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  1.  Home
  2. WEB400
  3. March 2018

Re: Rise of Node

Tim,

I have in my framework 3 types of client validation:

The simplest one is that i have "codelist" of values that applys to a field
e.g. a status field,
this stored in a table with fieldname,codevalue, description and is
transferred in the UI like
a drop down but may be validated by a generic service program.

The next level is small referential files, there i generate a little
service program that returns
values and descriptions than i then include in a drop down in the UI.

The last is a drop down in the UI that is connected to a REST service. The
service may retyurn
either a single row based on keyfield, a number of rows based on a search
criteria or the whole
table if no keyvalue or search criteria is given.

In the UI i look for key-strokes in the drop down field and more than
to-tre char. starts the automatic
search routine.

Since these type of fields are mandatory there is no way the user can skip
them in the UI.

If not entered the send buttom are deactivated and the field is marked with
an error message

.

On Sun, Mar 18, 2018 at 4:53 PM, Tim Fathers <X700-IX2J@xxxxxxxxxxx> wrote:

...typically we do, but Nathan's question implied that the validation he
was concerned about involved chaining to files, hence more complicated than
simple client side validation. My examples perhaps weren't the best...!

________________________________
From: WEB400 <web400-bounces@xxxxxxxxxxxx> on behalf of Henrik Rützou <
hr@xxxxxxxxxxxx>
Sent: 18 March 2018 16:29
To: Web Enabling the IBM i (AS/400 and iSeries)
Subject: Re: [WEB400] Rise of Node

Tim

why not just let the client validate simple field values?

On Sun, Mar 18, 2018 at 4:24 PM, Tim Fathers <X700-IX2J@xxxxxxxxxxx>
wrote:

The short answer is that you'd either have a WS API to validate each
field, or roll it all into one which is able to validate individual
fields,
sets of fields or the whole lot. For example:
/my-web-service/validate_customer_name {name: 'Martin', surname: 'Gore'}
/my-web-service/validate_customer_address {addressLine1: '1 Basildon
Lane'...}
or
/my-web-service/validate_customer {name: 'Martin', surname: 'Gore',
addressLine1: '1 Basildon Lane'...}

In my framework, these APIs are just stored procedures that you can
implement in SQL or RPG or whatever else you wish. They just do the same
thing you'd do in your original RPG (with some caveats - see below), in
Node you'd have to implement that
functionality in Javascript/Typescript and SQL (as the database I/O is
asynchronous, you wouldn't end up blocking the Node thread so there would
not be an issue in that respect). The result would be either an HTTP
status
code of 200 OK or 4xx to indicate an error, and in the body of the
response
you would provide details of the error(s) that occurred so that the front
end can display something nice to the user. Of course, this sounds slow,
and in relative terms it is (and that's without thinking about some of
the
other overheads involved I mention below), but in reality we get average
round trip times in the low 10s of milliseconds for such requests which
is
quite incredible when you think about what is going on. Even if it were
slower it wouldn't matter that much because you could have your web app
fire off the validation when the input field loses focus, that way the
user
can carry on filling the form and when the validation result comes back
you
can display the resulting m
essage and highlight the field etc. This still gives near instant
validation as the user moves through the form, which is a big improvement
over the green screen.

On paper, things look a lot worse than you might imagine from a
performance perspective. Because of the stateless nature of RESTful web
services you incur a fair bit of overhead with every web service call
that
you typically wouldn't have in a green screen application. For example,
figuring out who the user is that's executing the call (by decrypting
some
sort of token), determining what the user's rights are to the API and
perhaps to the data too, validating the inputs (on every call because you
can't trust the client), dealing with optimistic locking (because you
cannot lock rows for update), dealing with paging etc. etc. In practice
however, as I mentioned, it's extremely fast, even the paging queries we
use take no more than a couple of hundred milliseconds to run over a file
with the right indexes.

________________________________
From: WEB400 <web400-bounces@xxxxxxxxxxxx> on behalf of Nathan Andelin <
nandelin@xxxxxxxxx>
Sent: 18 March 2018 05:40
To: Web Enabling the IBM i (AS/400 and iSeries)
Subject: Re: [WEB400] Rise of Node

On Sat, Mar 17, 2018 at 7:09 AM, Aaron Bartell <aaronbartell@xxxxxxxxx>
wrote:

Is there really a case to be made for Node doing it all?

In my mind, yes.


Say you have an application with a form that prompts for eight (8)
fields,
each of which is a surrogate key reference to eight separate tables.
Validating the form requires the application to ensure that the eight
values submitted on the form must exist in eight separate tables. What
would the JavaScript look like? How would it perform? How long would the
user be waiting for a response saying that the input was successful?

Frankly, I'm skeptical about Node handling that type of validation and
returning appropriate (sensible) messages to users.
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