What makes Spring so popular?

Spring is an open-source, comprehensive framework that simplifies enterprise Java development. Since its introduction by Rod Johnson in 2003, Spring has grown into a versatile platform offering a wide range of features to develop Java applications. From building lightweight Java applications to large-scale enterprise solutions, Spring provides a robust ecosystem for developers with built-in support for dependency injection, aspect-oriented programming, transaction management, and more.

How popular is Spring? Here are some stats -

• According to various developer surveys (like JetBrains’ and Stack Overflow’s), Spring consistently ranks as one of the most popular Java frameworks.
• Spring Boot, an extension of Spring, has seen tremendous adoption, with over 70% of Java developers using it in 2023.
• Spring-related libraries account for a significant percentage of downloads from platforms like Maven Central and GitHub.

source - Maven Repository: Web Frameworks (mvnrepository.com) (opens in a new tab)

What makes spring so popular?

It’s all about the ease of developing production grade enterprise Java apps using Spring.

To understand this better let’s understand — Responsibilities of a developer in a Spring app compared to the standard java app

When developing an application using the Spring Framework, the responsibilities are divided between the developer and the Spring container. In a standard Java application the developer typically handles most tasks manually.

Here's a breakdown:

1. Object Creation and Lifecycle Management

• Standard Java Application:
  • Developer: Responsible for creating instances of classes using new. The developer must manage the lifecycle of these objects.
• Spring Framework:
  • Spring Container: Manages the creation, initialization, configuration, and lifecycle of objects (beans). The container handles the creation of beans, ensuring they are properly initialized before being used and correctly disposed of when no longer needed.
  • Developer: Defines the beans and their configurations, either through annotations (e.g., @Component, @Bean) or XML. The developer can also customize the lifecycle by implementing interfaces like InitializingBean and DisposableBean or using annotations like @PostConstruct and @PreDestroy.

2. Dependency Injection (DI)

• Standard Java Application:
  • Developer: Manually injects dependencies by creating and passing objects to constructors, setters, or methods. The developer must track and manage these dependencies.
• Spring Framework:
  • Spring Container: Automatically handles dependency injection, wiring the necessary dependencies into beans based on configuration or annotations like @Autowired.
  • Developer: Defines the dependencies and how they should be injected, either by annotating fields, constructors, or setters. The developer focuses on defining relationships, not on the actual injection process.

3. Configuration Management

• Standard Java Application:
  • Developer: Manages configuration through hard-coded values, properties files, or environment variables. The developer is responsible for loading and applying these configurations at runtime.
• Spring Framework:
  • Spring Container: Loads and manages configuration properties, profiles, and beans through various means (annotations, XML, properties files, YAML). The container applies the appropriate configuration based on the environment.
  • Developer: Configures the application by defining beans, setting properties, and using annotations like @Value or @PropertySource. The developer specifies what the configuration should be, while the container ensures it is applied.

4. Transaction Management

• Standard Java Application:
  • Developer: Manages transactions explicitly by starting, committing, and rolling them back in code, usually with try-catch-finally blocks.
• Spring Framework:
  • Spring Container: Handles transaction management automatically when annotated with @Transactional. It ensures that transactions are correctly opened, committed, or rolled back as needed.
  • Developer: Declares transaction boundaries using annotations or XML. The container manages the actual transaction lifecycle, reducing boilerplate code.

5. Aspect-Oriented Programming (AOP)

• Standard Java Application:
  • Developer: Manages cross-cutting concerns like logging, security, and transaction management within the business logic, often leading to code scattering and tangling.
• Spring Framework:
  • Spring Container: Implements AOP, allowing the separation of cross-cutting concerns from business logic. The container applies aspects such as logging, security, and transactions declaratively.
  • Developer: Defines aspects using annotations like @Aspect and @Around. The container weaves these aspects into the application at runtime.

6. Resource Management

• Standard Java Application:
  • Developer: Manages resources such as database connections, file handles, and threads, ensuring they are properly closed or released.
• Spring Framework:
  • Spring Container: Manages resources automatically, often through bean lifecycle methods or annotations like @Scheduled for tasks.
  • Developer: Focuses on defining how resources should be managed, while the container takes care of the actual management.

7. Testing and Mocking

• Standard Java Application:
  • Developer: Sets up the test environment manually, including creating mock objects and managing dependencies.
• Spring Framework:
  • Spring Container: Provides support for testing with utilities like @SpringBootTest, @MockBean, and application context management.
  • Developer: Writes tests that focus on the business logic, relying on the container to provide the necessary environment and dependencies.

8. Integration

• Standard Java Application:
  • Developer: Sets up the Integration with various technologies manually.
• Spring Framework:
  • Spring provides out-of-the-box integration support for various technologies (JPA, JMS, REST, SOAP) and connectors (Kafka, RabbitMQ), simplifying the setup process with minimal code.

Summary of Responsibilities

• Standard Java Developer: Manages most aspects of application development, including object creation, dependency management, configuration, transaction handling, resource management, and testing setup. The developer has full control but must handle all these concerns manually.
• Spring Developer: Relies on the Spring container to handle many of these concerns automatically. The developer focuses on defining how the application should behave, while the container manages the underlying mechanics, reducing boilerplate code and potential errors.

The Spring Framework, through its container, abstracts much of the infrastructure-related responsibilities, allowing developers to concentrate more on the application’s business logic. This leads to more efficient development, better separation of concerns, and more maintainable code.