package com.interview.design.pattern.j2ee;

/**
 * Created_By: stefanie
 * Date: 14-12-3
 * Time: 下午6:22
 *
 * Business Delegate Pattern is used to decouple presentation tier and business tier.
 * It is basically use to reduce communication or remote lookup functionality to business tier code in presentation tier code.
 * In business tier we've following entities.
 *
 * Client - Presentation tier code may be JSP, servlet or UI java code.
 * Business Delegate - A single entry point class for client entities to provide access to Business Service methods.
 * LookUp Service - Lookup service object is responsible to get relative business implementation and
 *                  provide business object access to business delegate object.
 * Business Service - Business Service interface. Concrete classes implements this business service to
 *                    provide actual business implementation logic.
 */
public class BusinessDelegationPattern {
    static interface BusinessService {
        public void doProcessing();
    }
    static class EJBService implements BusinessService {

        @Override
        public void doProcessing() {
            System.out.println("Processing task by invoking EJB Service");
        }
    }

    static class JMSService implements BusinessService {

        @Override
        public void doProcessing() {
            System.out.println("Processing task by invoking JMS Service");
        }
    }

    static class BusinessLookUp {
        public BusinessService getBusinessService(String serviceType){
            if(serviceType.equalsIgnoreCase("EJB")){
                return new EJBService();
            }else {
                return new JMSService();
            }
        }
    }

    static class BusinessDelegate {
        private BusinessLookUp lookupService = new BusinessLookUp();
        private BusinessService businessService;
        private String serviceType;

        public void setServiceType(String serviceType){
            this.serviceType = serviceType;
        }

        public void doTask(){
            businessService = lookupService.getBusinessService(serviceType);
            businessService.doProcessing();
        }
    }

    static class Client {

        BusinessDelegate businessService;

        public Client(BusinessDelegate businessService){
            this.businessService  = businessService;
        }

        public void doTask(){
            businessService.doTask();
        }
    }

    public static void main(String[] args) {

        BusinessDelegate businessDelegate = new BusinessDelegate();
        businessDelegate.setServiceType("EJB");

        Client client = new Client(businessDelegate);
        client.doTask();

        businessDelegate.setServiceType("JMS");
        client.doTask();
    }
}