What methods are used to implement dependency injection into Bean objects?

Dependency Injection in Java Bean objects is usually implemented using the following methods:

1. Constructor Injection — dependencies are passed through constructor parameters. This ensures immutability of dependencies and ease of testing.

2. Setter Injection — dependencies are set via setter methods after object creation. It allows changing dependencies after creation but can lead to an object state with uninitialized dependencies.

3. Field Injection — dependencies are injected directly into class fields using annotations (e.g., @Autowired in Spring). It is convenient but complicates testing and breaks encapsulation.

Example of constructor injection in Spring:

@Component
public class Service {
    private final Repository repository;

    @Autowired
    public Service(Repository repository) {
        this.repository = repository;
    }
}