A Java-based, open-source framework to create web applications, Spring Boot has been dominating the web development landscape ever since the official release of Spring Boot 1.0.0 in April 2014. 

Because of its ability to simplify the process of developing complex applications, the enterprise-grade Spring Boot framework is today among the most widely used Java-based technologies to build scalable and robust web applications.

If you are appearing for a job interview and looking for a set of spring boot interview questions and answers, you have come to the right place. This document includes a collection of spring boot interview questions and answers for experienced and beginners, which will surely help you secure a dream job. Here we go.

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Top Spring Boot Interview Questions and Answers for Beginners

Here are the most frequently asked spring boot interview questions for beginners.

1. What is Spring Boot and what are its Benefits?

Spring Boot represents a fusion of the lightweight Spring application framework, configuration annotations, and embedded HTTP server.

Made available with an auto-configuration feature, and support for Spring Initializer, Groovy, and Java, Spring Boot reduces Integration Test, Development, and Unit Test time.

It aids the development of fast, responsive, and secure web applications, providing users with a complete configuration and programming model for Java enterprise applications.

Spring Boot, utilizing the core features of the Spring application framework, offers a faster development technique for RESTful or REST architecture-based web services. 

2. What makes Spring Boot superior to JAX-RS?

By leveraging Spring Boot features, users can experience significant advantages over JAX-RS, including:

  • Fast deployment
  • High scalability
  • Container compatibility
  • Minimal configuration
  • Lower production time
  • Increased productivity 
  • Reduced development time
  • Easy monitoring and management of applications

3. What Spring Boot features help develop Microservices Applications?

Primarily used for developing microservices-based applications, Spring Boot offers the following key features for configuring, developing, and deploying microservices architecture.

  • Integrates a tool called the Actuator, which enables users to manage and monitor applications
  • Provides support for embedded servers, such as Jetty and Tomcat
  • Users can simply run war files, without deploying it
  • Includes an Auto-Configuration functionality, allowing users to configure Spring applications automatically
  • Supports HTTP client Feign

4. Why Spring Boot is preferred over any other framework?

The Spring cloud that comes with Spring Boot, includes vast libraries, which is one of the major reasons why most developers prefer the Java-based Spring Boot. In addition, Spring Boot offers superior compatibility with Spring frameworks, and it also provides excellent support for docker containerization, heightening performance, and useability. Some of the most compelling reasons for using Spring Boot include: 

  • Provides the best means to configure Java beans
  • Offers robust batch processing 
  • Helps users effectively manage Representational State Transfer (REST) endpoints
  • Integrates an auto-configuration tool, eliminating the need for manual configuration 
  • Enables  annotation-based configurations
  • Ease of dependency management
  • Includes embedded servlet containers

5. What are the key dependencies of Spring Boot?

Mentioned below are important Spring Boot dependencies that need to be added to a Gradle-based or Maven-based application, to ensure application compatibility with Spring Boot features.

  • spring-boot-starter-parent
  • spring-boot-maven-plugin
  • spring-boot-starter-test
  • spring-boot-starter-security
  • spring-boot-starter-actuator
  • Spring-boot-starter-web

Top Spring Boot Interview Questions for Experienced Developers

The spring boot interview questions for experienced developers deal with the concepts in greater depth and are meant to test the working knowledge of the candidates.   

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6. What annotations are used to create an Interceptor?

A prominent functionality of Spring Boot, Interceptor uses the annotated class @Component, and it implements the interface HandlerInterceptor.

The interface contains 3 main methods, which are:

The preHandle() Method − preHandle() is used for intercepting the request prior to the implementation of the handler. If preHandle() returns a “true” boolean value, developers can continue with handler execution. If preHandle() returns a “false” boolean value, developers should stop the handler execution. 

preHandle() implementation looks like:

 @Override

    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {

        logger.info(" Pre handle ");

        if(httpServletRequest.getMethod().equals("GET"))

            return true;

        else

            return false;

    }

The postHandle() Method − postHandle() is used for intercepting a request following the implementation of the handler. It allows the manipulation of the ModelAndView Object before users render it.

postHandle() implementation looks like:

@Override

    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

        logger.info(" Post handle ");

        if(modelAndView.getModelMap().containsKey("status")){

            String status = (String) modelAndView.getModelMap().get("status");

            if(status.equals("SUCCESS!")){

                status = "Authentication " + status;

                modelAndView.getModelMap().put("status",status);

            }

        }

    }

The afterCompletion() Method − A HandlerInterceptor callback approach, the afterCompletion() method is used when the entire request gets completed.

afterCompletion() looks like:

@Override

    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

        logger.info(" After Completion ");

    }

}

7. What is a Swagger in Spring Boot?

Swagger is used for clearly detailing and documenting RESTful APIs in a machine-readable and human-readable format, which is easily comprehensible for testers and developers, as well as individuals having little knowledge of source code.

Enabling hassle-free application discovery, development, and integration, Swagger allows API consumers to interact with remote services with minimum implementation logic.

8. What are Profiles in Spring Boot?

Profiles in the Spring framework enables users to map components and beans to specific profiles, such as the Development (dev) profile, Production (prod) profile, or the Test profile. 

In Spring Boot, the annotation @Profile is used to map components and beans to a certain profile. 

Developers can also set up profiles using the SpringApplication, for instance, SpringApplication.setAdditionalProfiles("dev");

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9. What differentiates Spring Data JPA and Hibernate?

A Java Persistence API (JPA) implementation, Hibernate facilitates Object-Relational Mapping (ORM), allowing users to store, retrieve, map, and update application data to and from Java objects and relational databases. Hibernate maps the data types in Java to SQL (Structured Query Language) data types, and the classes in java to the database tables, relieving developers from scripting data persistence SQL programs. 

A Spring Data sub-project, Spring Data JPA, on the other hand, gives abstraction over the DAL (Data Access Layer) applying JPA and Object–Relational Mapping implementations, such as Hibernate. Spring Data JPA facilitates the smooth implementation of JPA repositories, and it intends to improve the overall implementation of DAL to a great extent. 

10. How are the @RestController and @Controller Annotation different?

The traditional Spring @Controller annotation specifies that an annotated class represents a controller. It’s basically a @Component specialization, and it is autodetected via the classpath scanning. The @Controller annotation is used along with the annotated handler methodologies based on @RequestMapping annotations.

Developers use the @RestController annotation to develop RESTful web services, utilizing the Spring Model–View–Controller (MVC).  The Spring @RestController maps the request data to specified request handler methods. Once the handler method generates the response body, the @RestController modifies it to XML or JSON response.

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When you apply for a web developer job, browse through the spring boot interview questions and answers above to make yourself fully interview-ready. However, if you are looking to upskill, or if you want to learn more about full-stack java development, check out Simplilearn's 100% job-guarantee Full Stack Java Developer course that ensures a starting salary of up to ₹5 lakh per annum.

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