Spring MVC Tutorials 43 - Web Services 13 ( Using ResponseEntity with a REST API Controller 01 ) Video Lecture | MVC Tutorials: Web Programming Course - Web Development

guys my name is incacha Cara and I
welcome you to con two cities in some of
the previous tutorials we tried learning
how to develop a REST API which demands
grinds to make put kind of request on it
in other words we learnt how to develop
this REST API controller method and this
quest API controller method seems
absolutely perfect there is no issue
with this when a client is going to make
a put request on this REST API with the
desired information with which it wants
to update John's record it's going to
receive two as response body so how it
has to see the true eyes response body
well the whole idea is whatever this
REST API controller method is returning
this application simply puts that return
value as a response body and friends are
saved to the client in the response
method and that's what we can observe
over here too as response body now an
interesting point which you should go
down over here is this application not
just only sends the response body in the
response method but along with the
response body it sends two more
important information to the flight
response headers you know a bunch of key
value pairs as well as response status
code so indeed a response message
application sends response body response
headers as well as response status code
because in this tutorial I am going to
only concentrate on status code as well
as response body so you can ignore this
tab fully for now so question is what
this status code is all about because
whatever status code an application
sends in the response that informs
client about what has happened
while processing its request at the
server was that request successfully
processed by the application or while
processing that request application
somewhere failed in between so whatever
has happened with that request while
processing it at the server side that's
what an application describes by sending
an aggregate status code to the grind so
different status codes value can be a
different information to decline here
I've listed some of the important status
codes what an application might send to
the client in different circumstances
along with their meaning so when an
application sends status course value as
200 okay to the client it just indicates
claim that the request what it made to
the server was successfully processed
there so here for this sequence I've
received status codes value as 200 okay
it's simply indicating me that the
whatever request I made that was
successfully processed at the
application so the application has
definitely updated John's record with
this information and how I'm so sure
about this by looking at the status code
value this is what 200 okay scan main to
me now if here I would have got some
other status code then I would've
understood something else you know so
depending upon status could a client me
understand what actually has happened
you know at the server while processing
its request now after knowing everything
about status code a question may arise
in your minds in this response message
we are getting response body and we are
getting status code and both of these
are conveying same kind of information
to me it's not that after looking at
status code I would be looking at in
response body or after looking at
response body I would be looking at say
this code because both are conveying the
same kind of information nothing special
here when I say - I would understand
that this must have been successful
processed at the server when I see a
solid force I would understand that it
must be failed somewhere at the server
and saying is what the status code is
conveying to me so why to send two
things in the response message we just
can make same Commission to the client
so you can send either of these two
right you can send either response body
with such kind of information or status
code with you know an appropriate value
and here
what important point you need to
understand is in general developers
around the globe prefer sending status
code for good kind of rest api is then
sending response body so what they
prefer is they do not send response body
with such a kind of you know message
inside it they profess any an
appropriate status code which best
describes the situation so here if we go
with the you know the generally what
developers follow around the globe we
would also not return anything from this
where steep a controller method has
response body so now here this is not
setting as part of a spawns buddy so now
when I am going to make a request of not
get anything as response body and I
don't here for the same as well because
whatever information I wanted to know
you know related to my request all that
information is conveyed to me by this
status codes value which application is
sending to me so it's perfect now so now
when you have decided that you are going
to only send an appropriate status code
you know and you are not going to send
the response body then another problem
arises let me talk about that problem
the problem is but you make a request
and the request has been processed by
this REST API controller method and
let's say while processing it
it doesn't throw any other and it
reaches to the end of this controller
method and it comes out of this
controller method so in all such cases
where rest API controller method process
the request without throwing any
exception in between and reaches to them
and come out of the controller method
application assumes that everything has
gone right while processing that request
within the REST API controller method
and in all such cases it returns 200 ok
as status code which sometimes you do
not want to happen let me talk about an
important case where you don't want
application to sent 200 ok let's say you
make a request and here for this request
this statement is not able to find out
john scott into the database now in this
case what it's going to do well nothing
special it's not going to update jon
secada with this information why because
it hasn't found John's according to the
database so in this case it's going to
happily come till the end of this
controller method without throwing any
exception and there is going to come out
of this controller method and here also
application is going to send 200 ok and
that's something really wrong for such a
case when application hasn't found
John's according to the database it
should not send 200 ok as status code
value it should send some other
appropriate status code which best
describes the situation and this
situation can be best described by
sending the status code values 4.4 not
formed well for not for not for status
code if a client sees then by looking at
it it can very clearly understand that
uh whatever students record it wanted to
update with this information but that
record is not available at the server so
sending an appropriate status code is
very important but point is
if this is not going to throw any
exception application is going to by
default send 200 okay for all cases so
how you can send an appropriate status
code from within this REST API
controller method depending upon
whatever logic you have written inside
it
that's what is the question and the
answer is by making use of something
called as response entity or you can
type all you need to do is you here
specify response entity and return
object of response entity and inside it
just specify what status code you want
to send so here let's say we want to
send status code value as 200 okay so
this is what I have to pass to it
so now when I'm going to make a request
it's going to send me status code as 200
okay all because of this value what I
pass to it now here if I have to
describe status code for the situation
when it's not going to find John's
recording to the database well here all
I need to do is to change it to not
found that's it so in this case this
rest API controller method is going to
send status codes value as for not for
not found C so the whole idea is from
within this REST API controller method
depending upon whatever logic you have
written you can actually choose an
appropriate cell your status code and
send the same to decline here just to
keep this tutorial a bit simpler I am
creating this response entity object in
the end you know at this statement while
I'm returning you know from this
controller method but in your actual
project you got to write here many
if-elsif kind of you know statements and
in what
if else--if or else block you are you
know you are currently executing the
code you just got to prepare response
enter the object you know in that block
with an appropriator status code and
send the same you know back to the
client from this controller method
alright now one last important thing
gets what if for any specific project
requirement in real time scenario you
decide to send this one's body as well
you know in addition to status code then
how to achieve that using this once
entity will that get with you very
easily let's say you want to send here
true value as a spawn spotty in addition
to this status code let's say here you
are sending status code as okay and
along with it you want to send true
value as response body or this is the
way to do that the whole idea is when
you pass only one argument to response
entity object then that argument is
considered as response status to be sent
to the client and when you pass two
arguments to response entity object in
that case a sponsor entity is going to
consider first argument as response body
and second alternate as response status
now another important point which you
have to know down over here whatever
type of response body you are specifying
here you are passing here as an argument
to response entity object it's type you
have to specify over here so here we are
passing boolean values so here we are we
have to specify boolean so the concept
is whatever type of for response body we
are passing here as first alternate you
know same type you have to specify here
so now after this chain and I'm going to
make a request I would get response body
as well as status know whatever have
specified here
because in this table we tried learning
how to send response body as well as
status code from within the USDA
controller method in the next tutorial I
will talk about how to send HTTP
response headers along with response
body as well as response status to the
client all right there's a big thank you
for learning rest IPE concepts using
spring MVC framework we think if you
have any feedback or any constructive
comment please provide them below the
video or simply write to me on this
email id for all of your queries they
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series and I'm going to catch you in the
next part of this tutorial