Spring > Architecture

Overview

Spring follows a layered architecture, making it flexible and modular. It provides different modules for various functionalities, such as dependency injection, web applications, security, and data access.

Key Layers

Spring is structured into multiple layers:

Layer	Description
Spring Core	Manages dependency injection and bean lifecycle.
Spring Web	Facilitates web applications and REST APIs.
Spring Data	Supports database operations and ORM.
Spring Messaging	Provides integration with messaging systems like JMS and Kafka.
Spring Security	Provides authentication and authorization.
Spring AOP	Handles cross-cutting concerns like logging and security.

Spring Core

• Spring Core is the heart of the Spring Framework.
• It provides key functionalities such as bean management and dependency injection.

1. BeanFactory

• The simplest Spring container that creates and manages beans.
• Uses an XML configuration or Java-based configuration to define beans.

2. ApplicationContext

• An enhanced version of BeanFactory with additional features.
• Supports event handling, internationalization, and AOP.
• Common implementations:
  • ClassPathXmlApplicationContext
  • AnnotationConfigApplicationContext

3. Spring Beans

• The objects that Spring manages in its container.
• Defined using @Component and @Bean annotations.
• Example:

  @Component
  public class MyBean {
      public void show() {
          System.out.println("Hello, Spring Bean!");
      }
  }
  

4. Dependency Injection (DI)

• A way for Spring to provide required dependencies automatically.
• Types:
  • Constructor Injection
  • Field Injection (@Autowired annotation)

5. Spring Expression Language (SpEL)

• Used to retrieve values dynamically within Spring.
• Example:

  @Value("#{systemProperties['user.name']}")
  private String userName;
  

6. Event Handling

• Enables different parts of an application to communicate.
• Example:

  public class MyEvent extends ApplicationEvent {
      public MyEvent(Object source) {
          super(source);
      }
  }
  

7. Resource Management

• Simplifies access to files and resources.
• Example:

  Resource resource = new ClassPathResource("config.properties");
  

Conclusion

Spring’s layered architecture makes it flexible, modular, and easy to use for various application types, from monolithic enterprise systems to cloud-native microservices.

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🔗 Related Topics:

• Spring Introduction
• Spring Modules

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