The Spring Framework is one of the most widely used application development frameworks for Java. First released in 2002, Spring has become the de facto standard for building enterprise-ready Java applications.
In this comprehensive guide, we’ll cover the history of Spring, its architecture and key components, reasons to use it, and how to get started. We’ll also provide tips to keep in mind while you hire Java developers to build Spring-based applications.
A Brief History of Spring
Spring was created in 2002 by Rod Johnson as an alternative to the heavyweight and complex Java Enterprise Edition (Java EE) development model. It aimed to simplify Java development by enabling a programming approach based on the Plain Old Java Object (POJO).
Spring provided a fresh alternative by promoting concepts like dependency injection and aspect-oriented programming to implement application components and business logic. This contrasted the boilerplate code laden model of EJBs in Java EE.
The first version of Spring focused on the IoC container and lightweight component wiring. Since then, the framework has grown tremendously to become a one-stop shop for enterprise Java development. It now spans everything from database access, security, REST APIs, microservices, reactive development, and more.
While new technologies like cloud, containers, and serverless have emerged, Spring remains incredibly relevant today. It has evolved to work synergistically with modern architecture styles.
Why Use Spring?
There are several key motivations for using Spring:
Spring eliminates a lot of boilerplate code for common functionality like security, database access, transactions, and web APIs. This simplifies and accelerates development so you can focus on business logic.
Loosely Coupled Code
The dependency injection pattern enabled by Spring promotes loose coupling between application components and services. Components don’t look up dependencies but have them provided by the Spring container. This facilitates easier testing and extensibility.
Spring encourages a layered architecture with clean separation of concerns between data access, services, and presentation layers. Components within layers are decoupled.
Declarative Programming Model
Spring configuration enables a declarative style of programming. You describe application assemblage and behavior through configuration vs procedural code. This raises the level of abstraction.
Spring provides powerful abstractions over tasks like database access, transactions, caching, web APIs, REST services. This hides complexity and standardizes configurations.
Spring has a thriving ecosystem of related projects like Spring Boot, Spring Cloud, and Spring Data. This provides a full-stack solution for end-to-end application development.
The use of dependency injection and POJO programming model makes Spring applications very easy to unit test. Environmental dependencies can be easily mocked and stubbed.
Spring has seen over 15 years of continuous improvement and stabilized into a hardened technology. It enjoys industry-wide adoption with millions of developers.
Key Components of Spring Framework
The Spring Framework comprises several major modules:
The fundamental functionality of the core container is supplied by Spring. It contains the IoC container responsible for instantiating, configuring and assembling beans using dependency injection. The container leverages Aspect-Oriented Programming (AOP) internally to provide services like declarative transaction management across components.
The Web module provides support for developing RESTful web services and web applications. It contains Spring MVC for model-view-controller implementation and Spring WebFlux for reactive web development. Web MVC offers convenience annotations for mapping endpoints like @GetMapping, @PostMapping, etc.
Spring Data provides an abstraction for working with relational and non-relational databases. It offers consistent APIs across JPA, JDBC, MongoDB, Cassandra, etc. This standardized approach avoids vendor lock-in.
Aspect-Oriented Programming allows you to implement common services like logging, transactions, security, caching as modular aspects applied across components. This eliminates repetitive boilerplate code in each class. AOP enables clean separation of cross-cutting concerns.
The testing module provides mocks and test instances of Spring components to support unit testing and integration testing. It helps ensure components are wired properly and minimizes setup code.
There are many more Spring modules like Spring Boot for rapid application bootstrapping, Spring Security for authentication and authorization, Spring Cloud for microservices and more.
Getting Started with Spring
Getting started with Spring is easy. For a web application, you can initialize a project using Spring Boot which handles auto-configuration.
To build a REST API, create a Spring Boot project add the Spring Web dependency. Annotate a controller class with @RestController, expose some endpoints, and you have a functional REST service!
For dependency injection, define beans in a @Configuration class, inject them into other components via @Autowired, and Spring weaves everything together.
There’s so much more Spring can do from here to build a real-world application. But it provides an easy starting point which you can build upon incrementally.
Things to keep in mind while hiring developers
Given its popularity, there is high market demand for developers skilled in Spring and Java. Here are some tips for hiring:
Assess Core Java Skills
Examine mastery of Java itself including object-oriented design, collections, data structures, concurrency, generics, etc. Spring builds on top of core Java.
Review Spring Module Experience
Look for hands-on experience with key Spring modules like the core container, AOP, JDBC data access, Web MVC, Spring Boot, Security. Real-world usage is critical.
Require Code Samples
Ask candidates to submit code snippets or samples illustrating Java and Spring application design skills, proper layering, configurations, etc. Review for best practices.
Discussion Architectural Patterns
Gauge familiarity with architectural styles like microservices, SOA, event-driven architectures. Understand tradeoffs between different designs.
Examine Back End Knowledge
Verify back-end skills including databases, SQL, ORM technologies like JPA/Hibernate. These provide persistence for Spring applications.
Test Automated Testing Expertise
Spring apps require proper automated testing practices. Ensure knowledge of unit, integration, load, and performance testing frameworks and approaches.
Focus on Problem Solving
Assess Spring competency by discussing approaches to real-world problems vs trivial examples. Evaluate ability to ask clarifying questions.
Consider Java EE Experience
While not mandatory, Java EE experience indicates comfort working in enterprise ecosystems and with skills like JMS messaging, EJBs, application servers, etc.
Review DevOps Knowledge
Deploying Spring applications requires DevOps capabilities like CI/CD, infrastructure as code tools, containerization, orchestration, observability.
Assess Passion for Learning
The best developers are continuously expanding their skills. Look for interested in the broader Java/Spring ecosystem including emerging developments like Spring Cloud Function, RSocket, etc.
The Spring Framework provides an amazingly robust set of capabilities for building modern Java applications, from its core DI container to abstractions for data, transactions, security, web development, and more. Adopting Spring enables easier development, loose coupling, predictable configurations, and tremendous productivity gains. With Spring Boot reducing boilerplate, and the thriving ecosystem of related projects, any Java developer can benefit from learning Spring.
When you hire Springboot developers, be sure to thoroughly evaluate both framework-specific experiences as well as underlying competence in core Java and modern architectural styles. This results in well-rounded developers who can create enterprise solutions end-to-end.
The popularity and maturity of Spring means it will remain a critical framework for Java for many more years. Any Java developer working on enterprise applications will gain tremendous advantages by mastering the Spring Framework.