Spring Boot Interview Questions

Introduction

Spring Boot is a highly regarded framework for developing Java-based applications. This framework has grown in popularity in recent years, with many businesses and organizations using it as their preferred choice when it comes to developing apps. This popularity is partially due to the framework’s capacity to simplify the development process as well as the fact that it offers a stable and scalable platform for creating and delivering applications.

Whether you are an experienced developer or just starting out, this article will provide valuable insights into the key concepts and features related to Spring Boot and help you to demonstrate your understanding of the framework to potential employers.

What is Spring Boot?

Spring Boot is a Java-based framework that follows an opinionated default configuration and enables programmers to create "production-ready" apps quickly and easily. It is based on the Spring framework and offers a simpler approach to developing standalone, production-quality Spring-based apps. It is also well-supported by a large community of developers and provides integration with a variety of popular technologies and libraries, making it a flexible and versatile solution for a wide range of application development needs.

Spring Boot provides default configurations and conventions that can be easily overridden, as well as pre-packaged solutions for common tasks, such as embedded web servers, security, and data access. With Spring Boot, developers can launch their projects quickly and worry less about difficult setup and configuration processes. It is therefore perfect for creating small to medium-sized apps and for quickly prototyping new concepts.

What Are Some of Spring Boot’s Features?

Spring Boot has a lot of important features, such as the Spring actuator, the Spring initializer, the Spring CLI, and auto-configuration. Some other key features of this framework can be seen in the diagram below:

What Gives Spring Boot Advantage Over Other Frameworks?

Spring Boot is preferred over other frameworks due to its simplicity, ease of use, and flexibility. It provides a wide range of features out-of-the-box, such as auto-configuration, embedded servers, health checks, and security features, which help developers get started quickly and reduces the time required to develop and deploy applications. Additionally, Spring Boot has a large and active community of developers who provide support and resources, making it easier to find answers to questions and solutions to problems. Furthermore, Spring Boot is highly adaptable and can be used with a broad variety of application types and architectures, ranging from basic web apps to large microservices.

What Is the Difference Between Spring and Spring Boot?

Both Spring and Spring Boot are frameworks for developing Java applications, however, they have significant differences. Spring provides a comprehensive set of tools and features for developing all sorts of applications, including web apps, mobile apps, and workplace apps. However, using the Spring framework requires a significant amount of manual configuration and setup. Spring Boot, on the other hand, is a framework built on top of the Spring framework_, and as we’ve already mentioned, it simplifies and streamlines the development and deployment of the applications.

Some of the most significant distinctions between these two frameworks can be seen in the table below:

What Exactly Is the Starter Dependency?

The Spring Boot module's starter dependency is a set of pre-configured dependencies that give a quick and easy way to get started with a new project. The starters are classified according to the type of project you're working on, such as a web project, a data project, or a security project. By adding the relevant startup dependency to your project, the developer will get a pre-configured set of dependencies that are ready to use, minimizing the time and effort necessary to set up a new project.

How Many Layers Does Spring Boot Have?

Spring Boot consists of four layers, and they are as follows:

• Presentation Layer: this is the top layer and it is responsible for handling user interactions and presenting data to the user. This layer typically includes components such as controllers, views, and templates. Along with handling HTTP requests, it also manages authentication and JSON conversions.
• Business Layer: this layer in a Spring Boot application is responsible for implementing the application's core business logic and taking care of validation and authorization. This layer typically includes components such as services, repositories, and domain objects.
• Persistence Layer: this layer is responsible for storing and retrieving data from a data store, such as a database, and it typically includes components such as data sources, entity classes, and repositories.
• Database Layer: it is the last layer in a Spring Boot application and it includes all databases such as MySql, MongoDB, and others. This database layer is in charge of carrying out CRUD operations and may contain several databases.

What Is the Flow Architecture of Spring Boot?

The flow of a typical Spring Boot architecture can be seen in the diagram below:

Let us now try and understand the diagram:

1. HTTP requests (PUT or GET) are made by the client.
2. The request is sent to the controller, who maps and handles it. The service logic is then called.
3. All business logic is performed at the service layer. It executes logic on the data that has been mapped to JPA using model classes.
4. If no errors occurred, a JSP page is returned to the user.

What Is a Spring Boot Actuator?

The Spring Boot Actuator is an effective tool for monitoring and managing a Spring Boot application and it provides a number of endpoints for that purpose, including health checks, metrics, configuration data, and trace data.

The Actuator endpoints offer a wide range of information on the functionality, configuration, and state of the application and may be accessed by HTTP or JMX. Utilizing this data will allow you to keep an eye on the program, identify problems, and decide how best to optimize and enhance it. This tool offers a variety of additional capabilities in addition to the usual endpoints, like auditing, caching, and security. These features make it easy to build a secure, scalable, and highly available application with Spring Boot.

How Can You Change the Port Number?

The default port number for starting your Spring Boot application is 8080. If you’d like to change the port number, the easiest and quickest way is to override the value of the default properties by changing the server.port property inside of the application.properties file and restart your application.

One Pager Cheat Sheet

• Spring Boot is a Java-based framework that provides an opinionated default configuration and pre-packaged solutions to quickly create "production-ready" apps and prototype new concepts.
• Spring Boot provides a default configuration for creating customized and adapted applications of various types, including non-web applications, with an embedded web server available for web applications if required.
• Spring Boot has many important features, such as The Spring actuator, The Spring initializer, The Spring CLI, and auto-configuration, which can be seen in the diagram above.
• Spring Boot is preferred for its auto-configuration, embedded servers, health checks, and security features, as well as its simplicity, ease of use, flexibility, and large active community that helps with problems and enables it to be used in a variety of applications.
• Spring provides comprehensive tools for developing applications, but requires a lot of manual configuration, whereas Spring Boot is a framework built on top of Spring that simplifies and streamlines the process, eliminating the need for manual setup.
• Spring is an ideal choice for large-scale projects due to its comprehensive tool set and extensive configuration options, allowing for greater flexibility and control of the development environment.
• The Spring Boot starter dependency provides developers with a quick and easy way to get started on a new project, by adding pre-configured dependencies classified according to the type of project.
• Spring Boot consists of a Presentation Layer, Business Layer, Persistence Layer and Database Layer, responsible for handling user interactions, implementing business logic and carrying out CRUD operations.
• HTTP requests are mapped to the controller, where service logic is called, data is mapped to JPA and, if no errors occur, a JSP page is returned to the user.
• The Spring Boot Actuator provides a variety of endpoints that allow you to monitor and manage your Spring Boot application, allowing you to view information about its functionality, configuration, and state, as well as utilize additional features for auditing, caching, and security.
• Yes, the Spring Boot Actuator offers a variety of HTTP endpoints, health checks, metrics and JMX, allowing for extensive observation and control of a Spring Boot application.
• You can override the default port number (server.port) in the application.properties file to change the port for your Spring Boot application.