danveloper

class LocalPaymentService implements PaymentService {
  
	// Dependency injected from container
	CreditCardPaymentGateway creditCardPaymentGateway
	GiftCardPaymentGateway giftCardPaymentGateway
	CheckPaymentGateway checkPaymentGateway
	EmployeePaymentGateway employeePaymentGateway

	public String process(PaymentType paymentType) throws IllegalArgumentException {
		if (paymentType instanceof CreditCardPaymentType) {

danveloper

class CreditCardPaymentProcessor {
        static {
            CreditCardPaymentProcessor.metaClass.static.methodMissing = { String name, args ->
                if (name.startsWith("getGatewayFor")) {
                    def state = name.replaceAll("getGatewayFor","")?.toLowerCase()
                    switch (state) {
                        case "ca":
                            return new CheckPaymentProcessor()
                        default:
                            return new CreditCardPaymentProcessor()

danveloper

class LocalPaymentService implements PaymentService {

  	public String process(PaymentType paymentType) {
		if (paymentType instanceof CreditCardPaymentType) {
			use (CreditCardPaymentProcessor) {
				return paymentType.process()
			}
		}
		// ...
	}

danveloper

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

danveloper

class PaymentTypeHandlerRegistrationCategory {
  	static final registry = [:]

	// type => handler registration
	static def register(Class type, Class handler) {
		registry[type] = handler
	}

	static def getHandler(Class type) {
		registry[type]

danveloper

class LocalPaymentService implements PaymentService {
  	static {
		use (PaymentTypeHandlerRegistrationCategory) {
			CreditCardPaymentType.register(CreditCardPaymentProcessor)
			GiftCardPaymentType.register(GiftCardPaymentProcessor)
			EmployeePaymentType.register(EmployeePaymentProcessor)
			CheckPaymentType.register(CheckPaymentProcessor)
		}
	}

danveloper

class LocalPaymentService implements PaymentService {
  	static {
		use (PaymentTypeHandlerRegistrationCategory) {
			CreditCardPaymentType.register(CreditCardPaymentProcessor)
			GiftCardPaymentType.register(GiftCardPaymentProcessor)
			EmployeePaymentType.register(EmployeePaymentProcessor)
			CheckPaymentType.register(CheckPaymentProcessor)
		}
	}

danveloper

package com.objectpartners.groovy.ext;

import groovy.lang.MetaClass;
import groovy.lang.MetaClassRegistry;
import org.codehaus.groovy.runtime.GeneratedClosure;
import org.codehaus.groovy.runtime.metaclass.ClosureMetaClass;

class CustomMetaClassCreationHandle extends MetaClassRegistry.MetaClassCreationHandle {

    protected MetaClass createNormalMetaClass(Class theClass,MetaClassRegistry registry) {

danveloper

package com.objectpartners.groovy.ext;

// imports...

class MixinResolvingMetaClass extends MetaClassImpl {
    static final Map<Class, Class> cachedMixins = new ConcurrentHashMap<>();

    MixinResolvingMetaClass(MetaClassRegistry registry, Class theClass) {
        super(registry, theClass);
    }

danveloper

package groovy.runtime.metaclass.java.lang

import groovy.json.JsonSlurper

class StringMixins {

    // Must be static & must take an instance of the receiver as the first vararg
    static def toJson(String input) {
        new JsonSlurper().parseText(input)
    }