Business Delegate Pattern

The Business Delegate acts as a client-side business abstraction, it provides an abstraction for, and thus hides, the implementation of the business services. It reduces the coupling between presentation-tier clients and the system’s Business services.

UML Diagram Business Delegate Pattern

Design components

• 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.

Let’s see an example of Business Delegate Pattern.

Java

interface BusinessService
{
    public void doProcessing();
}

class OneService implements BusinessService
{
    public void doProcessing()
    {
        System.out.println("Processed Service One");
    }
}

class TwoService implements BusinessService
{
    public void doProcessing()
    {
        System.out.println("Processed Service Two");
    }
}

class BusinessLookUp
{
    public BusinessService getBusinessService(String serviceType)
    {
        if(serviceType.equalsIgnoreCase("One"))
        {
            return new OneService();
        }
        else
        {
            return new TwoService();
        }
   }
}

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();
    }
}

class Client
{
    BusinessDelegate businessService;

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

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

class BusinessDelegatePattern
{
    public static void main(String[] args)
    {
        BusinessDelegate businessDelegate = new BusinessDelegate();
        businessDelegate.setServiceType("One");

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

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

Output:

Processed Service One
Processed Service Two

Advantages :

• Business Delegate reduces coupling between presentation-tier clients and Business services.
• The Business Delegate hides the underlying implementation details of the Business service.

Disadvantages :

• Maintenance due the extra layer that increases the number of classes in the application.

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