. wrong data type (this will deal with ints,doubles and strings data types)
3. date type validation ( to make sure its date object instead of a string)
and there are several more messages but if can get some help or idea from any one to design a class for the above errors I might be able to manage other errors as well.
greatly appreciate any respnses.First off, you can extend Exception:
public class MyException extends Exception {
}You can put some custom messages into the class:
public class MyException extends Exception {
public static final String DUPLICATE_RECORD = "Duplicate record in db",
WRONG_DATA_TYPE = "Wrong data type",
VALIDATION_ERROR = "Invalid data type";
}Then, have your constructors, which take a String as an argument, so they can get your 'presets' or a custom message:
public class MyException extends Exception {
public static final String DUPLICATE_RECORD = "Duplicate record in db",
WRONG_DATA_TYPE = "Wrong data type",
VALIDATION_ERROR = "Invalid data type";
public MyException(String message) {
super(message);
}You could also have a series of exception classes: DuplicateRecordException, WrongDataTypeException, ValidationException, etc. Hope that helps.
m -
Handling exceptions at Sub-Process Level
Can we handle exceptions at Sub-Process level itself? Or do we need to transfer the exceptions to the main process and then only the admin user can handle them?
The same thing applies to subprocesses. A subprocess is just a process that has been invoked by another process and the same exception handling rules apply to it.
You can catch exceptions in any process using:
<li> logic at the activity level using a try/catch block
<li> an activity using an Exception transition
<li> a Group in the process using an Exception transition
<li> the process using an Exception Handler
At a minimum, catch the "Others" exception using the Exception Handler. This ensures uncaught exceptions are not sent to the End activity (the default) and the instances are not lost. This simple best practice will save you days of debugging and several calls to customer support to resolve.
Dan -
Best Practice for Implementing Exception Handling in BPEL
Hi All,
what is the best practice and the approach to follow Exception Handling in BPEL.
1) Do we need to implement Exception Handling in BPEL as we do in Java, means
method 3 throws error to method 2 (if any) and
method 2 throws error to method 1 (if any) and
finally method 1 throws error to the main Class.
If we replicate the above scenario to BPEL
In BPEL main Scope have Custom Fault, Catch ALL
Each Invoke is surrounded by a Scope Activity with Remote Fault, Binding Fault & Custom Fault
and follow the paradigm of Java, assuming we have Inner Scopes
[ OR ]
2) In BPEL main Scope have all exceptions defined like
Remote Fault,
Binding Fault,
anyOther System Fault (selectionFailure / forcedTermination),
Custom Fault (if required) and
CatchALL
and also
each Invoke is surrounded by a Scopes Acitivity with Custom Fault (business fault) exception Handling
I feel 1st one may not be a good practice, may be i am wrong...
Any Suggestions from experts.
Thanks in Advance
anvv sharmaHi-
In you can create different scope and use catch branch to catch binding, remote, custom faults, business faults etc. If an error happens in a scope it will not move to the next scope( eg: you have 3 scope, error occured in 2nd scope then it will not propogate to the 3rd scope. One thing to be noticed here is your transaction in the 1st scope doesnt gets commited when an error happens in 2d scope).
You can have a catch all to catch error which are not being caught at catch level. So if any error happens which is not defined in catch block then then it will be caught in catch all branch.
Edited by: 333333 on Apr 12, 2011 9:39 AM -
Never implemented exception handling in Stored Procedures
I have lots of stand alone stored procedures callled from .NET 20 programs that follow the following pattern. They runn against Oracle 10.2 on Win2003. The only deviiation is a couple where I insert to temptables. I specify a parameter for messages but don't know the best way to implement for Oracle as well as any tips on ODP.NET/oracle interactions error handling.
1. Is it recommended to implement exception handling in With Clauses?
2. If there is an exception in one cursor's SQL, how do I still execute the second?
3. Is it best in some circumstances to pass a null back to client and check for null in program?
From .NET programs I have run into a couple of problems.
4. TNS packet failure.
Anyways any suggestions or experiences are welcome.
CREATE OR REPLACE PROCEDURE GET_SALES_DATA
, p_businessdate in date
, p_message out varchar2
, p_rcSales out sys_refcursor
, p_rInventory out sys_refcursor
) is
open p_rcSales for
with somedata as (select ...)
, someMoreData as (selct ...)
-- Main select
Select * from somedata sd inner join somemoredata smd on smd.key = sd.key;
open p_rcInventory for
with somedata as (select ...)
, someMoreData as (selct ...)
-- Main select
Select * from somedata sd inner join somemoredata smd on smd.key = sd.key;
-- CODE NOT IMPLEMENTED
-- exception
-- when TOO_MANY_ROWS then select 'Error handling for future implementations' into p_message from dual ;
-- when NO_DATA_FOUND then select 'Error handling for future implementations. No data' into p_message from dual;
-- when others then raise_application_error(-20011,'Unknown Exception in GET_SALES_DATA Function');
-- WHEN invalid_business_date then select 'Invalid: Business date is in the current work week.' into p_message from dual ;
END GET_SALES_DATA;Pseudocode'ish because Module level variables and properties have not been defined here for brevity.
Public Class WebPage1
PAge_Load
GetData
End Class Data Access Layer
Public Class DAL
Public Sub GetOracleData()
Dim conn As OracleConnection
Try
conn = New OracleConnection
Catch ex As Exception
Throw ex
End Try
Dim cmd As New OracleCommand
With cmd
conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("MyConnectionString").ToString
cmd.CommandText = DATABASE.GetSalesData
cmd.CommandType = CommandType.StoredProcedure
cmd.Connection = conn
End With
cmd.Connection = conn
Dim oparam As OracleParameter
oparam = cmd.Parameters.Add("p_businessdate", OracleDbType.Date)
oparam.Value = BusinessDate.ToString("dd-MMM-yy")
oparam = cmd.Parameters.Add("p_message", OracleDbType.Varchar2, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rc_inven_csv", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcSales", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcInventory", OracleDbType.RefCursor, ParameterDirection.Output)
Dim Adapter As New OracleDataAdapter(cmd)
Try
Adapter.TableMappings.Add("Table", Sales)
Adapter.TableMappings.Add("Table1", Inventory)
Adapter.Fill(dsOracleData)
Catch ex As OracleException
HandleError("Exception Retrieving Oracle Data", ex, MethodInfo.GetCurrentMethod.Name, True)
Finally
If conn.State = ConnectionState.Open Then
conn.Close()
End If
End Try
dbMessages = cmd.Parameters("p_message").ToString
End If
arrStatusMessages.Add("Retrieved Oracle Data Successfully")
End Sub
' Original Implementation ; No longer used
Public function GetOracleData
Dim conn As New OracleConnection
conn.ConnectionString = dbconn.Connectionstring
Dim cmd As New OracleCommand
With cmd
conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("MyConnectionString").ToString
cmd.CommandText = DATABASE.GetSalesData
cmd.CommandType = CommandType.StoredProcedure
cmd.Connection = conn
End With
cmd.Connection = conn
Dim oparam As OracleParameter
oparam = cmd.Parameters.Add("p_businessdate", OracleDbType.Date)
oparam.Value = BusinessDate.ToString("dd-MMM-yy")
oparam = cmd.Parameters.Add("p_message", OracleDbType.Varchar2, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcSales", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcInventory", OracleDbType.RefCursor, ParameterDirection.Output)
Dim Adapter As New OracleDataAdapter(cmd)
Try
Adapter.TableMappings.Add("Table", Sales)
Adapter.TableMappings.Add("Table1", Inventory)
Adapter.Fill(dsOracleData)
dim dt as datatable = dsoracledata.tables("sales")
If IsDataNull(dt) Then
_errorType = DBErrorType.NullData
End If
If isDataEmpty(dt) Then
_errorType = DBErrorType.EmptyData
End If
_hasError = False
Catch oraEx As OracleException
_ExceptionText = oraEx.Message.ToString
_errorType = DBErrorType.OracleException
#If DEBUG Then
Throw oraEx
#End If
Catch zeroEx As DivideByZeroException
_ExceptionText = zeroEx.Message.ToString
_errorType = DBErrorType.DivideByZeroException
#If DEBUG Then
Throw zeroEx
#End If
Catch oflowEx As OverflowException
_ExceptionText = oflowEx.Message.ToString
_errorType = DBErrorType.OverflowException
#If DEBUG Then
Throw oflowEx
#End If
Catch argEx As InsufficientMemoryException
_ExceptionText = argEx.Message.ToString
_errorType = DBErrorType.InsufficientMemoryException
#If DEBUG Then
Throw argEx
#End If
Catch nomemEx As OutOfMemoryException
_ExceptionText = nomemEx.Message.ToString
_errorType = DBErrorType.OutOfMemoryException
#If DEBUG Then
Throw nomemEx
#End If
Catch Ex As Exception
_ExceptionText = Ex.Message.ToString
_errorType = DBErrorType.GenericException
#If DEBUG Then
Throw Ex
#End If
Finally
If conn.State = ConnectionState.Open Then
conn.Close()
End If
End Try
End class Error Class
Public Class Errors
Public Sub ExitClass()
Return
End Sub
' 'blnWriteNow says when Error is critical and no further processing needs to be done by class, then write to event logs or text files and call exit class
' to return control back to webpage. This is my first time trying this way.
Public Sub HandleError(ByVal friendlyMsg As String, ByVal objEx As Exception, ByVal methodInfo As String, Optional ByVal blnWriteNow As Boolean = False)
If Not blnWriteNow Then Exit Sub
Dim strMessages As String
strMessages = arrStatusMessages
'Send error email
If blnSendEmails Then
SendMail("[email protected], strMessages. applicationname, " has thrown error. ")
End If
'Throw error for debugging
If blnThrowErrors Then
Throw New Exception(strMessages & vbCrLf & objEx.Message)
End If
' Write to event log and if not available (shared hosting environment), write to text log
If blnWriteNow Then
If blnWriteToEvtLog Then
If blnCanWriteToEvtLog Then 'Program has write permission to log
WriteToEventLog(strMessages, _appname, EventLogEntryType.Error, appname)
Else
If Not Directory.Exists( appPath & "\log") Then
Try
Directory.CreateDirectory( appPath & "\log")
Catch ex As Exception
arrStatusMessages.Add("Cant't write to event log or create a directory")
End Try
End If
End If
End If
End If
End Sub
End ClassI have lots of stand alone stored procedures callled from .NET 20 programs that follow the following pattern. They runn against Oracle 10.2 on Win2003. The only deviiation is a couple where I insert to temptables. I specify a parameter for messages but don't know the best way to implement for Oracle as well as any tips on ODP.NET/oracle interactions error handling.
1. Is it recommended to implement exception handling in With Clauses?
2. If there is an exception in one cursor's SQL, how do I still execute the second?
3. Is it best in some circumstances to pass a null back to client and check for null in program?
From .NET programs I have run into a couple of problems.
4. TNS packet failure.
Anyways any suggestions or experiences are welcome.
CREATE OR REPLACE PROCEDURE GET_SALES_DATA
, p_businessdate in date
, p_message out varchar2
, p_rcSales out sys_refcursor
, p_rInventory out sys_refcursor
) is
open p_rcSales for
with somedata as (select ...)
, someMoreData as (selct ...)
-- Main select
Select * from somedata sd inner join somemoredata smd on smd.key = sd.key;
open p_rcInventory for
with somedata as (select ...)
, someMoreData as (selct ...)
-- Main select
Select * from somedata sd inner join somemoredata smd on smd.key = sd.key;
-- CODE NOT IMPLEMENTED
-- exception
-- when TOO_MANY_ROWS then select 'Error handling for future implementations' into p_message from dual ;
-- when NO_DATA_FOUND then select 'Error handling for future implementations. No data' into p_message from dual;
-- when others then raise_application_error(-20011,'Unknown Exception in GET_SALES_DATA Function');
-- WHEN invalid_business_date then select 'Invalid: Business date is in the current work week.' into p_message from dual ;
END GET_SALES_DATA;Pseudocode'ish because Module level variables and properties have not been defined here for brevity.
Public Class WebPage1
PAge_Load
GetData
End Class Data Access Layer
Public Class DAL
Public Sub GetOracleData()
Dim conn As OracleConnection
Try
conn = New OracleConnection
Catch ex As Exception
Throw ex
End Try
Dim cmd As New OracleCommand
With cmd
conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("MyConnectionString").ToString
cmd.CommandText = DATABASE.GetSalesData
cmd.CommandType = CommandType.StoredProcedure
cmd.Connection = conn
End With
cmd.Connection = conn
Dim oparam As OracleParameter
oparam = cmd.Parameters.Add("p_businessdate", OracleDbType.Date)
oparam.Value = BusinessDate.ToString("dd-MMM-yy")
oparam = cmd.Parameters.Add("p_message", OracleDbType.Varchar2, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rc_inven_csv", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcSales", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcInventory", OracleDbType.RefCursor, ParameterDirection.Output)
Dim Adapter As New OracleDataAdapter(cmd)
Try
Adapter.TableMappings.Add("Table", Sales)
Adapter.TableMappings.Add("Table1", Inventory)
Adapter.Fill(dsOracleData)
Catch ex As OracleException
HandleError("Exception Retrieving Oracle Data", ex, MethodInfo.GetCurrentMethod.Name, True)
Finally
If conn.State = ConnectionState.Open Then
conn.Close()
End If
End Try
dbMessages = cmd.Parameters("p_message").ToString
End If
arrStatusMessages.Add("Retrieved Oracle Data Successfully")
End Sub
' Original Implementation ; No longer used
Public function GetOracleData
Dim conn As New OracleConnection
conn.ConnectionString = dbconn.Connectionstring
Dim cmd As New OracleCommand
With cmd
conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("MyConnectionString").ToString
cmd.CommandText = DATABASE.GetSalesData
cmd.CommandType = CommandType.StoredProcedure
cmd.Connection = conn
End With
cmd.Connection = conn
Dim oparam As OracleParameter
oparam = cmd.Parameters.Add("p_businessdate", OracleDbType.Date)
oparam.Value = BusinessDate.ToString("dd-MMM-yy")
oparam = cmd.Parameters.Add("p_message", OracleDbType.Varchar2, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcSales", OracleDbType.RefCursor, ParameterDirection.Output)
oparam = cmd.Parameters.Add("p_rcInventory", OracleDbType.RefCursor, ParameterDirection.Output)
Dim Adapter As New OracleDataAdapter(cmd)
Try
Adapter.TableMappings.Add("Table", Sales)
Adapter.TableMappings.Add("Table1", Inventory)
Adapter.Fill(dsOracleData)
dim dt as datatable = dsoracledata.tables("sales")
If IsDataNull(dt) Then
_errorType = DBErrorType.NullData
End If
If isDataEmpty(dt) Then
_errorType = DBErrorType.EmptyData
End If
_hasError = False
Catch oraEx As OracleException
_ExceptionText = oraEx.Message.ToString
_errorType = DBErrorType.OracleException
#If DEBUG Then
Throw oraEx
#End If
Catch zeroEx As DivideByZeroException
_ExceptionText = zeroEx.Message.ToString
_errorType = DBErrorType.DivideByZeroException
#If DEBUG Then
Throw zeroEx
#End If
Catch oflowEx As OverflowException
_ExceptionText = oflowEx.Message.ToString
_errorType = DBErrorType.OverflowException
#If DEBUG Then
Throw oflowEx
#End If
Catch argEx As InsufficientMemoryException
_ExceptionText = argEx.Message.ToString
_errorType = DBErrorType.InsufficientMemoryException
#If DEBUG Then
Throw argEx
#End If
Catch nomemEx As OutOfMemoryException
_ExceptionText = nomemEx.Message.ToString
_errorType = DBErrorType.OutOfMemoryException
#If DEBUG Then
Throw nomemEx
#End If
Catch Ex As Exception
_ExceptionText = Ex.Message.ToString
_errorType = DBErrorType.GenericException
#If DEBUG Then
Throw Ex
#End If
Finally
If conn.State = ConnectionState.Open Then
conn.Close()
End If
End Try
End class Error Class
Public Class Errors
Public Sub ExitClass()
Return
End Sub
' 'blnWriteNow says when Error is critical and no further processing needs to be done by class, then write to event logs or text files and call exit class
' to return control back to webpage. This is my first time trying this way.
Public Sub HandleError(ByVal friendlyMsg As String, ByVal objEx As Exception, ByVal methodInfo As String, Optional ByVal blnWriteNow As Boolean = False)
If Not blnWriteNow Then Exit Sub
Dim strMessages As String
strMessages = arrStatusMessages
'Send error email
If blnSendEmails Then
SendMail("[email protected], strMessages. applicationname, " has thrown error. ")
End If
'Throw error for debugging
If blnThrowErrors Then
Throw New Exception(strMessages & vbCrLf & objEx.Message)
End If
' Write to event log and if not available (shared hosting environment), write to text log
If blnWriteNow Then
If blnWriteToEvtLog Then
If blnCanWriteToEvtLog Then 'Program has write permission to log
WriteToEventLog(strMessages, _appname, EventLogEntryType.Error, appname)
Else
If Not Directory.Exists( appPath & "\log") Then
Try
Directory.CreateDirectory( appPath & "\log")
Catch ex As Exception
arrStatusMessages.Add("Cant't write to event log or create a directory")
End Try
End If
End If
End If
End If
End Sub
End Class -
Javadoc @throws clause at a class level for all methods
hello
If all my class's methods throw the same RuntimeException for the same reasons, is there a way to put a @throws clause at class level?
I mean, I don't want to duplicate my comments for each of the methods I have. Say I want to add extra information... It would be a pain to copy paste same
comment for all the methods.
Thx in advance, any help welcomed :)kux wrote:
hello again
first of all, love your replay :). Nice to see people with good sense of humor :D
Ok, I made the story shorter. Of course I don't throw a raw RuntimeException. What I have is a subclass of RuntimeException. Basicly all my methods use a sql Connection and do a certain querry on a database. What I do is that I don't let checked SQLException propagate through my methods because the clients of the persistance layer should not be required to handle the low level sql exeptions.Correct!
Instead I catch them and rethrow them as DAOExceptions that SUBCLASS RuntimeException. Unusual... but... Hmmm... I can't say that's actually "bad practice", per se, but DAOException is traditionally a checked exception type thrown only from the very top of the DAO specifically so that clients must catch (or explicitly throw) it... Hmmm..
Basicly I used sun's DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html.
That's be The GOF's pattern... but yeah, good choice.
I made the question shorter because this is not the point. The question was about javadoc, not my programming practices :)But, but, but...
Ok... Ah... Ok.... Ummm, No. At least Not That I Know Of... BUT, what you can do is summarise your exception handling strategy once in the class summary section, and just reference it in each throws clause... you can stick intra-page links in java doc (I've seen them, just not sure how they're done, I think the syntax is something like {@link:anchor}... but that's just something I once saw somewhere... not gospel.
Also, if a method has throws DAOExceptions for an "odd" reason (like invalid data retrieved successfuly from the database (yes, it happens)) then you can still document that case in the method.
If your exception handling is really worth talking about then an external article referenced in the class summary. We use a wiki (http://en.wikipedia.org/wiki/DokuWiki) for such purposes, and many others including research schedules and papers, and (increasingly) design doco, even though that's outside the "official process" we find the wiki so much more convenient (i.e. searchable), especially since it's become possible to convert (simple) word-doc's straigth to wiki markup.
But, but, but... Programming practices are so much more interesting than documentation... who ever complained about in the documentation (besides me I mean).
Cheers mate. Keith. -
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 -
ADF Task Flow Exception Handling
Hi ,
I tried a very simple thing for taskFlow exception handling.
I created a bounded task flow with a page fragment (View1.jsff) and another view which is the TaskFlow ExceptionHandler (error.jsff).
The view1.jsff has a button whose action is bound to the backing bean. In the backingBean method I deliberately do division by 0.
Since this is an unHandled exception, I would have expected the control to come to error.jsff. But, instead I am shown a pop up box with the error message.
Why is the control not getting redirected to error.jsff ?
Thanks.
S.Srivatsa SivanHi Frank , im having the same problem.
I want to handle exceptions that occur while navigating task flows (example: A user navigates to a task flow that he/she does not have view permission)
I tried using a view activity and method activity as the exception handler but none of them works, the exception is still not handles. It does not even navigate to the exception handler on the task flow.
on the view page i have:
<af:panelStretchLayout topHeight="50px" id="psl1">
<f:facet name="top">
<af:panelGroupLayout layout="scroll"
xmlns:af="http://xmlns.oracle.com/adf/faces/rich"
id="pgl1">
Error message:
<af:outputText value="#{controllerContext.currentRootViewPort.exceptionData.message}" id="ot2"/>
</af:panelGroupLayout>
</f:facet>
<f:facet name="center">
<af:outputText value="#{my_exception_Handler.stackTrace}" id="ot1"/>
<!-- id="af_one_column_header_stretched" -->
</f:facet>
</af:panelStretchLayout>
I tried getting the error message and stacktrace from the controllerContext via EL like this "#{controllerContext.currentRootViewPort.exceptionData.message}"
and from the controllerContext class in functions that i have declared in my_exception_Handler class like this
" ControllerContext ctx = ControllerContext.getInstance();
ViewPortContext vCtx = ctx.getCurrentViewPort();
if(vCtx.getExceptionData() != null){
StringWriter stringWriter = new StringWriter();
PrintWriter printWriter = new PrintWriter(stringWriter);
vCtx.getExceptionData().printStackTrace(printWriter);
return stringWriter.toString();"
But all this dont even matter because when the exception occurs on the task flow it does not navigate to the default exception handler.
thanks for your interest and help in advance.
Cyborg_0912 -
Exception Handling In Struts, Declarative, programatic and customized excep
hello .
I'm workingon exception handling in struts , i executed the gobal exceptions.
In glabal exception handling , one will not get the root cause of exception , rather we print the message from resource bundle.
How to get the root cause of exception in jsp page.
Give me sample code to deal with ExceptionHandler claas.
Thank u
RoshuHi ,
I am in the same situation. Global exception is working fine in my struts application . But I need to show the exception stack trace also in the screen whenever the exception occurs.Can anyone please provide me a sample code to deal with ExceptionHandler class ?
Thanks in advance...
Regards,
BG -
Hi Friends,
This Exception handling is really causing some problems for me.I run a query,return the resultset,cook the data from my other java class and display it thru my jsp and the last statement from my jsp is to call the close method(commented out).The problem is if some unknown Exception arises the close() method is not being called,causing open connections which later on are
creating some disasters.I tried to implement it now using the finally method,so that it always gets closed,but hte problem is when i call the ReturnResultSet() method and try to cook the data,it says "ResultSet Closed".Please tell me which is the right way to implement this:
public ResultSet ReturnResultSet(String Query) throws Exception
try{
if (datasource != null) {
connection = datasource.getConnection();
if (connection != null) {
statement = connection.createStatement( );
resultset = statement.executeQuery(Query);
return resultset;
} catch (SQLException sqle)
sqle.printStackTrace();
return null;
finally {
try {
if (resultset != null) resultset.close();
if (statement != null) statement.close();
if (connection != null) connection.close();
catch (SQLException sqle) {
sqle.printStackTrace();
public void close()
try { resultset.close(); } catch (Exception ex) {}
try { statement.close(); } catch (Exception ex) {}
try { connection.close(); } catch (Exception ex) {}
*/Any help would be appreciated and some duke dollars would be awarded too.ThanksOk I think i got your point and i should award you
the duke dollars too,but one last thing to ask.I call
the close() method after all my processing is over,I
just
wanna know should I have the connection.close() thing
inside it,becuase dont that contradicts the whole
connection pool thing,as i am closing a connection
and it has to open a new connection for every
request.Or should i just have resultset.close() and
statement.close() in it.
Thanks for all your helpAre you talking about a standard J2EE container-provided connection pool? If so, then yes, you still need to 'close' the connection. That doesn't actually close it, it just tells the pool it is available to be used again the next time someone asks it for a connection. Hopefully you're not writing your own home-grown "connection pool". -
Exception handling for Scanner console input
I'm trying to add exception handling to a Scanner console to deal with exceptions caused by non-numeric input. My idea was to do use a try/catch in a for loop and break if no exception occurs.
Whats happening is the "iNumber = console.nextInt(); " does nothing on subsequent retries, when an exception occurs. That is, I enter "123w", an InputMismatchException occurs, goes into the first catch block, hits "continue" and goes back into the for loop, hits the "iNumber = console.nextInt(); ", then immediately blows through it without executing. Thus, I hit my max loop count and exit with iNumber = 0.
I'm thinking I may need to instantiate "static Scanner console = new Scanner(System.in);" again in the event of an exception?
Thanks for any feedback. I'm brand new at Java and learning as fast as I can :)
Here is the code:
class ConsoleInput
public ConsoleInput() // constructor
static Scanner console = new Scanner(System.in);
public int GetInput()
int iNumber = 0;
for(int i=0; i<3; i++)
try
System.out.print("Please enter a number: ");
iNumber = console.nextInt(); // get console input
break;
catch(java.util.InputMismatchException ex)
continue;
catch(Exception ex)
continue;
return iNumber;
}public class Scratch {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
boolean gotAValidInt = false;
int theInt;
System.out.println("Enter an int");
do {
try {
theInt = sc.nextInt();
gotAValidInt = true;
catch (InputMismatchException exc) {
System.out.println("Not an int. Try again.");
sc.next(); // consume the non-int that nextInt couldn't consume
} while (!gotAValidInt);
}There are different ways you could structure your loop, but the key is that when nextInt throws an exception, you have to call next() in the catch block to consume the token that nextInt couldn't.
Edited by: jverd on May 2, 2008 1:52 PM
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