Spring Dependency Injection and Inversion of Control Container Concepts

Internal

• Spring Framework Concepts

Overview

At the heart of the Spring Framework is the core container, which comes with a configuration model and a dependency injection mechanism. Support for different application architectures, including messaging, transactions and persistence is built in top of the core container.

Inversion of Control Container

Dependency Injection

Spring Dependency Injection Framework

Configuration Model

This section refers to component configuration. Configuration as in external data that is provided to the application in form of properties or environment variables, and that potentially modifies the behavior of the application, is addressed in the "Application Configuration Concepts" section.

Configuration Metadata

XML-based Configuration

Java-based Configuration (@Configuration). Annotation injection is performed before XML injection, thus the XML configuration overrides the annotations for properties wired through both approaches.

Configuration time. Define what that is.

Configuration class.

Component scanning

Autowiring. @Autowired.

Automatic configuration (Spring Boot autoconfiguration).

Application Context

https://docs.spring.io/spring-framework/docs/5.1.0.RELEASE/javadoc-api/org/springframework/context/ApplicationContext.html

The application context provides:

• Bean factory functionality, inherited from ListableBeanFactory.
• Ability to load file resources, inherited from ResourceLoader.
• Ability to publish events to registered listeners, inherited from ApplicationEventPublisher.
• Ability to resolve messages, inherited from MessageSource.
• Inheritance from a parent context.

The application context is created during the bootstrapping phase of a Spring application.

Is the Spring container and application context one and the same thing? Some texts claim so.

Beans

Any non-trivial application consists of many components, each responsible for its own piece of the overall application functionality. These components coordinate with each other. Spring names these these components beans. The Spring container creates and introduces the beans to each other.

Bean name

Bean alias

Collaborator beans

Describe bean initialization process. Who does it?

Stereotypes.

@Bean What is the fundamental difference between @Bean and the rest (@Component, etc.)?

@Component

@Controller

@Service

@Repository