Spring MVC Tutorials 29 - Exception Handling 02 Video Lecture | MVC Tutorials: Web Programming Course - Web Development

guys my name is incacha Karev and I
welcome you to gone to series in the
previous tutorial we learnt about some
of the important fundamentals related to
exception handling feature so overall
what we did we first included these
three customized ANOVA pages under the
by nerve folder and here in this
controller class we included these three
exception handler methods so now after
making these changes here when a user
requests for this webpage and while
processing this request if this
controller method throws a null point
exception spring MVC framework makes
equal to this exception handler method
and it turns null pointer exception dot
GSP as a response back to the clients
browser and for all cases when this
mother throws an i/o exception spring
MVC framework makes equal to this
exception handler method and he turns IO
exception dot gsv and for all cases when
this method throws an automatic
exception for which we do not have any
specific exception handler method
defined in this controller class spring
MVC framework simply makes a call to
this generic exception handler method
means an exception handler method with
exception block class passed to it as a
parameter and it turns exception brought
USB as a response so the overall concept
which we learned so far is very very
simple and clear while processing a user
suppress if a controller method throws
an exception spring MVC framework simply
looks for an appropriate exception
handler method in the same controller
class if it finds such a method it
simply makes a call to that otherwise it
returns the default error of a page back
to the clients processor as a response
and all this we learned in detail in the
previous tutorial now let's proceed
further
because the only drawback of the
approach we learned so far is an
exception handler method is applicable
only to the controller class where it is
present and cannot be applied or used by
framework for exceptions thrown by other
controller classes so what it means
let's say in your application you have
ten controller classes and for each
controller class you want to handle a
null pointer exception so with this
approach you will need to include an
exception and a method for null point
exception in each of ten controller
classes separately so the kind of
approach we have learned so far you
might end up adding a lot of redundant
exception handler methods in our
controller classes so is there any way
that we could write an exception and a
method for null pointer exception only
at one place which applies to all
controller classes which are present in
the application yes there is a way
spring MVC framework says hey developers
you include a class in your application
with controller advice annotation on its
top then whatever exception handler
methods you put in such a class all
those would be applied to all controller
classes which stays in the application
let me show you this concept working so
here I have added this new class with
the name global exception handler
methods which has controller advice
annotation on its top so now according
to the concept which I just told you
whatever exception handler methods I
would place in this class all those are
applicable to all controller classes
which stays in this application so what
I'll do I'll take off all these
exception handler methods from this
controller class and put all of them
here at one place means in this
controller advice class so now when
this controller matter throws any
exception while processing a user's
request spring MVC framework is going to
look for an appropriate exception
handler method in this class if it finds
an appropriate method for that exception
it will simply execute that otherwise
it's going to return the default error
webpage back to the clients browser as a
response so with this new approach you
really don't need to include exception
handler methods in each controller class
separately you can define all of them
globally at one place with the help of
this concept alright now one last
concept before I find out this tutorial
if we observe each method here in this
class what we are doing we are first
locking information of thrown exception
and then returning mu name and this is
what we are doing in this exception
handler method - and in this method also
now spring MVC framework says he
developers if you have to perform just
these two tasks in each exception
handler method then you really don't
need to write such a big Java class in
your application and you can perform all
such handling tasks by writing a very
simple beam definition in your springs
configuration file like this
so this being definition what I have
placed over here is exactly doing the
same thing as what this class is
performing let me explain
so here with this beam definition we are
instructing spring MSE hey spring MVC
finger when any of the controller
classes through a nullpointerexception
choose return this few name exactly like
this exception handler method here and
here
when are you exception is thrown by any
of the control classes just an i/o
exception view name exactly like this
exception handler method and for all
cases when any of the control classes
threw some exception which is not
present in this list just you turn this
default error view exception Union
exactly like this third exception and
the method which we have placed over
here now if you observe via logging
information of thrown exception before
returning you name and that's something
we are doing with the help of this
property in this beam definition with
this we are instructing spring MVC here
spring MVC framework before returning
the customized view page back to the
clients browser just log information of
the toun exception exactly what we are
doing here in each exception handler
method in this class so this beam
definition is just another way of doing
the same thing you know so if you like a
simplicity without writing my Java code
just squared with this being definition
otherwise go add with such a class I
would go add with this class going
forward in this time application so I
would delete off this definition the
screen definition from here all right
guys a big thank you for learning spring
MVC with me if you have any feedback or
comments please provide them below the
video or simply write to me on this
email id for all of your queries please
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I'm going to catch you in the next
tutorial