Design Pattern 简明教程

Design Patterns - Business Delegate Pattern

业务委托模式用于将表示层和业务层解耦。它基本上用于减少表示层代码对业务层代码的通信或远程查找功能。在业务层中，我们有以下实体：

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 have 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 implement this business service to provide actual business implementation logic.

Implementation

我们将创建 Client、BusinessDelegate、BusinessService、LookUpService、JMSService 和 EJBService 来表示业务委托模式的不同实体。

We are going to create a Client, BusinessDelegate, BusinessService, LookUpService, JMSService and EJBService representing various entities of Business Delegate patterns.

BusinessDelegatePatternDemo（我们的演示类）将使用 BusinessDelegate 和 Client 来演示业务委托模式。

BusinessDelegatePatternDemo, our demo class, will use BusinessDelegate and Client to demonstrate use of Business Delegate pattern.

Step 1

创建 BusinessService 界面。

Create BusinessService Interface.

BusinessService.java

public interface BusinessService {
   public void doProcessing();
}

Step 2

创建具体的 Service 类。

Create concrete Service classes.

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");
   }
}

Step 3

创建业务查找服务。

Create Business Lookup Service.

BusinessLookUp.java

public class BusinessLookUp {
   public BusinessService getBusinessService(String serviceType){

      if(serviceType.equalsIgnoreCase("EJB")){
         return new EJBService();
      }
      else {
         return new JMSService();
      }
   }
}

Step 4

创建业务委托。

Create Business Delegate.

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();
   }
}

Step 5

创建客户端。

Create Client.

Client.java

public class Client {

   BusinessDelegate businessService;

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

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

Step 6

使用 BusinessDelegate 和 Client 类演示业务委托模式。

Use BusinessDelegate and Client classes to demonstrate Business Delegate pattern.

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();
   }
}

Step 7

验证输出。

Verify the output.

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