Bettering - "Redefining the Service Layer with Groovy Categories"

CheckPaymentProcessor.groovy

class CheckPaymentProcessor {
  	static String process(PaymentType paymentType) {
		def gateway = new CheckPaymentProcessor()
		// … implementation code ...
	}
}

EmployeePaymentProcessor.groovy

class EmployeePaymentProcessor {
  	static String process(PaymentType paymentType) {
		def gateway = new EmployeePaymentGateway()
		// … implementation code ...
	}
}

GiftCardPaymentProcessor.groovy

class GiftCardPaymentProcessor {
  	static String process(PaymentType paymentType) {
		def gateway = new GiftCardPaymentGateway()
		// … implementation code ...
	}
}