Top 20 Spring Interview Questions and Answers
If you’re interviewing for a job that uses the Java framework Spring, you’ll likely face questions about its utility and related concepts — so you’ll definitely want to prepare ahead of time. Here’s a quick list of some of the most common Spring interview questions and tips on how to answer them.
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1. How would you explain the Spring framework?
Spring is an open-source Java framework you can use to build websites, apps, and cloud-based services. It provides a basis of reusable code to make it easier to create a Java app or website from scratch.
2. When would you choose to use Spring?
Spring is useful when building web applications that are designed to perform a particular function. Instead of having to write the code that makes these functions possible, Spring pre-loads them for easy re-use. Outside of web development, Spring can also be used for testing and data management.
3. What are GET requests in Spring?
A GET request is an HTTP request used to retrieve information from a server.
4. What are POST requests in Spring?
Similar to GET requests, a POST request is an HTTP request used to add information to a server.
5. What are Spring Projects?
Spring Projects are sub-frameworks within Spring that you can use to accomplish various tasks. Some of the most common include:
- Spring Data: Enables access to various databases.
- Spring Cloud: Commonly used to build microservices.
- Spring Shell: Makes it easier to create REST applications.
There are several sub-projects in Spring, including core, web, JDBC, and ORM integration.
6. What is a configuration file?
In Spring, a configuration file is an XML file that describes how the classes created in a Spring project should be configured and where they can be used.
7. What is a REST API?
REST (Representational State Transfer) is a set of standards for computer systems to communicate with each other via the web. A REST API is a set of functions that allows applications to communicate with RESTful web services.
8. How does dependency injection work?
Through dependency injection, you can spend less time writing code and simply describe how objects are created. The inversion of control (IOC) container then fills in the blanks to wire the components so they work properly. Together, these two components act as the foundation for many of the features you can put into the apps you build.
9. What is Spring Boot, and when is it used?
Spring Boot is an extension that you can add to the Spring framework that allows Spring beans and other key parts of the app you build to be autoconfigured, cutting down on the time it takes to develop the app and the overall amount of code you need to write.
10. What are beans, and when are they used?
A Spring bean is a term you can apply to any object that falls under the Spring Inversion of Control controller. Everything from wiring the component to its configuration and management of the bean is done by the IOC container based on the XML code or Java annotations.
11. What are the supported bean scopes?
There are five bean scopes, including singleton, prototype, request, session, and global session. However, request, session, and global session can only be used with Application Context containers. Singleton is used when there’s only one bean per IOC container, while prototype is suitable for multiple instances in the same IOC container.
12. When would you use the persistence API?
You can use the persistence API to update a database efficiently because it eliminates the need to write individual queries.
13. What is the Spring H2 database?
H2 is a Sprint Boot in-memory database that doesn’t persist. It’s mainly used for unit testing.
14. What is Spring Data JPA used for?
You can use Spring Data JPA to help integrate a database into the API you build using Spring. It’s an abstraction layer that makes it possible to cut down on the number of SQL queries you must write into the code yourself.
15. What is a microservice architecture?
A microservice architecture is an application architecture in which the app is designed as a collection of loosely-coupled services that work together. This architecture is more modular, so services are often easier to debug, maintain, test, and update.
16. How do Spring transactions work?
Spring transactions manage the changes that happen within the system. The basic code needed for these changes, such as starting or stopping a transaction, is already provided in Spring Boot. If you choose to use Spring without Spring Boot, you have to activate transaction management by annotating the application class, or transactions won’t track properly.
17. What is Spring DAO?
Spring DAO (data access object) is a built-in support system to make working with data access technologies simpler.
18. What is Spring Security?
Spring Security is a Spring Project that uses Java-based applications’ authentication methods to decrease security vulnerabilities. It helps protect apps from cyber attacks like clickjacking, and it’s easily customized for specific use cases.
19. Explain the Spring MVC framework
Spring Web MVC is the original web-based framework that is by default included in each Spring framework. MVC stands for model view controller, and each of these three — model, view, and controller — represents the three core elements Spring Web MVC uses to design apps. It also sets the protocol for how HTTP requests are handled within the Java apps you create.
20. Explain reactive programming and how it works
Reactive programming is an event-based system designed to work with the modern network by keeping latency low and workload throughput high. By accounting for back pressure flow control, the system stays elastic and better handles the decoupled elements that make up the system components.
Sharpen your Spring skills
Check out the courses below if you need a refresher on Spring before your interview:
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