What ways can dependency injection be implemented besides using constructors?

In addition to constructor-based dependency injection, the following methods can be used:

• Setter Injection: dependencies are passed through setter methods. It allows changing dependencies after object creation.

• Field Injection: dependencies are injected directly into class fields, usually with annotations (e.g., @Autowired in Spring).

• Interface Injection: the class implements an interface that contains a method for passing the dependency.

Example of Setter Injection in Java:

public class Service {
    private Repository repository;

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

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

Each method has its pros and cons; the choice depends on requirements for flexibility and testability of the code.