Advanced
Data Structures Algorithms & System Design(HLD+LLD)
by Logicmojo

⌚ Explain the term ‘Spring Boot’.

It is a Spring module that offers Rapid Application Development to Spring framework. Spring module is used to create an application based on Spring framework which requires to configure few Spring files.

🚀 Features of Spring Boot that make it different

 • Creates stand-alone spring application with minimal configuration needed.
 • It has embedded tomcat, jetty which makes it just code and run the application.
 • Provide production-ready features such as metrics, health checks, and externalized configuration.
 • Absolutely no requirement for XML configuration.

⌚ What are the benefits of using Spring boot? How it is different from the Spring framework?

Spring boot makes it very easy to build microservices. If you are moving to microservices architecture Spring Boot is among the top frameworks which support tons feature to build microservices quickly. Spring boot has huge community support and Spring Cloud having plenty of modules to integrate almost all popular open source tools. Spring Boot makes it very easy to create a standalone application by providing auto configurations. It provides production-ready features like Actuator.

It is easy to learn and require less code to develop the applications.

It is widely used for:
 • Web development (server-side).
 • Software development.
 • Mathematics.
 • System scripting.

⌚ What are the Spring Boot key components?

Below are the four key components of spring-boot:

 • Spring Boot CLI.
 • Spring Boot auto-configuration.
 • Spring Boot starter POMs.
 • Spring Boot Actuators.

⌚ Mention the advantages of Spring Boot

The advantages of Spring Boot are as follows:

 • Provides auto-configuration to load a set of default configuration for a quick start of the application

 • Creates stand-alone applications with a range of non-functional features that are common to large classes of projects

 • It comes with embedded tomcat, servlet containers jetty to avoid the usage of WAR files

 • Spring Boot provides an opinionated view to reduce the developer effort and simplify maven configurations

 • Provides CLI tool to develop and test applications

 • Integrates with Spring Ecosystem like Spring JDBC, Spring ORM, Spring Data, Spring Security easily by avoiding boilerplate code.

 • Consists of a wide range of APIs for monitoring and managing applications in dev and prod.

⌚ Spring vs Spring Boot

⌚ What do you understand about Spring Boot starters?

This is one of the most popular Java Spring Boot interview Questions asked in technical interviews. Spring Boot starters are a set of components that provide dependencies during the development phase. Starters help initiate the application building process by providing a wide variety of dependencies. Starters in Spring Boot are contained in the org. springframework.boot group.

⌚ Which are the different starters that are available in Spring Boot?

This is a common Java Spring Boot interview question asked in technical interviews. The different starters in Spring Boot include:

1. Spring-boot-starter-aop

2. Spring-boot-starter-test

3. Spring-boot-starter-jdbc

4. Spring-boot-data-jpa

5. Spring-boot-starter-web

6. Spring-boot-starter-security

⌚ How does Spring Boot works?

Spring Boot automatically configures your application based on the dependencies you have added to the project by using annotation. The entry point of the spring boot application is the class that contains @SpringBootApplication annotation and the main method. Spring Boot automatically scans all the components included in the project by using @ComponentScan annotation.

⌚ What does the @SpringBootApplication annotation do internally?

The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan with their default attributes. Spring Boot enables the developer to use a single annotation instead of using multiple. But, as we know, Spring provided loosely coupled features that we can use for each annotation as per our project needs.

⌚ What is the purpose of using @ComponentScan in the class files?

Spring Boot application scans all the beans and package declarations when the application initializes. You need to add the @ComponentScan annotation for your class file to scan your components added to your project.

⌚ What is RAD model?

RAD or Rapid Application Development process is an adoption of the waterfall model; it targets developing software in a short period. RAD follow the iterative
SDLC RAD model has the following phases:

1. Business Modeling

2. Data Modeling

3. Process Modeling

4. Application Generation

5. Testing and Turnover

⌚ How does a spring boot application get started?

Just like any other Java program, a Spring Boot application must have a main method. This method serves as an entry point, which invokes the SpringApplication#run method to bootstrap the application.

 @SpringBootApplication  
public class MyApplication { 
   
       public static void main(String[] args) {    
    
             SpringApplication.run(MyApplication.class);        
               // other statements     
       } 
}

⌚ What are the most common Spring Boot CLI commands?

-run, -test, -grap, -jar, -war, -install, -uninstall, --init, -shell, -help.
To check the description, run spring --help from the terminal.

⌚ Explain how to create a Spring Boot application using Maven.

Well, there are various approaches to create a Spring Boot application using maven, but if I have to name a few, then following are the ways to create a Spring Boot project/application using maven:

1. Spring Boot CLI

2. Spring Starter Project Wizard

3. Spring Initializr

4. Spring Maven Project

⌚ What Are the Basic Annotations that Spring Boot Offers?

The primary annotations that Spring Boot offers reside in its org.springframework.boot.autoconfigure and its sub-packages. Here are a couple of basic ones:
@EnableAutoConfiguration – to make Spring Boot look for auto-configuration beans on its classpath and automatically apply them.
@SpringBootApplication – used to denote the main class of a Boot Application.
This annotation combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations with their default attributes.

⌚ What is the default port of tomcat in spring boot?

The default port of the tomcat server-id 8080. It can be changed by adding sever.port properties in the application.property file.

⌚ Describe the flow of HTTPS requests through the Spring Boot application?

On a high-level spring boot application follow the MVC pattern which is depicted in the below flow diagram.

⌚ What is the use of Spring Initializr?

Spring Initializr is a tool used to create projects in Spring Boot by specifying the project details. The following steps need to be followed to create a project using Spring Initializr:

1. Choose the project and its dependencies, such as artifacts and Groups.

2. Generate the project and extract it into the system.

3. Ensure the source project has the pom.xml file while importing the project and running it.

⌚ What function would you use to enable HTTP/2 support in Spring?

You can enable HTTP/2 support in Spring using the function: server.http2.enabled=true

⌚ What are embedded containers support by Spring

Spring Boot support the main three embedded containers:
1) Tomcat
2) Jetty
3) Undertow.
By default, it uses Tomcat as an embedded container.

⌚ Explain Spring Actuator and its advantages.

Spring Actuator is a cool feature of Spring Boot with the help of which you can see what is happening inside a running application. So, whenever you want to debug your application, and need to analyze the logs you need to understand what is happening in the application right?
In such a scenario, the Spring Actuator provides easy access to features such as identifying beans, CPU usage, etc. The Spring Actuator provides a very easy way to access the production-ready REST points and fetch all kinds of information from the web. These points are secured using Spring Security’s content negotiation strategy.

⌚ How to enable Actuator in Spring boot application?

To enable the spring actuator feature, we need to add the dependency of “spring-boot-starter-actuator” in pom.xml.

<dependency>
<groupId> org.springframework.boot</groupId>
<artifactId> spring-boot-starter-actuator </artifactId>
</dependency>

⌚ How to enable debugging log in the spring boot application?

Debugging logs can be enabled in three ways -

1. We can start the application with --debug switch.

2. We can set the logging.level.root=debug property in application.property file.

3. We can set the logging level of the root logger to debug in the supplied logging configuration file.

⌚ How to Deploy Spring Boot Web Applications as Jar and War Files?

Traditionally, we package a web application as a WAR file and then deploy it into an external server. Doing this allows us to arrange multiple applications on the same server. When CPU and memory were scarce, this was a great way to save resources. But things have changed.
Computer hardware is fairly cheap now, and the attention has turned to server configuration. A small mistake in configuring the server during deployment may lead to catastrophic consequences.

To include this plugin, just add a plugin element to pom.xml:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
</plugin>

⌚ What Does It Mean That Spring Boot Supports Relaxed Binding?

Relaxed binding in Spring Boot is applicable to the type-safe binding of configuration properties. With relaxed binding, the key of a property doesn't need to be an exact match of a property name. Such an environment property can be written in camelCase, kebab-case, snake_case, or in uppercase with words separated by underscores.

For example, if a property in a bean class with the @ConfigurationProperties annotation is named myProp, it can be bound to any of these environment properties: myProp, my-prop, my_prop, or MY_PROP.

⌚ What Is Spring Boot DevTools Used For?

Spring Boot Developer Tools, or DevTools, is a set of tools making the development process easier. To include these development-time features, we just need to add a dependency to the pom.xml file:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-devtools</artifactId>
</dependency>

The spring-boot-devtools module is automatically disabled if the application runs in production. The repackaging of archives also excludes this module by default. So, it won't bring any overhead to our final product.

By default, DevTools applies properties suitable to a development environment. These properties disable template caching, enable debug logging for the web group, and so on. As a result, we have this sensible development-time configuration without setting any properties. Applications using DevTools restart whenever a file on the classpath changes. This is a very helpful feature in development, as it gives quick feedback for modifications. By default, static resources, including view templates, don't set off a restart. Instead, a resource change triggers a browser refresh. Notice this can only happen if the LiveReload extension is installed in the browser to interact with the embedded LiveReload server that DevTools contains.

⌚ What is Spring Boot dependency management?

Spring Boot dependency management is basically used to manage dependencies and configuration automatically without you specifying the version for any of that dependencies.

⌚ Explain different phases of RAD model.

This is a frequently asked job interview. Various phases of RAD mode are:

1. Business Modeling: Based on the flow of information and distribution between various business channels, the product is designed.

2. Data Modeling : The information collected from business modeling is refined into a set of data objects that are significant for the business.

3. Application Generation: Automated tools are used for the construction of the software, to convert process and data models into prototypes.

⌚ What are the commands to run and stop Spring Boot executable jar file?

You need to open cmd or shell window command and use
java -jar
example: $ java -jar myproject-0.0.1-SNAPSHOT.jar

⌚ Mention the differences between JPA and Hibernate.

⌚ What is dependency Injection?

The process of injecting dependent bean objects into target bean objects is called dependency injection.

1. Setter Injection: The IOC container will inject the dependent bean object into the target bean object by calling the setter method.

2. Constructor Injection: The IOC container will inject the dependent bean object into the target bean object by calling the target bean constructor.

3. Field Injection: The IOC container will inject the dependent bean object into the target bean object by Reflection API.

⌚ How do you Add, Filter to an application?

There are three methods to add filter to Spring Boot application:

1. 1. By implementing Filter interface.

2. 2. Using FilterRegistrationBean.

3. 3. Using MVC controller.

⌚ What is Thymeleaf?

Thymeleaf is a Java templating engine commonly used to generate HTML views on web pages apps. However, it is a general-purpose templating engine meaning you can use it outside of web apps.

⌚ What do you understand by Spring Boot supports relaxed binding?

Relaxed binding, is a way in which, the property name does not need to match the key of the environment property. In Spring Boot, relaxed binding is applicable to the type-safe binding of the configuration properties. For example, if a property in a bean class with the @ConfigurationPropertie annotation is used sampleProp, then it can be bounded to any of the following environment properties:

1. sampleProp

2. sample-Prop

3. sample_Prop

4. SAMPLE_PROP

⌚ What do you understand about Spring Data?

This is one of the most popular Java Spring Boot interview questions asked in software engineering interviews. Spring Data is a SpringSource Project that allows developers to easily access cloud-based services, data access technologies, relational and non-relational databases in the Spring framework.

⌚ How can you configure logging in Spring boot application?

Spring Boot comes with support for Java Util Logging, Log4J2 and Logback and it will be pre-configured as Console output. Hence,You can simply specify logging.level in application.properties.

It will set Spring framework logs to debug level. Let’s say you want to put logs to the file.You can specify logger.file in application.properties.

If you want to do logging configuration explicitly, You can also create logback.xml in main/java/resources folder and specify logging configuration in the file. Spring Boot will pick this file and configure logging accordingly.

⌚ Mention the possible sources of external configuration.

There is no doubt in the fact that Spring Boot allows the developers to run the same application in different environments. Well, this is done with the support it provides for external configuration. It uses environment variables, properties files, command-line arguments, YAML files, and system properties to mention the required configuration properties. Also, the @value annotation is used to gain access to the properties. So, the most possible sources of external configuration are as follows:

Application Properties – By default, Spring Boot searches for the application properties file or its YAML file in the current directory, classpath root or config directory to load the properties.

Command-line properties – Spring Boot provides command-line arguments and converts these arguments to properties. Then it adds them to the set of environment properties.

Profile-specific properties – These properties are loaded from the application-{profile}.properties file or its YAML file. This file resides in the same location as that of the non-specific property files and the{profile} placeholder refers to an active profile.

🚀Conclusion

We have now reached the end of this page. With the knowledge from this page, you should be able to create your own programmes with some research, and it's in fact recommended to hone your programming skills with small projects. There is no way to cover all the information you need to be a successful programmer in one course. In fact, programming is a constant learning process, regardless of whether you are a seasoned professional developer or a newbie.

TEST YOUR KNOWLEDGE!