簡(jiǎn)介

業(yè)務(wù)代表模式（Business Delegate Pattern）用于對(duì)表示層和業(yè)務(wù)層解耦值纱。它基本上是用來(lái)減少通信或?qū)Ρ硎緦哟a中的業(yè)務(wù)層代碼的遠(yuǎn)程查詢功能。在業(yè)務(wù)層中我們有以下實(shí)體柜去。

• 客戶端（Client） - 表示層代碼可以是 JSP、servlet 或 UI java 代碼。
• 業(yè)務(wù)代表（Business Delegate） - 一個(gè)為客戶端實(shí)體提供的入口類播赁，它提供了對(duì)業(yè)務(wù)服務(wù)方法的訪問(wèn)拟枚。
• 查詢服務(wù)（LookUp Service） - 查找服務(wù)對(duì)象負(fù)責(zé)獲取相關(guān)的業(yè)務(wù)實(shí)現(xiàn)薪铜，并提供業(yè)務(wù)對(duì)象對(duì)業(yè)務(wù)代表對(duì)象的訪問(wèn)。
• 業(yè)務(wù)服務(wù)（Business Service） - 業(yè)務(wù)服務(wù)接口恩溅。實(shí)現(xiàn)了該業(yè)務(wù)服務(wù)的實(shí)體類隔箍，提供了實(shí)際的業(yè)務(wù)實(shí)現(xiàn)邏輯。

實(shí)現(xiàn)

創(chuàng)建 Client脚乡、BusinessDelegate蜒滩、BusinessService、LookUpService奶稠、JMSService 和 EJBService 來(lái)表示業(yè)務(wù)代表模式中的各種實(shí)體俯艰。演示類BusinessDelegatePatternDemo使用 BusinessDelegate 和 Client 來(lái)演示業(yè)務(wù)代表模式的用法。

業(yè)務(wù)代表模式

代碼實(shí)現(xiàn)

//創(chuàng)建 BusinessService 接口锌订。
//BusinessService.java
public interface BusinessService {
   public void doProcessing();
}
//創(chuàng)建實(shí)體服務(wù)類蟆炊。
//EJBService.java
public class EJBService implements BusinessService {
 
   @Override
   public void doProcessing() {
      System.out.println("Processing task by invoking EJB Service");
   }
}
//JMSService.java
public class JMSService implements BusinessService {
 
   @Override
   public void doProcessing() {
      System.out.println("Processing task by invoking JMS Service");
   }
}
//創(chuàng)建業(yè)務(wù)查詢服務(wù)。
//BusinessLookUp.java
public class BusinessLookUp {
   public BusinessService getBusinessService(String serviceType){
      if(serviceType.equalsIgnoreCase("EJB")){
         return new EJBService();
      }else {
         return new JMSService();
      }
   }
}
//創(chuàng)建業(yè)務(wù)代表瀑志。
//BusinessDelegate.java
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();     
   }
}
//創(chuàng)建客戶端涩搓。
//Client.java
public class Client {
   
   BusinessDelegate businessService;
 
   public Client(BusinessDelegate businessService){
      this.businessService  = businessService;
   }
 
   public void doTask(){      
      businessService.doTask();
   }
}
//使用 BusinessDelegate 和 Client 類來(lái)演示業(yè)務(wù)代表模式污秆。
//BusinessDelegatePatternDemo.java
public class BusinessDelegatePatternDemo {
   
   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();
   }
}
//執(zhí)行程序，輸出結(jié)果：

Processing task by invoking EJB Service
Processing task by invoking JMS Service