Spring MVC Tutorials 19 - Form Validation 03 (more on Spring MessageSource concept...) Video Lecture | MVC Tutorials: Web Programming Course - Web Development

guys my name is I'm coach Gaurav and I
welcome you to come to series this
tutorial is in continuation with the
early one where we learnt all about form
validation fundamentals let me quickly
give you a brief overview of what we
learned so far in the previous tutorial
and subsequently we will learn all new
concepts related to form validation in
detail in this demo so let's start
because in the previous tutorial I
showed you two ways for customizing the
error message for size constraint which
we placed on top of student hobby
field the first way which we looked at
was you simply provide the custom error
message as an argument at the place
where you declare this size constraint
like this and the second way which we
looked at was you provide the custom
error message in a separate properties
file in your spring MVC project and for
that what I did in the previous tutorial
I included a properties file with the
name student messages in the project and
provided the custom error message for
size constant in that file for spring
embassy to consider this properties file
at runtime when any constraint violation
occurs I included this course snippet in
the springs clarification file in this
project with the school snippet I am
simply instructing spring MVC framework
here spring MVC framework in this
project I have included a properties
file with the name student messages at
runtime when any constant violation
occurs please consider this file to get
the customary message for that
constraint so after all these changes
now if I provide here some value in the
student hobby field which would violate
the size constraint which we have placed
on top of student hockey field and
summit the form the applique
is going to send back the same admission
form with this error message description
and the point to note here is this error
message which spring MVC is displaying
in case of size constraint violation is
actually coming from this properties
file as always which I just talked about
in a very brief manner I explained in
detail in the previous tutorial now
let's proceed further guys here in this
error message I would want you to
observe a very important point of hard
could it here three important values in
this error message the field name for
which I kept the size constraint min
value that is 2 and Max value that is 30
field name that is student hobby for
which I kept size constraint min value
that is 2 and max value that is 30 now
spring Avicii says developers this is
not so good way to keep all these as
hard-coded values in the error message
you know in future if some developer
would make a change in any of these
three values here in the student class
then he will need to make a change in
this error message to for all those
modifications which is not so good way
of programming so spring of a she says
developers in order to avoid this
situation in future you simply replace
these hard-coded values with these
placeholders that is 0 1 & 2 placed in
curly braces now after this change at
runtime when any user would violate the
size constraint which we have placed on
top of student hobby field then before
displaying this error message to the
user in the response web page spring MVC
framework would replace these
placeholders with the corresponding
values which we have provided here in
the student class it would replace 0
with the field name that
student hobby - with a min value that is
- and one with a max value that is 30
which we have provided here in the
student class guys let me quickly show
you this working on the browser and
subsequently I will explain more on the
changes which have just made in this
properties flat guys for Spring Embassy
to consider all the changes which we
have just made in this properties file
we got to restart the server so let's
stop the server and start it again good
so server is up again so after this
change now if I provide here some value
in the student hobby field which would
boil it the size constraint which we
have placed on top of student hobby
field and some at the forum let's see
what happens
cool the application sent back the same
admission form with this and method but
the point to note here is before
displaying this error message in the
response webpage spring amra c replaced
all these placeholders with the
corresponding values which we have
provided here in the student class so
far so good now there are a couple of
important points which you should note
here for all the changes which we just
made in this properties file as I just
showed you the concept of placeholders
which we provided here in the custom
error message or size constraint but in
general while using such placeholders in
any other custom error message in this
properties file for any other constraint
you please follow these simple
guidelines
now one last an important concept guys
in this demo if you remember I had to
restart the server after I may change in
this
but is filed for spring am you see to
consider it now string MZ says he
developers if you do not want to restart
the server every time you make a change
in this properties file then you simply
go to the springs configuration file in
your project and add this statement in
the message source being with this
statement I am simply instructing spring
a Massif email history embassy framework
at runtime you please load all the
changes which anyone is making in this
properties file after every one second
guys I would recommend using this
feature only in the development
environments and not in the production
in one because this feature may degrade
the performance of application so use
the switcher only and only if it is
needed otherwise don't use it in your
application in the next tutorial we
learn bout some more form validation
annotations like ordinal not empty past
future etc etcetera
long looking at some more concepts
related to fall validation there is a
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