Spring-Boot-201

Question 1

Do we require a parent tag in mvn while configuring the Boot ?

Answer 1

Yes with Mvn a tag is required

Question 2

To which package all the boot dependncies fall on?

Answer 2

spring-boot-starters

Question 3

How the Main class should be?

Answer 3

It should have annotated with @SpringBootApplication

Also provide the arg to SpringBootApplication.run in main method

Question 4

What is mvnw

Answer 4

Maven wrapper, it is an automated building tool by spring boot

Question 5

What goes in tag on pom.xml?

Answer 5

org.springframework.boot>

spring-boot-starter-parent>

Question 6

What is a 12 factor app?

Answer 6

I. Codebase
One codebase tracked in revision control, many deploys
II. Dependencies
Explicitly declare and isolate dependencies
III. Config
Store config in the environment
IV. Backing services
Treat backing services as attached resources
V. Build, release, run
Strictly separate build and run stages
VI. Processes
Execute the app as one or more stateless processes
VII. Port binding
Export services via port binding
VIII. Concurrency
Scale out via the process model
IX. Disposability
Maximize robustness with fast startup and graceful shutdown
X. Dev/prod parity
Keep development, staging, and production as similar as possible
XI. Logs
Treat logs as event streams
XII. Admin processes
Run admin/management tasks as one-off processes

Question 7

Can we have a yml prop also ?

Answer 7

Yes we can have yml also as prop

Question 8

What is @SpringBootApplication composed of ?

Answer 8

@Confuguration, @ComponentScan, @EnableWebConfiguration

Question 9

What does SprinBootaPPLICATION.RUN DOES

Answer 9

It gets to know which class is booting up

Question 10

What is SpringApplicatioBuilder class?

Answer 10

Sometimes you require heirarchy or need multiple things to while booting up , this will help

new SpringApplicationBuilder(Main.cllass).child(otherconfig.class).run(args)

generally the weconfig goes to child part (like these)

Question 11

How you can mute the logging info

Answer 11

new SpringApplicationBuilder(Main.class).logStraytupInfo(false).run(args);

Question 12

How we can have profiles

Answer 12

With the same SpringApplicationBuilder use .profiles

Question 13

How can we add listeners

Answer 13

Yes .listener and then impl the Interface like ApplicationEvent

Question 14

How can we deliberately stop spring assuming the AutoConfiguration?

Answer 14

There are .operators like to SBApp class like :
.web(WebApplicationType.NONE)

Question 15

What @Order will do ?

Answer 15

If you want to execute the Main in certain order

Question 16

How can we provide the prop files to Main

Answer 16

We can use Or @PropertySource, use default application.prop or applicaion.yml and place it in classpath
Yes Env variable can be used also

Question 17

How can the property be accessed in a class?

Answer 17

@Value(“${prop}”)

Question 18

How can be give the prop form cmd?

Answer 18

–prop=val Or -DProp=val

Question 19

How to use mvnw

Answer 19

mvnw spring-boot:run -Dspring.config.name=val

Question 20

What all is included in Spring web

Answer 20

Spring -web, webmvc, webflux & websocket

Question 21

What are the names of he folder for static contents

Answer 21

/static, /public, /resources, /META-INF/resources

Question 22

Can index.html server automatically?

Answer 22

Yes many of the java frameworks does that

Question 23

What flexibility do we have with JSOn and XMl in Boot?

Answer 23

Yes the JSOn HttpMessageConverter is autoadded, and if the App has JSOnXMLExtension in CPath then XML converter will be auto added

Question 24

Can we have more control about JSON to and fro processing?

Answer 24

Yes need to extend JsonSerializer Or JsonDesiriallizer and @JSonComponent.

By default Jackson is provided by Boot

Question 25

Can we change the Jacksoon default date format?

Answer 25

Yes spring.jackson.date-format=SimpleDateFormat

Question 26

Does Boot do the content negotiation by default?

Answer 26

Yes

Question 27

What is the default error page locatin ?

Answer 27

/error

Question 28

Where custom error page be created?

Answer 28

/src/main/resources/public/error : such as 55.html, 404.html, and the like

Question 29

Whic anntoations to be used for handling errors?

Answer 29

@ControllerAdvice & @ExceptionHandler

Question 30

How can custom error pages be registered?

Answer 30

By implementing ErrorPageRegistrar and declaring as Spring Bean

Question 31

Say something about @RestController?

Answer 31

The @RestController offers @Controller also , and it used for handling request mappings, request input or exception handling

Question 32

Say something about @RequestMapping ?

Answer 32

It is used for mapping the Http Methods , request params, headers and mediatypes. It can be used at class or method level

Question 33

Explain @Autowired ?

Answer 33

The autowired can be ommitted , spring 5 and above auto does it, also it is used for injecting the constrtr dependency

Question 34

Explain @PathVariable?

Answer 34

It is used for defining the variable which are coming into path , as /api/{id}, the name should match with the arg type

Question 35

@RequestBody?

Answer 35

This is used to map JSON or XMl data to a Model class.

The Boot auto does it as it auto uses MappingJackson2HttpMessageConverter

Question 36

ResponseEntity?

Answer 36

This return a full details API response with headers and the body which is converted to HttpMessageConvertors and wriiten to HTTP

Question 37

@ResponseStatus?

Answer 37

This is used generally when null is returned with a status code.

Question 38

State some of Principles of Spring FW?

Answer 38

Single Resposibility Principle(SIP)
Open Closed 
Liskov-Substituion
Interface Segregation
Dependency Inversion

Question 39

Explain SIP?

Answer 39

The SIP states that a module, class or fnction must have one resposibility & only one reason to change.

Question 40

If we do not follow SIP, what will be the impact?

Answer 40

The classes will have cyclomatic complexity & poor testability

Question 41

Explain OCP?

Answer 41

It states that class must be open for extension but closed for modification

Question 42

In Boot, how does the Context Component Scan does automatically?

Answer 42

the package of @SpringBootApplication is taken into consideration by default