Spring MVC Tutorials 07 - writing an annotation based controller class -@Controller; @RequestMapping Video Lecture | MVC Tutorials: Web Programming Course - Web Development

guys my name is Akash Gaurav and I
welcome you to on to series in the
previous tutorial I created a basic web
application using spring MVC framework
by following these simple steps we
looked at each step in detail along with
each component which you are seeing here
in this spring MVC workflow diagram
spring MVC says there are two ways of
writing a controller class in your
application one ways without using
annotations like this and the other ways
using spring MVC provided annotations so
far we developed this application using
the first way that is without using
annotations now I'm going to talk about
how to write the same controller class
using annotations that is the second way
so let's start without wasting much time
let me state forward modify this non
annotation based controller class with
the equivalent annotation based
controller class and later I'll explain
everything in detail so this is the
equivalent annotation based version of
hello controller class which we
previously wrote with the non annotation
based approach spring MVC says if you
mention controller annotation on top of
a Java class then I will consider it as
a sprint controller there are two
benefits of using this annotation
approach first benefit is you do not
need to extend the hello controller
class from any specific base classes or
implement any specific interfaces as I
did in the previous tutorial while
developing the non annotation based
hello controller class and the second
benefit of using this annotation on top
of a controller classes you do not to
put its entry here in the spring
dispatches of latex
five you can simply remove it from this
file so what's the idea the idea is very
simple if you write controller class
using controller annotation then you are
free from writing its entry here in the
XML file but if you are writing the
controller class using a non annotation
based approach as I did in the previous
tutorial then you need to put its entry
in the XML file this is an important
thing to know about this feature spring
says if you want to make use of this
feature then you have to place this
entry in this XML file here I'm simply
telling Spring Framework here spring MVC
framework please automatically detect
all java classes having controller
annotation written in them which are
placed in this package and also please
do consider all of them as if I have put
their entries in this XML file if you do
not write this statement here in the XML
file then you will need to put an entry
of every single controller class in this
file as we did in the previous tutorial
even if all are written using controller
annotation here so this is just a handy
feature which you have enabled in your
application by providing the components
can statement here in the XML file which
will just make your code a little
cleaner and with less number of lines of
code this one more could use now you do
not need to provide an entry of a handle
mapping class here in the XML file also
so I will simply remove it now coming
back to the hello controller class again
what's this request mapping annotation
doing over here what's it all about guys
this is a very important concept which
I'm going to tell you now and I would
need a little more tension of yours to
understand
that when the request reaches to the web
dot XML file from a crimes processor the
request is mapped to the dispatcher
servlet or front controller of spring
MVC framework the front controller reads
this file for further processing the
request after seeing this statement here
in the XML file the front controller
understands that you have used
annotation based controllers in the
project in this package so the first
thing it does is it loads all those
controller classes in its memory now it
has to decide upon which controller
method it would invoke for further
processing the request and how it does
is it looks at the request mapping
annotation value of each method present
in each controller class in the
application and compares their values
with the incoming requests you are a
pattern and whichever request mapping
annotation value matches with the
incoming request URL pattern it simply
makes a call to that method in this case
if a user has requested for a webpage
using this URL then front controller
would make a call to this method after
finding that it's your pattern is
matching with the request mapping
annotation value of this method alright
so now you know the meaning of request
mapping annotation to this method would
simply prepare the model and view object
which is having the data which is to be
displayed on the response webpage and
the view name which front controller
would use to prepare the response so
this method would send this object back
to the front controller the front
controller now would find out the exact
part of the view which is present in the
project using the view resolver class
and this we talked about in detail in
the previous tutorial so for this case
it finds out that it has to make a call
to hell
peyt dot JSP file for further processing
the request and this file simply mixes
the data which hello controller class
has provided to it along with the HTML
code and prepares the response using
this mixture and sends it back to the
front controller the front controller in
turn sends the response prepared by
halibut or ESP file to the clients
browser so the request cycle is
completed this way let's quickly run the
project on the server and test it so the
project is running in the server open
the browser and place this URL click
enter cool the application that we
developed using annotations responded in
the same way as it responded without
using annotations guys in this tutorial
I presented things at a very basic level
and talked about just a few annotations
that you can use in a controller class
in the next tutorial I will talk about
more about request mapping and other
annotations supported by spring MVC
framework I thank you for liking my
tutorials if you have any queries or
feedback just provide them below the
video or simply write to me on this ID
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MVC series do not forget to mention that
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I'm going to catch you in my next
tutorial