在表示层和业务层之间添加了一个抽象层。用于解耦表示层和业务层。
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interface BusinessService 
{
    public function handle();
}

class ConcreteBusinessService implements BusinessService
{
    public function handle()
    {
    echo 'Service : handle';
    }
}

class BusinessDelegate
{
    private $serviceType;

    public function setServiceType(String $serviceType)
    {
        $this->serviceType = $serviceType;
    }

    public function handle()
    {
        // 这里可以写成一个查询服务，为了方便理解，写具体服务在这里
        if ($this->serviceType) {}
        $businessService = new ConcreteBusinessService();
        $businessService->handle();    
    }
}

class Client
{
    private  $businessService;

    public function __construct(BusinessDelegate $businessService)
    {
        $this->businessService = $businessService;
    }

    public function handle()
    {
        $this->businessService->handle();
    }
}

$businessDelegate = new BusinessDelegate();
$businessDelegate->setServiceType("EJB");
$client = new Client($businessDelegate);
$client->handle();Copy