What is the principle of automatic injection in Spring …
The principle of automatic injection in Spring Boot is achieved based on the dependency injection mechanism of the Spring framework.
In Spring Boot, you can enable automatic dependency injection using annotations. Some common annotations include:
- @Autowired: Automatically inject beans by matching them based on their type.
- @Qualifier: When multiple beans have the same type, you can specify a name to match and inject a specific bean.
- @Resource: Similar to @Autowired, injection is done by matching beans by name.
- @Inject: Similar to @Autowired, but it is an annotation defined in the Java specification.
When starting a Spring Boot application, all Beans will be automatically scanned and loaded, and registered into the Spring container. If automatic injection functionality is needed, Spring Boot will automatically search for and inject the corresponding Bean in the container based on the annotation definition.
The principle of automatic injection mainly involves the following steps:
- Scan components: Spring Boot will scan all classes in the specified package to find classes with annotations.
- Create instances: create corresponding instances based on the scanned classes, and register them in the Spring container.
- Analyze dependency relationships: Spring Boot will analyze the dependencies within the instances and locate the Beans that need to be injected.
- Injection instance: According to the dependency relationship, the corresponding Bean is searched from the container and injected into the instance.
By automating the process of injection, developers can reduce their workload and improve the maintainability and readability of the code. Additionally, Spring Boot’s automatic injection also supports multiple methods, allowing developers to choose the most suitable method for injection as needed.
