Skip to main content

Transform ORA-xxxx messages into something more user friendly in APEX

When you delete a record that is referenced using a foreign key constraint you get a rather ugly error like this:
Of course you can prevent such a thing from happening by creating a Page process that checks if your delete is "Ok". But that's double coding...and dangerous when you have to maintain your database structure: You'll probably forget to update the processes as well. Wouldn't it be nice if you can 'catch' that error an present it to the end user in a more friendly way (and with a somewhat more understandable text)? I guess your users will be more enthusiastic about your application (and you) when you show them something like this:
So how do we achieve that?

1. Edit the "Error Page Template Control" region of your Application Default Page Template, because that's the one that is used for presenting errors. Set it to :

<script type="text/javascript">$(document).ready(function(){raiseErrorHandler();});</script>
2. Create the raiseErrorHandler function (I'll use some jQuery UI stuff to show the nice dialog box):

function raiseErrorHandler(){
vError = $(".ErrorPageMessage");
vError.hide();
var get = new htmldb_Get( null, $v('pFlowId')
,'APPLICATION_PROCESS=GetErrorMessage'
,$v('pFlowStepId'));
get.addParam( 'x01', vError.html());
gReturn = get.get();
get = null;
var errArray = gReturn.split("#",2);
showError( vError, errArray[0], errArray[1]);
}

function showError(pThis, pTitle, pText){
vText = '
'+'
'+pText+'
'
$(pThis).append(vText);
$("#alert").dialog({
bgiframe: true,
modal: true,
minHeight : 200,
width : 600,
closeOnEscape : false,
close : function(){window.history.go(-1)},
buttons: {
Ok: function() {
$(this).dialog('close');
$("#alert").remove();
window.history.go(-1);
}}
});
}
3. That Javascript function calls an Application Process GetErrorMessage:
DECLARE
p_error_title varchar2(32767);
p_error_text varchar2(32767);
p_ora_error varchar2(32767);
BEGIN
p_ora_error := wwv_flow.g_x01;
-- Get "translated" error message
get_error_message( p_ora_error, p_error_title, p_error_text );
htp.p( p_error_title||'#'|| p_error_text );
END;
4. The procedure get_error_message is defined in the database. This procedure queries a table that contains the contraint name (the 'ORA Error') and a more user friendly description.

create or replace PROCEDURE GET_ERROR_MESSAGE
( p_ora_error IN VARCHAR2
, p_error_title OUT VARCHAR2
, p_error_text OUT VARCHAR2
) AS
CURSOR c_mps IS
SELECT code, description
FROM afk_message_properties
WHERE INSTR( p_ora_error, constraint_name ) > 0;
BEGIN
OPEN c_mps;
FETCH c_mps INTO p_error_title, p_error_text;
CLOSE c_mps;
EXCEPTION
WHEN NO_DATA_FOUND
THEN
p_error_title := 'No translation found for this error';
p_error_text := p_ora_error;
END GET_ERROR_MESSAGE;
The Application Process spits out a concatenated text, that will be segregated again in the Javascript function. The result is presented to the user in a way that would make him happy....
Even if there is no error definition found in the table, the error will be shown in the dialog box - only the translation to a normal language is missing.

Kinda cool I think!
You can see a public demo when you click here.
38 comments

Popular posts from this blog

Refresh selected row(s) in an Interactive Grid

In my previous post I blogged about pushing changed rows from the dabatase into an Interactive Grid. The use case I'll cover right here is probably more common - and therefore more useful!

Until we had the IG, we showed the data in a report (Interactive or Classic). Changes to the data where made by popping up a form page, making changes, saving and refreshing the report upon closing the dialog. Or by clicking an icon / button / link in your report that makes some changes to the data (like changing a status) and ... refresh the report.  That all works fine, but the downsides are: The whole dataset is returned from the server to the client - again and again. And if your pagination size is large, that does lead to more and more network traffic, more interpretation by the browser and more waiting time for the end user.The "current record" might be out of focus after the refresh, especially by larger pagination sizes, as the first rows will be shown. Or (even worse) while you…

Dockerize your APEX development environment

Nowadays Docker is everywhere. It is one of the main components of Continuous Integration / Continuous Development environments. That alone indicates Docker has to be seen more as a Software Delivery Platform than as a replacement of a virtual machine.

However ...

If you are running an Oracle database using Docker on your local machine to develop some APEX application, you will probably not move that container is a whole to test and production environments. Because in that case you would not only deliver a new APEX application to the production environment - which is a good thing - but also overwrite the data in production with the data from your development environment. And that won't make your users very excited.
So in this set up you will be using Docker as a replacement of a Virtual Machine and not as a Delivery Platform.
And that's exactly the way Martin is using it as he described in this recent blog post. It is an ideal way to get up and running with an Oracle database …

apex_application.g_f0x array processing in Oracle 12

If you created your own "updatable reports" or your custom version of tabular forms in Oracle Application Express, you'll end up with a query that looks similar to this one:
then you disable the "Escape special characters" property and the result is an updatable multirecord form.
That was easy, right? But now we need to process the changes in the Ename column when the form is submitted, but only if the checkbox is checked. All the columns are submitted as separated arrays, named apex_application.g_f0x - where the "x" is the value of the "p_idx" parameter you specified in the apex_item calls. So we have apex_application.g_f01, g_f02 and g_f03. But then you discover APEX has the oddity that the "checkbox" array only contains values for the checked rows. Thus if you just check "Jones", the length of g_f02 is 1 and it contains only the empno of Jones - while the other two arrays will contain all (14) rows. So for processing y…