What type of dependency injection involves using immutable objects in the system architecture?

The type of dependency injection that involves using immutable objects is called Constructor Injection.

In this approach, all dependencies are passed to the object through its constructor, and after creation, the object does not change its dependencies. This promotes the creation of immutable objects, which enhances the safety and predictability of the system's behavior.

Example in Java:

public class Service {
    private final Repository repository;

    public Service(Repository repository) {
        this.repository = repository; // dependency passed through constructor and does not change
    }

    public void perform() {
        repository.doSomething();
    }
}

Here, repository is an immutable dependency passed through the constructor.