Spring MVC Tutorials 14 - Data Binding with a User-Defined Type; BindingResult (concept) Video Lecture | MVC Tutorials: Web Programming Course - Web Development

guys this tutorial is in continuation
with the earlier one where I talked
about how spring embassy automatically
binds HTML form data which is submitted
by the user on the browser with the
corresponding properties of the student
object if you observe here up till now
I showed you this Auto data binding
feature working with all properties
present in the student class having
built-in types like string long date
error list now question is can you use
this feature for a property which is
present in the student class having a
user defined type or it let me explain
you this way what I'm really talking
about what if I add a new class in the
project with the name address having
these properties country city street and
pin code along with getters and setters
methods and in the student class I would
add a new property with the name student
address which is having address as its
type along with it scatters and setters
methods a question is can you use the
auto data binding feature which is
provided by spring mu Z for this
property as well which is having I use a
different type that is address and the
answer is yes let me make all necessary
changes in the admission form dot JSP
file and admissions success torch SP
file related to this property and later
I'll explain everything to you in today
good so I'm done with making all
necessary changes in admission form
gorgeous B file an admissions success
tortures P file related to this property
which has just added in the student
class now let us understand in detail
what I've really added in these two
files hearing the admission form
dodgiest B file have added four new form
elements country city street and pin
code with input type as text does not
this is an important thing to learn over
here spring MVC says if you want me to
automatically bind a particular form
elements value with a corresponding
property of student class having a user
defined type the way we have student
address property over here having
addressed as its type then you mention
the form elements named in the GSP file
with this property name dot the
corresponding property of its type and
that's why you are seeing here me
writing student address dot country
student address dot city student address
start street and student address dot
paint code so here but the user would
submit this form on the browser spring
MVC will automatically bind this student
address dot country form elements value
with a country property of this student
address property similarly spring MSE
will automatically bind this student
address dot city form elements value
with city property of student address
property
unlike face it will bind these all of
the form elements values with the
corresponding properties of student
address property I hope you got the
point and here in the admission success
rod just be file I've added this code
snippet so as to display the user
entered
use for country city street pin-code
form elements along with other form
elements values on the response web page
after user submits ignition form on the
browser guys let me show you this
application working on the browser and
consequently I'll explain more about the
changes which have just made in this
project now after all this changes when
a user would type this URL on the
browser and hits enter my application
will send this web page as a response
back let's say the user provides these
values into these form elements however
the user would click on this summit
button the request will reach to this
request handler method and here this
model attribute annotation would
automatically bind all these form
elements values with the corresponding
properties of this student object and
immediately after this Auto data binding
task spring MSE would make a call to
admission success tortious be filed in
order to produce the final response
using this code snippet let me submit
this form and show you this working cool
my application sent this web page as a
response displaying all user and dead
values in the HTML form including the
property values for student address that
is country city street and pin code as I
just showed you how you can use spring
MVC is provided auto data binding
feature with a user defined type now
let's proceed further and talk about one
of the most important and fundamental
concepts related to data binding and
that is the concept of finding errors as
in all appropriate spring MVC tutorials
I've laid stress on one point that the
auto data binding feature which is
provided by spring MC is like a magic to
us developers kind of write less code
and do more things with the help of
this feature but you know sometimes due
to some extra set reasons spring MC just
fails to bind the data which is coming
all along with incoming requests with
the intended property or properties of
the corresponding object let me show you
with an example of for Trillium talking
about here for this student ruble form
element what if I provide here some
value other than the numbers say I
provide here a value ABCD and click on
submit button
oops it just failed for this case my
application sent an error of a page
which is just displaying me this
description of the error occurred on the
server the request sent by the client
was emphatically
incorrect the reason for this
application failure is very simple and
clear here I provided ABCD as a value
for student mobile form element and when
I submit in the form spring mu C tried
performing auto determining task and
while performing this task
it tried converting ABCD value for
student ID form element into the type
long and it cannot do so because you
cannot convert an on number into a long
type and because of that reason sake
when I submitted the form it just threw
this error webpage guys I just showed
you a very simple use case for which
spring MVC failed while performing the
data binding task and through this error
wattage likewise there could be many
other reasons for data binding failure
at runtime so question is how developers
should deal with such a situation when
in data binding related error occurs on
the server the most common pattern which
developers follow to deal with such a
situation as they return back the same
HTML form to the client along with the
complete description of data binding
errors so that the user would refill
HTML form with all correct values and
submit that table form back to the
spring MVC application so now question
is how will achieve such a kind of
pattern in this project spring MVC says
he developers I have something called as
binding result and if you place the
binding result on the method argument
for this request handler method like
this that is immediately after model at
you would an addition the way I placed
here then I would catch all binding
related errors appropriately for you and
put all of them into this result a
reference spring msec is in addition to
using binding result of a are placed
over here you add this course snippet in
this request handler method which is
simply returning back the same HTML form
that is admission form broaches we fell
back to the client as a response if any
data binding related error occurs on the
server this is one more change which we
have to make in the admission form got
GSP file here you add the errors tag
which is provided by spring MC the way I
have used over here it's job is to
simply display the complete information
about the binding related errors which
will occur on the server to the client
in order to use this every stag which is
provided by spring embassy you got to
add this statement on top of this web
page that is you need to include this
tag library the way I have included here
I'll do one thing I will quickly show
you this application working on the
browser with all these modifications
which are made in this application and
then I would explain the complete
workflow once again for all the changes
which have just made now after all these
modifications if I would sum it the same
form for which I entered here wrong
value for student mobility
there is a non number value what would
happen let's check it out cool this time
my application sent the same HTML form
back because of
this code snippet that I've added over
here and because of this errors tag
which are placed over here on top of
this chesley file my application sent
here the complete description of binding
related error which occurred on the
server for this form because here in
this tutorial I just meant to introduce
you to the concept of pining result and
how you would send the same HTML form
back to the client the time of any
binding related error which would occur
on the server I'll talk more on binding
result and related concepts
whenever talk on form validation
features provided by spring MVC
in the next tutorial I'll show you how
developers can have more control over
Auto data binding feature which is
provided by spring MVC as a big thank
you for liking all of my tutorials on
spring MVC series if you have any
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