In a constructor-based DI, we saw a dependent object injecting through a constructor argument. In a setter-based DI, the dependent object is provided by a setter method in the dependent class. Setter-based DI is accomplished by calling setter methods on beans after invoking no-args constructors through the container.

In the following code, we show how to use a setter method for injecting a CustomerService object in the BankingService class:

@Component
public class BankingService {

  private CustomerService customerService;  

  // Setter-based Dependency Injection
  @Autowired
  public void setCustomerService(CustomerService customerService) {
  this.customerService = customerService;
  }

  public void showCustomerAccountBalance() {
    customerService.showCustomerAccountBalance();
  }

}