Junior — Middle

What methods are used to implement dependency injection in code?

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Answer from AI

Dependency Injection (DI) in Java can be implemented in several ways:

Through constructor — dependencies are passed to the class constructor.

public class Service {
    private final Repository repo;

    public Service(Repository repo) {
        this.repo = repo;
    }
}

Through setters (Setter Injection) — dependencies are set via setter methods.

public class Service {
    private Repository repo;

    public void setRepository(Repository repo) {
        this.repo = repo;
    }
}

Through interfaces (Interface Injection) — the class implements an interface that allows injecting dependencies.
Using DI frameworks — such as Spring Framework, Guice, which automatically manage creation and injection of dependencies via annotations (@Autowired, @Inject) and configuration.

Example with Spring:

@Service
public class Service {
    private final Repository repo;

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

Thus, DI allows separating dependency creation from their usage, improving testability and modularity of the code.

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