Complete hiring guide for Spring Boot developers

About Spring Boot

The Java-based Spring Boot is an open-source web framework used for microservice creating and standalone applications. Spring Boot shortens the length of a code and makes the Spring application run easily, while the Spring framework achieves flexibility and infrastructure support through dependency injection.

Spring Boot will automatically configure the Spring application, provides standalone quality without app deployment with web servers, and also is opinionated in terms of determining what packages and defaults need to be installed for dependencies.

Spring Boot developer stats

Presently, there is a high demand for Spring Boot in the enterprise world due to the excellent, high scalability and availability.

Up until now, more than 37.000 commits have been uploaded to GitHub successfully. To clarify, a commit is a snapshot of a repository (central location of data) that displays all the latest source code changes directly to the repository.

Interviewing a Spring Boot developer

Helpful tips for a pre-screening interview

Before a Spring Boot developer is hired, the experts conducting the interview must always prepare several brief questions for finding out if the candidate meets all criteria needed within a company. Essential questions are asked first, and then the next phase is the group of technical and practical questions.

Our talent acquisition specialist Maria Kyryliuk emphasized:

“Developers talking passionately about their job, great soft skills, being respectful during the interview and ensuring camera visibility and functioning, as well as attention to the conversation, good English language proficiency are all great signs. And of course, if I feel there is a good conversation flow and mutual understanding, this is the final impression that rounds up the interview”.

Top technical skills to look for in a Spring Boot developer

A good Spring Boot developer ought to know several sets of technical skills for the execution and completion of assigned tasks.

Regarding architecture and software design, the perfect match should know a few architectural patterns, as such:

• Peer-to-peer pattern
• Broker pattern
• Master-slave pattern
• Model-view-controller pattern
• Layered pattern
• Event-bus pattern
• Client-server pattern
• Blackboard pattern
• Pipe-filter pattern
• Interpreter pattern

Next, is the OOP, or Object-Oriented Programming, and its basic concepts are encapsulation, abstraction, inheritance, polymorphism, user-defined types, predefined types, and operations too.

There is another crucial skill that is a must-have, and that is knowledge of microservices and their usage. The Java developers have to update their skills and knowledge and follow the trend of microservice building, instead of monolithic applications. For this, a good knowledge of Docker Container is a needed prerequisite.

Docker is proven to be useful in not just creating, but compiling microservice applications as well, and in various environments too. In turn, the developers need to know the DURS principles well, and they serve as a Microservice basis. There are a few basic principles of DURS: failure isolation, domain-driven design, decentralization, continuous delivery, and DevOps too.

The experienced Spring Boot developer needs to know the proper usage of microservice architecture areas too. Those key crucial areas are authorization, authentication, network security, data security, and deployment too.

As far as microservice patterns go, the listed ones below are favored and practiced by seasoned developers.

• Delivery pipelines
• GraphQL APIs
• Secure by Design
• Docker Rootless Mode
• HTTPS needs to be used for securing
• Handling Sensitive information
• Dependencies need to be scanned
• Avoiding Security attacks
• RSocket Endpoints
• Time-based Security
• Cloud and Cluster specific Security best practices
• Access and Identity Tokens
• Scan Docker and Kubernetes Configuration

The developer also needs to know about microservice best practices, listed below:

• Microservices targeted to user needs
• Microservices API Design Practices
• DevSecOps approach
• Defense in depth pattern
• Managing Sessions
• Automatic security updates
• Centralized software for security and monitoring
• Aggregating application logs
• Distributed tracing

DevOps Tools

Another major plus for the developer is knowledge and skills about DevOps. Knowledge about one or more tools of the ones listed below is a good asset:

• Docker
• Ansible
• Jenkins
• Raygun
• Phantom
• Nagios
• Puppet
• Gradle

Unit and Mockito

Developers need to create and develop suitable unit tests for the specific code. For Java code unit testing, JUnit is always used. JUnit also has a parent framework, Xunit. Within a project, unit testing coverage is ensured through unit test suites execution and implementation. The Unit Testing is done manually, but also with automated methods as well.

There is a principle called “first testing, then coding”, and JUnit is based on exactly that. Simply put, JUnit assists in creating better efficiency and quality of the developer’s work. The features of this open-source software framework are:

• Annotations
• Assertions
• Test Runners
• Automatic Test suite execution
• Test Suites
• Test progress
• Fixtures

A typical unit test contains a test case for checking the program functionality or a method within the class. With the input and result in mind, the test case is created to check both the input and results. The input precondition checks are complete.

Also, the postcondition result checks are complete. For each test case, you can appoint one single positive and negative test accordingly. Such tests could be integrated with tools like Ant, Maven, and Eclipse, and can be integrated with IDEs too.

What sets apart a great Spring Boot developer from a good one?

The perfect match is a great Spring Boot developer who has a good understanding and great knowledge of Java web standards such as filter and servlet. Another plus is if the developer knows messaging queues (ActiveMQ/RabbitMq/Kafka), docker, microservice patterns, and how a cache server works (Redis). The developer also should be capable to write a clean code and applying TDD practices well.

How Proxify helps you find the best Spring Boot talent

If you take on the hiring and talent matching process yourself, the whole process of matching a talent could become difficult without help. This process can consume a lot of time for successful completion from start to finish since it includes more than just publishing an ad or scheduling interviews with candidates and applicants.

The process will include spending a lot of time, as well as resources for onboarding and even training candidates where it is fit, and more processes along the way. And also, just imagine all the costs and consequences if you choose the wrong candidate during the hiring process and selection.

The Proxify talent acquisition specialists and experts can offer you their specialty through a meticulous and time-saving process of choosing the right talent match for you, because we highlight top-tier developers that can start work almost immediately, in a matter of days upon being selected.

Our process of matching the right talent consists of:

1. Self-assessment tasks that are assigned to the candidates who are shortlisted

2. A pre-screen call that recruiters schedule with candidates that completed an initial task successfully. In this phase, we focus on testing technical, and non-technical skills, proficiency in the English language, and also past and current experience of the candidate.

3. The next step in the process is a precise, technical task through an assessment test

4. Lastly, we finalize the process with a technical interview that is organized and led by a Spring Boot developer with extensive experience.

We give our best efforts and attention, and we ensure that the time needed for hiring a perfect match is shortened, unlike most agencies or recruitment service providers who could stretch out the process for quite some time. This is mainly because the Spring Boot framework skyrockets in popularity for years in a row-most prominently with Proxify, where the demand and need for this have increased significantly in the whole last decade.

Essentials and assessment of a Spring Boot developer

We figured the best people to answer the question of how to find the essential factors that make a Spring Boot developer a good hire, are our own technical interviewers and developers. For this reason, we interviewed Koray Gecici, Besfort Shehu and Ramazan Sakin, and asked them to give us their personal tips on the essentials when assessing the seniority, experience and technical knowledge of Spring Boot developers.

According to Software Engineer and Spring Boot developer Ramazan Sakin, a fit candidate should know of:

“The VCS concept, as well as Git usage, additionally also having experience with CI/CD and tools such as Bamboo, Jenkins, GitLab among others.”

Ramazan Sakin

Further, Software Engineer and Spring Boot developer Besfort Shehu also adds:

“The right fit should know about Starter POMs, Autoconfiguration, Spring Boot CLI, as well as Spring Boot Initializer.”

Besfort Shehu

Computer Engineer and Spring Boot developer Koray Gecici also added:

“For assessing expertise, the focus is on asking what the developer knows about dependency injection, bean instantiation by an IOC container and IOC in general, the meaning of a controller, service, repository and entity packages, autoconfiguration, code coverage, and branch coverage, as well as differentiating between integration tests and unit tests”.

Koray Gecici

Benefits of Spring Boot

Using Spring Boot brings numerous benefits, and confirms the all-encompassing practicality that makes the work process simple and functional for engineers and developers, and from many aspects as well.

One benefit of Spring Boot is the usage and reliance on Java, otherwise, perhaps the most popular programming language, but also, provides a testing setup that is default and intended for Java-based applications.

Another significant benefit is autoconfiguration, and experts unanimously agree on this. It means the Spring application is easily configured in a simple way, and according to the JAR dependencies the developer chose.

What benefits did Spring Boot developers mention?

We asked our developers at Proxify about their experience with Spring Boot and what they found to be the most useful and practical features and benefits in this regard. Relying on their expertise, we collated valuable information below.

Sakin emphasized:

• No need for XML configuration
• Reduced amount of boiler-plate code
• Embedding of Tomcat, Jetty, and Undertow
• Less time is needed for development, through a RAD platform (Rapid Application Development)

Furthermore, Gecici adds:

• Simple, practical, and easy start and setup
• Simplified management of dependencies

And also, Shehu further elaborated with:

• No need for WAR files deployment
• Rich and broad user community and also access to free learning sources and materials
• Creating standalone applications

Additionally, other Spring Boot benefits to mention are:

• Remote access managing/impeccable admin support
• Included plugins for working with databases
• HTTP servers embedding

Spring Boot interview questions and answers

1. Explain the difference between Spring Boot and Spring.

Expected answer: Spring represents an open-source framework which supports Java apps, whereas Spring Boot is a microservice-framework, an extension to Spring that is added over the Spring framework. We can conclude that Spring contains multiple frameworks (or ‘layers’), and Spring Boot is one of them. The latter though has proven easier to work with, and removes the otherwise required boilerplate configurations (when you finalize a Spring app setup).

2. What is the meaning of Spring Boot JPA?

Expected answer: JPA is a short term for Java Persistence API, an interface, and it’s used for relational data management for the Java apps. For working with JPA, we need to include ORM too (Object Relation Mapping)—these two are connected because ORM enables us to get database tables as a result of the conversion of Java objects. Generally, JPA is excellent for small processes in a query and shortens the boilerplate code.

3. What are Spring Boot ‘profiles’?

Expected answer: When there are parts of an app configuration grouped together, we call these profiles. The profiles represent a group of configuration settings, and this grouping helps us to correctly set a precise, accurate configuration in the respective, suitable environment.

4. What can you say about the ‘Initializr’?

Expected answer: If we need to generate a structure of a Spring Boot project, we use the web-based tool called Spring Initializr. This tool helps devs choose the best and most suitable project configuration and helps in using an expandable API the best way possible. We could see the initializer as a catalyst of a sort or generator for the structure of a Spring project.

5. What is ‘thymeleaf’?

Expected answer: The server-side engine, Java-based library that a dev would use for creating web apps is called Thymeleaf. This library helps us to create and process text, CSS, XML, HTML, and JavaScript as well. What makes this library useful and good to work with is that it is quite extensive, it shortens the overall development time, and doesn’t require back end for prototyping templates.

6. What can you say about Spring YAML configuration?

Expected answer: First, we need to define and explain YAML and its correlation to Spring Boot afterward. YAML (Yet Another Markup Language) represents a clearly-readable, flexible language for data-sterilization, and it can even be a suitable replacement for some languages, like for example JSON. One big perk of YAML is that you can map it incredibly easy into native datas. Other perks of YAML are the easy readability, so it’s a perfect asset for configuration work, as well as enabling easy automation of processes. In context with Spring Boot, YAML would be ideal to use it when we work with hierarchy configurations and we need to specify them neatly.

7. What can you elaborate about Spring Boot ‘main class’?

Expected answer: The Spring Boot main class that contains a main method within. This class is most frequently seen in Java apps. In the context of Spring Boot, the main class propels the SpringApplicationContext because the class contains the method public static void main()

If we have several declared main classes in an app, with Spring Boot we can easily pinpoint and define a ‘main class’ within the configuration.

8. Define the IoC container and its context in Spring Boot.

Expected answer: Dependency injection becomes incredibly effective and simplified when it’s automatic, and this sort of automatic process is done with the programming principle IoC container. There is no more manual object management if you use IoC with Spring Boot, and all objects with their dependencies will be perfectly configurated and assembled.

9. What are Spring Boot Devtools?

Expected answer: Firstly, Devtools are a set of tools, or a module that helps the dev to test and debug codes, and overall simplify their work. More precisely in this context, the Spring Boot Devtools are an enhancement released by Spring, and included as part of the Spring Boot 1.3.

These Spring Boot Devtools bring great improvements to working with Spring Boot, like:

• Automatic Restart allows for a simple Java class reload, followed by its server-side configuration too.
• Remote Update and Restart—With this, we can easily restart and update an app remotely, by monitoring all of the file changes in a classpath and immediately sending them to a remote server. In the end, this server is restarted.
• Property Defaults, for easy disabling of caching, and simple page updating without the need to restart the app—all with the help and implementation of Thymeleaf and its ‘spring.thymeleaf.cache’
• Remote Debug Tunneling—Tunneling of JDWP (Java Debug Wire Protocol) directly to the app, through HTTP is incredibly easy now.
• LiveReload is the included server in the Devtools, and it’s enabling the app to start refreshing the browser in an automatic way. This browser-refreshing, or ‘auto-refresh’ would occur with all changes we do along the way.

In summary here, expect the Spring Boot app to restart fast when you make code changes.

10. What is @RequestMapping? And @GetMapping?

Expected answer: The type of annotation that gives us information for the routing is called @RequestMapping and it is used mostly for method-level or class level within the controller class. So, if you use @RequestMapping, expect mapping out of a global request path on the controller class.

Unlike the class-level annotation mentioned above, @GetMapping is the composed annotation that’s connecting methods. This annotation will find all HTTP GET requests and map them easily to certain handler methods as needed.