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Spring Boot is a spring module that provides the Rapid Application Development features for spring framework. It is used in creating the standard alone spring-based application which you can run with little spring configuration.
In this article, you can go through the set of spring boot interview questions most frequently asked in the interview panel. This will help you crack the interview as the topmost industry experts curate these at HKR training.
Let us have a quick review of the spring boot interview questions.
The advantages are.
The features of Spring Boot are.
The dependency management of Spring Boot automatically manages the configurations and dependencies. It is not required to specify a version for any of these dependencies. By upgrading the Spring Boot the dependencies of Spring Boot also upgrades automatically.
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The Spring Boot Starters are the set of convenient dependency management providers which is used in the application for enabling the dependencies. These starters make the easy and rapid deployment. All the available starters will come under the “org.springframework.boot” group. Few of the popular starters are as follows:
There are various approaches to create a Spring Boot project using Maven. These are the few approaches that are followed in creating a Spring Boot application using Maven.
The tomcat server is launched automatically when the spring boot is executed as “Run as Java Application” while developing a web application.
Spring Initializr is a web tool of Spring which helps in creating Spring Boot projects by providing the project details. The creating steps are as follows.
With these steps, you can see the Spring Boot project is created with all required dependencies.
Thymeleaf is a server-side java template engine used for web applications. The main purpose of thymeleaf is to bring natural templates for web applications which integrate well with Spring Framework and HTML5 java web applications. For using thymeleaf the following code must be added in the pom.xml file.
Spring Boot Dev Tools are the set of tools which make the application development easier. When the application runs in the production than this module is disabled automatically, repacking of archives are also excluded by default. The Spring Bot developer tools apply the properties to the specific development environments. Add the following dependency into the pom.xml file for including DevTools.
org.springframework.boot
spring-boot-devtools
Spring Boot provides the actuator to monitor and manage our application. Actuator contains the HTTP endpoints. When the application is pushed to production then by using HTTP endpoints you can choose to manage and monitor your application.
In Spring Boot 2.x, the custom endpoint is created using “@Endpoint” annotation. The Spring Boot also exposes the endpoints using @WebEndpointor, @WebEndpointExtension annotations over HTTP with the help of Spring MVC, Jersey, etc.
Yes, the port of the embedded Tomcat server can be changed by using the application properties file. You have to add the property “server.port” in the application properties file and assign it to any port which you want. After assigning the port number, the Spring Boot automatically loads the application properties file and the required configurations will be applied on the application.
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Apply the below steps to deploy a different server with Spring Boot.
The steps of deploying the WAR file onto a server is dependant on the server which you choose.
Apply the below steps for connecting an external database.
The @GetMapping is a composed annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.GET). The @RequestMapping and @GetMapping annotations both of them will support the consume options which are.
consumes = “text/plain”
consumes = {“text/plain”, “application/*”}
The following are the steps for adding a custom JS code using Spring Boot.
If in case a browser throws an unauthorised error, then disable the security or search for a password in the log file and eventually it will be passed in the request header.
@SpringBootApplication:
@EnableAutoConfiguration:
A non-web application can be created by removing the web dependencies from the classpath along with changing the way Spring Boot creates the application context.
By using the Spring Boot Auto Configuration the spring-boot-starter-data-jpa dependency is automatically added to pom.xml file. As this dependency has a transitive dependency on JPA and Hibernate, whenever spring boot sees Hibernate in the classpath, it auto-configures Hibernate as the default implementation for JPA.
You can use jetty instead of tomcat in spring-boot-starter-web, by removing the existing dependency and including the following:
org.springframework.boot
spring-boot-starter-web
org.springframework.boot
spring-boot-starter-tomcat
org.springframework.boot
spring-boot-starter-jetty
The following are the dependencies required to start up a JPA Application and connecting in-memory database H2 with Spring Boot.
You must refer to the following code for including the dependencies.
org.springframework.boot
spring-boot-starter-web
com.h2database
h2
runtime
org.springframework.boot
spring-boot-starter-data-jpa
As the database entities are exposed directly as REST Services, it is not recommended in real-world applications. The domain model and the consumers are the two main things which are considered while designing the RESTful services. But, none of these parameters are considered while using Spring Data REST. The entities will be exposed directly. The Spring Data REST can be used for the initial evolution of the project.
The @ConditionalOnMissingBean annotation is used for instructing an auto-configuration class to back off when a bean exists. The annotation attributes are.
value: It stores the type of beans to be checked.
name: It stores the name of beans to be checked.
WAR is benefited for a considerable measure from Spring Boot while the embedded containers use only one component of Spring Boot for utilization during the improvements.
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1.Add the following plugin in the pom.xml for deploying the Spring Boot application.
2.With the use of the above plugin, execute its package which generates a JAR file. This JAR contains all the required libraries and dependencies. This also contains an embedded server which can run the application as an ordinary JAR file.
To build a jar file, the packaging element in the pom.xml file must be set to jar as below.
To build a war file, you must mention
By using the “@value” annotation you are able to expose the custom application configuration in Spring Boot but the configuration values are distributed through the application. If this is one way than another way is to use a centralized approach instead of using @value annotation.
With a centralized approach, the configuration component is defined using the “@ConfigurationProperties” as follows:
@Component
@ConfigurationProperties("example")
public class SampleConfiguration {
private int number;
private boolean value;
private String message;
With the above snippet, the configured values of application properties will be as follows.
example.number: 100
example.value: true
example.message: Dynamic Message
JPA is a Data Access Abstraction used in reducing the amount of boilerplate code while Hibernate is an implementation of the Java Persistence API that offers the loose coupling benefits.
@RequestMapping:
@RestController:
Example: Consider there is a method example() which should map with /example URL.
package com.hkrtrainings;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class SampleController {
@RequestMapping("/example")
public String example(){
return"Welcome To HKRTrainings";
Ans. Spring Boot is a Java-based open-source spring module useful for Rapid Application Development (RAD). It helps to develop many stand-alone spring-based apps which we can run with a little configuration. Also, it simplifies the usage of the Spring framework for the development of Java.
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Ans. The Spring Boot Annotations represent metadata that offers data regarding a program. It provides additional data about a program that doesn’t include the part of an application we develop. Moreover, it doesn’t directly impact the operation of the code they explain.
Ans. In Spring Boot, Spring Initailizr is a web tool provided by Spring that helps produce the Spring Boot project structure. It supports us while we start a new project from scratch by resolving issues of framework setting. Thus, there is no need to set up the project structure manually.
Ans. Spring Boot CLI refers to the command-line interface which Spring Boot Framework supports. It enables you to build Spring-based Java apps and also helps to execute and test Spring Boot apps using the command prompt.
Ans. Spring Boot offers multiple properties where the file application.properties helps write the application-based property into that file. Moreover, these property files hold various configurations that require the app to run in a distinct environment. The significant Spring Boot application properties' types include command line properties, YAML files, properties files, and externalized properties.
Ans. Spring Data makes it easier for developers to use different types of databases like relational and non-relational, cloud data services, etc. Thus, it makes data access more accessible and still retains the underlying data.
Ans. In Spring Boot, dependency injection is a design pattern that Spring container uses to insert objects to other dependencies. Also, it helps to eliminate the dependency on the various programs.
Ans. Spring Boot has vital features that Spring doesn’t have. Key features like auto-configuration save much time for developers from drafting long-form codes. It also makes the application development process much more manageable. Further, some other vital features that Spring Boot offers include Starter POM, Actuators, Scanning Components, Version Management, InMemory database, etc.
Ans. Spring Boot uses some relaxed binding rules for binding various Environment Properties to map with the bean property name. It maps with the property name even if there is no exact match. Relaxed binding is highly relevant for the type-safe binding of configuration properties within Spring Boot.
Ans. IOC container is a robust Spring framework useful for applying automatic dependency injection. It helps in managing the creation of objects and their lifetime. Also, it helps to insert dependencies into the class. The IoC container inserts the dependency objects using a constructor, a method, or a property at the runtime and ejects the same at a relevant time.
Ans. The auto-configuration property in Spring Boot specifies the database connection information and connects the database to H2 automatically. It does so because Spring Boot auto-configuration configures all the application dependencies.
Ans. The default H2 database that Spring Boot configures is called “testdb.”
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Ans. Application development has to deal with multiple environments like Dev, QA, Production, etc. Every environment needs a different configuration. So, Profiles help here to separate the various portions of application configuration. Also, they make it handy for different environments. Thus, Spring Boot offers some features using which we can mention the active profiles for a particular environment. Also, we can specify the configuration of multiple environments for different profiles.
Ans. Spring Boot mostly prefers to use the tomcat server, but we can prevent Spring Boot from starting a server automatically. For this, we can avoid including the web server starter within our dependencies.
Ans. To validate or authorize an Actuator in the Spring Boot app, we have to insert the spring-boot-starter-actuator dependency within pom.xml.
Ans. To check all the environment properties in the Spring Boot application, we need to enable the Actuator endpoint “/env.” It returns all the properties that run the Spring Boot app.
Ans. Spring Boot enables developers to execute similar applications in multiple environments. Here, the external configuration supports them to do so. The below sources are the possible ones for external config in Spring Boot.-
Ans. To register a custom auto-configuration class in Spring Boot, we must state the annotation @EnableAutoConfiguration with the key META-INF/Spring.factory file. You can also opt for the annotation @SpringBootApplication to one of the configuration classes.
Ans. The following are the most commonly used Spring Boot CLI Commands.:-
-run, -jar, -install, --init, -shell, -help, -test, -grap, -uninstall, -war, etc.
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Ans. The boundary or border of the Transaction begins from the Service Layer as it defines the transaction boundaries. This layer also holds the logic of business transactions.
Ans. For logging a configuration in Spring Boot, we can use Log4j2 as Spring Boot supports it. Thus, we need to include “Log4j2” for logging a configuration.
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