Top 10 Spring Boot Interview Questions with Answers & Examples

What's going guys welcome to this video where  I want to talk to you about the top 10 Spring   Boot interview questions with answers as well as  examples so if you're brand new to the channel   we've got a brand new platform which covers Spring  and Spring Boot Java DevOps and we even have  

a complete road map that you could follow so go  check it out but in this video I want to go over   the top 10 spring interview questions because this  is something that a lot of you have been asking   for so I'm going to be jumping between the slides  as well as um Intelligj so that you can see how  

things work but hopefully by the end of this video  you should have a clear understanding and be ready   for tackling interviews about Spring Boot all  right so let's begin with the very first question   that is what is spring boot and how it differs  from spring framework so this one right here if  

you haven't done much of um Spring Framework then  you kind of need to know about Spring Framework   to be honest and Spring Framework is mainly um  about dependency injection really and before   Spring Boot even existed we had to configure  pretty much everything ourselves by using XML  

and yeah it was nightmare so Spring Boot is an  extension of the Spring framework that simplifies   the application development by autoconfiguring  the application based on the dependencies that   you have so I'll show you this uh when it comes  to auto auto configuration and I'll show you an  

example for this in a second so also it provides  embedded servers such as Jerry Tomcat and I think   undertoe as well and it eliminates the need for  XML so if you've done Spring before it used to   be a nightmare um and uh the cool thing about  Spring Boot is that it provides production ready  

uh features such as health checks and metrics with  Spring Act so in here I have IntelliJ and this is   pretty much a bare uh bone spring application that  doesn't have much but essentially in here you can   see that all I need is this annotation in here  and if I run the application you should see that  

we have you know you've seen this uh time and time  again and if you haven't we've got courses on this   we can see here Tomcat started on port 8080 and  here we have a web server which is up and running   and we can start to implement restful APIs and you  can see the context path is for slash but you see  

that we haven't done anything right so we just  added the dependency and we get all of this out   of the box so this is Spring Boot all right now  this leads nicely into the advantages of using   Spring Boot so essentially faster development  with auto configuration so you've seen that I've  

only added one annotation and then we have a web  server up and running we have Jackson provided so   JSON serialization and D serialization out of  the box and the reduced boiler plate embedded   servers as as I've just said um it also provides  microservices ready architecture so spring boot  

really shines when you want to use microservices  um I've also mentioned about production ready with   actuator and easy dependency management with  spring boot starter dependencies so I'll show   you this in a second so this is pretty much it so  if I actually show you this dependency in here so  

in here if I open up gradal so I'm actually using  gradal this time so build.gradal and in here you   can see that we have dependency section in here so  have a look so we have this dependency or spring   framework and then spring boot starter so spring  boot starter and then web so for writing restful  

APIs we have web for interacting with the database  we have multiple different dependencies so here if   I click on starter for example say that you want  to work with SQL so here maybe spring data JPA   so I can select that um and in here let me just  say okay even though that's not going to work  

but you can see that so this follows the exact  same pattern spring boot starter and then data   jpa so the beauty with this is that we have these  dependencies that autoconfigure a bunch of stuff   for us without without us having to do much so  let me actually undo this because we don't need  

this dependency in here and let me just reload  that all right perfect let's move on to the next   question all right so this next question I've just  showed you actually what is spring boot starter so   essentially is a set of convenient dependencies  descriptors you can include in your application  

so if you want to uh build restful APIs you have  spring boot starter web which bundles spring MVC   Jackson and embedded Tomcat if you want to  work with databases and a bunch of other   things basically you always have a starter for  whatever you're trying to build and it simplifies  

dependency management by grouping commonly  used libraries for specific functionalities   nice and easy all right the next question is  what is spring boot auto configuration so you   see that if you add a dependency you get stuff  out of the box which is given for free right so  

this happens because spring boot uses at enable  auto configuration so this is one annotation and   um it automatically configures beans based on the  class path and property files so as you saw with   um spring boot starter web it's on the class path  it auto configures spring mvc dispatcher serlet  

and Tomcat so if I go back to Intelligj and open  up the sample application in here and you can see   that we have this annotation and uh I'll come back  to this annotation in a second but what I can do   here is I can add parenthesis and then I can say  exclude in here and say that I want to exclude  

just like this and in here I can say or do spring  framework.oot boot dot autoconfigure dot web dot   and then serlet dot and then web mvc and you can  see this class in here so auto configuration so   dot and then class basically and this class in  here is what configures web MVC so if I click  

on it you can see that it contains a lot of stuff  in here and you can see have a look conditional   on property spring.mc and then the name basically  these are properties so if it's there then enable   if not then do x so I'm not going to go through  this class in here but this is how it works so  

if I close that and in here I could just get rid  of this and we don't need that all right okay so   let's move on to the next question which is the  purpose of the at spring boot annotation so if I   go back to IntelligJ again and this annotation  in here basically it's a wrapper on top of at  

enable auto configuration component scan so at  component scan and in here at configuration so   basically instead of you having to define these  three annotations it's basically a a a wrapper   around those three annotations all right so if I  in here so let me just go back and if I comment  

this and say so here let's just say at so at and  then configuration and then at and then component   scan and then at enable auto configuration and  then let's just run this you can see that things   still work and is the exact same thing all right  so this is the meaning of this annotation in  

here so at configuration marks the class as the  source of bean definitions at component scan this   is where to find and initialize those beans so  currently you can basically specify the packages   so here you can see base packages you can specify  um a different package but by default it uses the  

default package and sub packages and then at  enable configuration so this one in here tells   Spring Boot to autoconigure everything based on  what's on the class path so nice and simple all   right so let's get rid of that and then enable  this let's go back to the next question so we  

just spoke about this so how do you create a REST  API using Spring Boot so very simple so here I'm   not going to even show you how to do this but  you basically annotate the controller with at   rest controller annotation in here and then we use  at request mapping for specific mappings so for  

uh a get request you basically use at get mapping  for a post request at post mapping delete mapping   at delete mappings so on and so forth um then what  is spring boot actuator so this one is one of the   uh production ready features that we we spoke  about it allows you to provide health checks so  

for/actuator for/halth so this is useful if you  have your application behind a load balancer so   the load balancer can keep on sending requests to  this endpoint and then see whether it's healthy   or not also metrics so metrics about a bunch  of things so CPU usage memory so on and so  

forth as well as thread dumps environment variable  beans and a bunch more um then we have how do you   handle exceptions so I think I've done a video  on this but basically you could have um uh but   essentially you could handle exceptions throughout  your codebase but the best thing to do is to use  

the at controller advice as well as exceptional  handler where you have a class where you globally   uh handle all of these exceptions so here's an  example so you say add add controller advice so   this is the class and then here you basically  have a method that handles whatever exception  

that you want and then you have full control of  the status codes that goes back to the clients   all right so this is how to do it then we have uh  spring profiles so uh this basically allows you   to define different configurations for different  environments so uh development test and production  

and um you could imagine that for your local  development environment you want to connect to   a database which is running on Docker for example  but when you deploy to AWS you want to connect to   RDS for example so then you could have the exact  same property in here and then just switch between  

these different profiles uh and then finally how  does spring boot support externalize configuration   so there's few ways so one is by using application  properties or YAML so depending on which one your   team uh follows then you can override by using  command line arguments environment variables or  

uh the one which I people people tend to you  know when they learn about microservices they   think oh I need to use config server but you don't  config server all right um this is just an extra   pet that you need to manage basically a server  um and as you go to production I'm saying here  

um you know if you work for a enterprise or  a large company you know you've got thousands   and thousands of microservices then uh there's  better ways of doing this but anyway so this   allows flexible configuration without modify your  code so this is a beauty by following any of these  

steps and this is pretty much it and if you want  to learn more about Spring Boot we have a complete   road map that teaches you everything you need  to know about Spring Spring Boot Java full stack   development and the whole shebang all right so for  now I'll see you on the next one salam allayikum