package com.study.dp.business.delegate;public interface BusinessService {public void doProcessing();}

EJBService类：业务的实际实现方式一

package com.study.dp.business.delegate;public class EJBService implements BusinessService {@Overridepublic void doProcessing() {System.out.println("Processing task by invoking EJB Service");}}

JMSService类：业务的实际实现方式二

package com.study.dp.business.delegate;public class JMSService implements BusinessService {@Overridepublic void doProcessing() {System.out.println("Processing task by invoking JMS Service");}}

BusinessLookUp类：业务查询类，有点类似于业务实现的工厂模式

package com.study.dp.business.delegate;public class BusinessLookUp {public BusinessService getBusinessService(String serviceType) {if(serviceType.equalsIgnoreCase("EJB")) {return new EJBService();}else {return new JMSService();}}}

BusinessDelegate类：业务代表类，向客户端提供调用接口

package com.study.dp.business.delegate;public 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();}
}

Client类：客户端

package com.study.dp.business.delegate;public class Client {BusinessDelegate businessService;public Client(BusinessDelegate businessService) {this.businessService = businessService;}public void doTask() {businessService.doTask();}}

Demo类：测试类

package com.study.dp.business.delegate;public class Demo {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();}}

四、应用场景