Concrete Dependency Injection (ARCH4199)

Key java.quality.concrete-dependency · Severity info · Category quality

Constructor dependencies typed as concrete classes violate the dependency inversion principle; they pin the implementation and make test doubles harder to use. Depend on an interface.

Incorrect

@Service
class CheckoutService {
    private final StripePaymentGateway gateway;
    CheckoutService(StripePaymentGateway gateway) { this.gateway = gateway; }
}

Correct

@Service
class CheckoutService {
    private final PaymentGateway gateway;
    CheckoutService(PaymentGateway gateway) { this.gateway = gateway; }
}

Fix

Type the dependency as an interface/abstraction rather than a concrete class.