// 业务服务接口
public interface BusinessService {
    void doProcessing();
}

// 具体业务服务实现
public class EJBService implements BusinessService {
    @Override
    public void doProcessing() {
        System.out.println("Processing task by invoking EJB Service");
    }
}

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

// 业务查询服务
public class BusinessLookUp {
    public BusinessService getBusinessService(String serviceType) {
        if(serviceType.equalsIgnoreCase("EJB")) {
            return new EJBService();
        } else {
            return new JMSService();
        }
    }
}

// 业务代表
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();
    }
}

// 客户端
public class Client {
    BusinessDelegate businessService;

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

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