Tuesday, December 13, 2016

Use one lookup table as base for all the LOV's

One lookup table as base for all the LOV's

Lists of Values ... it's probably one of the most often used components in APEX development. And actually in any kind of software development, I suppose.

Having an E-Business Suite background, I got the idea to steal one of the better ideas the EBS has and that's dealing with LOV's, "lookups" they're called.
All those lookups are based in one single table, operating over a lookup-type. In EBS a set of views is defined and those views are used depending on the EBS domain.
I choose not to go that far and kept it to one single table.

A second idea stolen from EBS is the dependancy between lookups. Also that idea I simplified a bit and I kept it to one level. Meaning a set of values can differ from the chosen value of another set.

Finally I used the idea behind the multi-lingual solution of the EBS. Though that is the one I simplified the most. Whereas in EBS you have a base table containing a code and an _TL table containing one line for each installed language, in this solution I simply maintain all languages in the same base table. All records have a language code and in most systems there are two, max three different languages.

Table structure

Let me run you first through some background info. This solution was built for an extension on the EBS, in the HR modules. But the customer has a whole different database setup for the APEX extensions, so we're not directly using the EBS itself. A daily routine copies some basic EBS data over to the "APEX db" using a database link.  The solution itself and the architecture has pro's and con's, but I'm not writing about that now, let's keep focus on the LOV's.

EBS uses a lot of LOV's and of course we want to offer the user the exact same LOV's in the APEX applications.
So the table EBS_GENERIC_LOVS was created.
  • LOV_TYPE: As explained in the introduction, the column LOV_TYPE refers to the type of LOV in EBS. It's basically the grouping name of the LOV;
  • LOV_CODE: that's the code used for the value itself. A code is unique within a type;
  • MEANING: is in fact the display value that goes with the LOV_CODE;
  • DEPENDANT_LOVE_TYPE and DEPENDANT_LOVE_CODE: it's the DEPENDANT combination of type and code. This links the value with a value chosen in another LOV. This LOV must of course exist and on the APEX page it must be entered before this LOV;
  • ACTIVE_FLAG, VALID_FROM and VALID_TO: the combination of these columns make the value available or not in the LOV;
  • LANGUAGE: a two-letter code for the language, depending on the language chosen in the application, it will show the correct value of the LOV;
  • SEQUENCE: an optional way to fix the ordering sequence in the LOV.

Language option

In case you're not familiar with EBS and how languages are being used up there: EBS is always installed in English (code 'US'). Optionally one or more other languages are installed, e.g. Dutch (code 'NL'). It's just a side note, because it has nothing to do with the solution itself. But it explains why screenshots show weird data :-)

When a user logs on to the EBS, a language is picked. That displays all the screens in that language. Also the data seeded by Oracle will be shown in the correct language.
But when you enter data, let's say the names of all the departments of your organisation, you initially enter that in one language. As Oracle can't translate that (yet???) in the other languages by itself, by default the entered value gets copied over to all different languages installed. And the user is responsible to and translate the values manually.
An example makes it more clear:

Two languages are installed: US and NL. A person that sets up the different departments is logged on in Dutch (code NL).
This person enters "Verkoop" as name of the sales department. When the SAVE button is pressed, two records are being saved in the _TL table for departments:
  1. Name: 'Verkoop' - Language: 'NL'
  2. Name: 'Verkoop' - Language: 'US'
Now it's up to this person doing setup to go and change the second line to:
  • Name: 'Sales' - Language: 'US'
If this step is not performed, every place where the department name is shown, regardless what language is chosen at login, the name 'Verkoop' will popup.

Dependant lists of values

This is exactly the same as what is done in APEX via Cascading LOV's. But here the link exists already in the table.
En example: the salary of an employee is identified by the grade that is defined for the employee. Each grade is split up in different steps (spinal points). The combination of a grade and a step (on a specific moment in time) define the salary.
This means the step (which is referred to as spinal point in the EBS) is dependant on the grade.
So every LOV_CODE of the type 'PER_SPINAL_POINT' will contain 'PER_GRADES' as dependant_lov_type and a specific value in dependant_lov_code. And that code of course must be a valid code for the type 'PER_GRADES'.


In APEX you still need to define the LOV's that belong to the specific page items.
But this is where you gain from this solution. Because all your LOV's will look the same. It's a simple query every time on the same table:

As you can imagine, the language is stored in the application item AI_LANGUAGE.
The columns description and meaning are often mixed in EBS, hence the NVL.

On every LOV_TYPE you can make an APEX LOV with this same query as base. The only thing different will be the where clause "lkp.lov_type = ".

The dependant LOV identifying the step will then look like this:

The result in APEX

You notice that although the application language is English, the content - in this example the names of the grades - is in Dutch. This is - as explained above - because in EBS the (manual) translation of the setup of the grades from Dutch to English was never done!

Because Step is depending (cascading) on the Grade, no value can be selected as long as the Grade hasn't been entered:

Once a grade is chosen, the dependant values in Step appear:

My conclusion

This solutions requires hardly no extra effort compared to the standard way of working.
I would say even less effort is required.
On top of that it is absolutely no stopper of any existing LOV already in the system.

But most important advantage: I described the link with EBS, but in general it can be used for any system you link with: exactly the same LOV's on the base system can be re-used in the APEX application.

It should be clear that everything described above can also be done via normal LOV behaviour in APEX. But I truly believe that you will limit maintenance cost dramatically by using one single base table for all the LOV's!

Happy to share ....

Tuesday, December 6, 2016

Using JSON and Javascript to show or hide list menu entries

Using JSON and Javascript to show or hide list menu entries 

Here's a post that is the result of great team work. Proving once again a point that I believe in very strongly: so few great ideas come from the hand of just one person!

A colleague and I started brainstorming on this for a very specific need for a very specific customer. But our solution is really very flexible and re-usable for many other things! Read on, believe me, it get's interesting! ;-)

The technology

We're gonna use PL/SQL (of course), Javascript, APEX API's and a JSON structure.

What's our goal

We were looking for a flexible way to show or hide menu list entries. 

You see we have a dashboard alike application that does nothing else than kicking off other APEX applications. The complete set of applications is kind of a "Suite".
Now depending on which role you have in the organization you can see different list entries.
All very much feasible with the normal conditions of course.

But this "Suite" is growing and with the team working hard, a lot of applications are being build as others are ready to go in the Test or Acceptance cycle, others are ready for Production. But others are still "under construction" and aren't allowed to be installed in other environments.

The solution in words

So we wanted to have this double validation in a flexible way. The information - or setup if you want - needed to stay in the APEX application. We wanted to avoid storing it in a custom table, because then we would have the extra difficulty to maintain this "setup table" on al the different environments.

So we had a good close look at the application.
We also had a good close look at the List Entry screen in APEX and finally we browsed through the APEX API's.

The solution in technology

Administrator stuff

All the following points are to be done once, by an administrator. So of course, that part of the APEX application Suite is protected and only administrators can do it!

We're using a table to store the environment information. This will be a pretty stable situation.
In my neck of the woods, we often talk about the "OTAP" street. In the English speaking world, I think only the "O" needs explanation. 
The "O" stands for "Ontwikkeling", which is Dutch for "Developtment".
"T" = "Test";
"A" = "Acceptance";
"P" = "Production".

Our table looks like:

And a really simple APEX page to handle this setup information:

Then it gets a little more complicated. Or is that the wrong word? It should probably sound nicer when I say "interesting" ...

This overview page shows all the lists that we have identified:

And this information is fetched from the APEX repository. Have a look at the query behind the scenes.

We're gathering all the lists on the pages we've identified in the different applications.

And here it's important to picture that each and every menu groups some (Self Service) tasks to which you either have access to or you don't ...

Let's take a closer look at one single Menu, the one for "My Employees".
This is typically a menu that only is visible for managers ....

And now we land in a page that needs some explanation, I believe:

It's probably (hopefully) still clear that this is an overview of all the list entries of that List called "mijn_emp_en".
So we show the list entry name. Followed by the check icon if there is an APEX condition entered for that entry. In our example almost all entries have a condition.

Next are the four environments: O - T - A - P. It's simple enough: 'Yes' means that the list entry is to be displayed. Or in other words: this functionality is installed in that environment.
Because it's not sure yet it can be displayed according to the rules of role management!
That's the last column: "Enabled for these role codes".

Our roles are coded in a table as well. E.g. 'ADM' for 'Administrator' and 'DIR' for 'Director' ....

If you have a look at the screenshot above, you see e.g. that the functionality 'Leave cards' is only available on Development ('O'). And (e.g.) the 'Team occupation overview' is also available on 'T'. Nothing has been installed on 'A' or 'P' yet.
And all entries are allowed for that set of roles identiefied in the last column.

Now it's time to zoom in on one entry. And in the screenshot I changed the list of roles, to make it more clear:

First the condition in APEX is shown. Because this condition will also be checked upon. But in our exercise it was the idea to replace those conditions by this flexible mechanism.
We then chose the environments where the application can be used (remember - almost - every list entry navigates to another APEX application).

The functionality may not be shown for the roles 'CTRL' and 'EMP'. All other roles will be able to access it.

Behind the scenes, beyong the obvious

I told you, we're not storing the setup in a table, but directly in the APEX application.
The Apply changes button kicks off the process 'Save values for Envs and Roles'.
Here the two types of validations are seperated. Because we store them in the attribute values of the entry itself. 

This code was a bit of work. Figuring it all out. Therefor step by step:
  1. Gather all current values.
    A very important step, because we learned the API overwrites everything with null values if you pass nothing.
  2. A JSON structure is used.
    Simple: we needed "a" structure and we believe that JSON was the best way.
    One JSON for ENTRY_ATTRIBUTE_09 to store the environment Yes/No information.
    Another JSON for ENTRY_ATTRIBUTE10 to store the role code information.
    Here we used the apex_json package.
  3. Now we need to set the API mode to 'REPLACE'.
    To make sure we can put the mode back to the original value, first the original value is stored:
    l_old_api_mode := wwv_flow_api.g_mode;
    wwv_flow_api.g_mode := 'REPLACE';
  4. Next the API. It's is called: wwv_flow_api.create_list_entry
    See screenshot below, where most important parameters are highlighted.
  5. Set API mode back to it's original, which is reversing what we did in step 3.

Results in the List in APEX

To see the results, have a look at the Shared Component List

And we pick the "Team occupation overview"

And just to show the condition, always returning "false", obviously a test case ...

But the real interesting stuff is in the attributes:

Now this information is in this application's definition. And it can be moved to any other environment. It's not important that the functionality behind this list entry is in fact installed on that environment. Because it will only come into play when the environment specific setting is set to 'Yes'.

And at run time

Now we have all the setup available. We have all the information in place to decide what to display for whom and what not to display at all.

So let me first show two screenshots of the same application.
First one is the application seen by the eyes of an administrator (remember the 'ADM' as role).
Second one is by the eyes of a supervisor (remember the 'SV' as role).



To make this happen, we needed a Post-Rendering process on the page showing all the List regions:

It looks like a very simple process. But the complexity is hidden in the PL/SQL:

The PL/SQL code is too large to display here, but upon request (I guess) we're willing to share also that. However in short, this is what it does:

  1. Initialise some code:
  2. Check the DB we're living on:
  3. Loop through all regions, as some lists are defined in different applications, the query got quite large, but we're joining apex_application_page_regions and apex_application_list_entries
  4. Read both JSONs and look for the corresponding Y/N values
  5. We then check if we're at the end of a list, because if a list is completely empty, we also remove the region so you don't get a list region with no list entries in it!
  6. Check on the environment, because when the environment says no, we don't need to check the role condition, do we?
  7. Same check for the role
  8. Construct the javascript to remove the disabled list entries

Now, all this is executed as a JAVA script after having rendered the page. This means that an APEX condition is on a higher level than this validation. Meaning that if the APEX condition e.g. says 'Never' ... it really will be 'Never' and it will not display, no matter what comes out this Post-Rendering process.

Here we are ... a long explanation, I know. I tried several times to make it shorter, but then I believe the it was not possible to follow the route anymore. Well, I hope now it was possible to follow what we did. If it wasn't and you want to know more, I'm sure you'll find a way to get in thouch with me.

Also I want to thank again my colleague and partner in crime, Joost, for making this all possible!

Remarkable final thouch: we have some pretty good DJ's in Belgium: thanks Regi and Dimitri Vegas & Like Mike for the inspiring music while writing this all down .....

Happy to share ...

Wednesday, November 30, 2016

My advice is to use the Advisor

I have noticed (too) often when talking to other APEX developers, that the Advisor functionality is not well known.

Although this is also described in a lot of Best practice  guides, the functionality is in my humble opinion highly underestimated!

The APEX Advisor

I actually don't know how long it's been there, but it is quite some time.
And it's all standard and included in the APEX Application Builder.
It is to be found under Utilities.

It kicks off following popup window

I recommend to have a look at the section Checks to perform:

It may well be possible that you have opted for whatever reason to not follow one of the pre-defined rules of the APEX Development team. You can chose not to check on those rules.

Usually I advice to select all checks and read the advice of the Advisor. You can always opt of course not to do anything with one of the remarks. Because one thing must be clear: your app can run very fine with several Advisor errors or warnings in it. You do not need to fix them all. But it is advised to solve as many as possible and you may learn something from the best practises according to the APEX Development Team. They're smart people ... believe me ;-)

Depending how large your app is - of course - running the Advisor may take some time.
In the end it provides you with a clear overview and with the option to navigate directly to where you need to be to fix the problem.

The result filter

The filter comes in very handy to keep an overview or to focus on one specific type of error (or warning).

An advisor error

I'm not walking you through every possible error an Advisor can identify. 
For each error/warning the Advisor will give you an overview of what he thinks is wrong or can be done better.
With the View button you navigate directly to the place in your application that concerns this hit.

He doesn't know everything

An example of errors an Advisor run is always indicating is the following:

What the Advisor cannot see here, is that this "EVENT_LINK" is part of a specific template. It's not necessarily a real error. So these errors can be ignored.

So okay, here you go. Hope to have convinced some developers to start using it. It's really a good practice to run it at the end (or beginning if you prefer) of every working day!

Happy to share ....

Tuesday, November 22, 2016

Interaction between two date fields made visible upon data entry

Interaction between two date fields

Have you ever been in a situation where you have two date fields and the second one is dependant on the first one? Sure you have!
Every time you do something with a start- and end-date ...

It's so very logic that the end-date must be later than the start-date. As long as we can't travel in time, this is a certainty.


As often, my examples originate from the HR field.
This example is a page in an APEX app that gathers information for a candidate employee.

The candidate category was identified as 'Fixed Term', which implies you have to provide a start-date and an end-date for the contract.
We're gonna focus now on the Date start and on the Date end.

In the example used, the Date start must be a date in the future. The Date end must be later then the Date start.

When you do nothing

It's obvious, when you do nothing, you allow input of all dates.

I'm writing this blog post on November 21st. You can see I'm allowed to enter a date in the past for a Date start:

Same thing for the Date end. Even worse: I'm allowed to enter (pick) a date before the Date start:

Which results possibly in something like this:

What about validations?

Yes, of course, you can use validations to force the user in entering the correct dates. But those validations are executed on page submit. That's a bit too late, don't you think? So read on, it gets interesting now!

Known and standard features of APEX

To start of, we're gonna use a standard APEX feature to make sure the Date start is a future date.
A small notice here: a "future date" in a data entry application may not be clear enough as a spec. Because when reading "future", it will be checked against the system date. So when entering a date today, save the information and update it tomorrow, this system date has obviously changed. So make sure you get the intention of your customer clear! In our example we simplify and acknowledge that we're validating purely against the system date.
First identify the Date start:

Go to the property panel and have a look at the Settings section:

Three options here: Highlighted date, Minimum date and Maximum date. They all operate similarly. Actually the APEX Help explains it quite clearly:

We're now making sure that we highlight the current date (sysdate +0 days).
Same for the minimum date. It will make sure that you cannot pick a date in the past!
Yes!! One down.

We're now at this stage:

You're unable to pick a date in the past!

Also note some other interesting properties for datepicker fields, like e.g. the Show other months (Y/N) property. I suggest to try them out, but it's not the subject of this post ...
You can now do the same for the Date end. However, it will only enforce the user to pick a date in the future. What if the Date start is entered for December 1st (remember, the system date right now is November 21st)? You can still enter November 22nd for the Date end. Not what we want!

Full solution step by step

We're gonna use some javascript coding to make the relation between the Date start and the Date end
However it's been coded in a way that it can be any two date fields on the same page.

Page level functions

In the page properties, navigate to the JavaScript section.

Two functions need to be included here:

function stringToDate(_date,_format,_delimiter) {
    var formatLowerCase=_format.toLowerCase();
    var formatItems=formatLowerCase.split(_delimiter);
    var dateItems=_date.split(_delimiter);
    var dayIndex=formatItems.indexOf("dd");
    var monthIndex=formatItems.indexOf("mm");
    var yearIndex=formatItems.indexOf("yyyy");
    var month=parseInt(dateItems[monthIndex]);
    var formatedDate = new Date(dateItems[yearIndex],month,dateItems[dayIndex]);
    return formatedDate;

function setMinAndMaxDates( fieldnameStartDate, fieldnameEndDate, maximumLengthInYears) {
    var minDateAsString = $x(fieldnameStartDate).value;
    var selectorEndDate = apex.jQuery("#" + fieldnameEndDate);

    if (minDateAsString == null || minDateAsString == '') {
        selectorEndDate.datepicker("option", "disabled", true);
    else {
        var minDate = stringToDate( minDateAsString, "dd-mm-yyyy", "-");
        // Determine maxDate by adding given amount of years to minDate:
        var maxDate = new Date(minDate);
        maxDate.setFullYear(maxDate.getFullYear() + maximumLengthInYears);

        selectorEndDate.datepicker("option", "minDate", minDate);
        selectorEndDate.datepicker("option", "maxDate", maxDate);
        selectorEndDate.datepicker("option", "disabled", false);

The first function (stringToDate) will need to hold the date format that you use. Generally accepted in my neck of the woods is the format "dd-mm-yyyy". So you will need to adapt this to your own setting. Or when you allow the user to pick the date format in a preference page, you will need to make this function more flexible as well!

The second function (setMinAndMaxDates) will actually add the needed attributes to the page items on the fly.
As you can see, the function accepts 3 parameters. The fieldnameStartDate and fieldnameEndDate refer to the page items you want to refer to. This makes the use of these functions very flexible. And you can just copy and past it over to any other page in your app.

Dynamic action doing the magic

As so often is the case, here again the dynamic action will do the magic!
In the use case described here, "something" will need to happen to the Date end when a date is picked in the Date start.
Logically the On change dynamic action is used on the Date start.

Following properties are set on Dynamic action level:

And because the functions are coded generically, the javascript in this TRUE action remains extremely simple:

setMinAndMaxDates("P3_DATE_START", "P3_DATE_END", 10);


This results in following behaviour:

Date start

As soon as you pick a date in the Date start datepicker, the Date end gets defaulted to the same date.

Date end

No dates can be picked before the Date start.
Here you go .... all done !!!

Oh no ... there is a "but" 

Yes, the user gets guided perfectly when using the datepicker. But he can still pick a date and then change it manually!

My conclusion

So it doesn't take away all your pains. But it does support your user in the best possible way. And because that user can still manage to make things wrong, you should also provide the validations on page submit.
But I hope you agree with me that it is a nice way to help the user with the data entry.


For this blogpost I must specifically thank my colleague Joost Hoevers, as he has coded the nice solution and made it perfectly re-usable! 

Thank you, 

Happe to share!