服务定位器模式

//serviceLocator
interface Service
{
    public function getName();
    public function execute();
}

class Service1 implements Service
{
    public function execute()
    {
        echo 'Executing Service1' . "<br />";
    }
    
    public function getName()
    {
        return "Service1" . "<br />";
    }
}

class Service2 implements Service
{
    public function execute()
    {
        echo 'Executing Service2' . "<br />";
    }
    
    public function getName()
    {
        return "Service2" . "<br />";
    }
}



class InitialContext
{
    public function lookup($jndiName)
    {
        //返回0就是相等
        if (!strcasecmp('SERVICE1', $jndiName)) {
            echo "Looking up and creating a new Service1 object" . "<br />";
            return new Service1();
        } else if (!strcasecmp('SERVICE2', $jndiName)) {
            echo "Looking up and creating a new Service2 object" . "<br />";
            return new Service2();
        }
        return null;
    }
}

class Cache
{
    private $services;
    
    public function Cache()
    {
        $this->services = [];
    }
    
    public function getService($serviceName)
    {
        foreach ($this->services as $service) {
            if (!strcasecmp($service->getName(), $serviceName)) {
                echo 'Returning cached  ' . $serviceName . ' object' . "<br />";
                return $service;
            }
        }
        return null;
    }
    
    public function addService($newService)
    {
        $exists = false;
        foreach ($this->services as $service) {
            if(!strcasecmp($service->getName(),$newService->getName())){
            $exists = true;
         }
        }
        
        if ($exists) {
            $this->services[] = $newService;
        }
    }
}



class ServiceLocator
{
    private static $cache = null;
    
    public function __construct()
    {
        if (self::$cache == null) {
            self::$cache = new Cache();
        }
    }
    
    public function getService($jndiName)
    {
        $service = self::$cache->getService($jndiName);
        
        if ($service != null) {
            return $service;
        }
        
        $context = new InitialContext();
        $service1 = $context->lookup($jndiName);
        self::$cache->addService($service1);
        return $service1;
    }
}

$ServiceLocator = new ServiceLocator;

$service = $ServiceLocator->getService("Service1");
$service->execute();

$service = $ServiceLocator->getService("Service2");
$service->execute();


$service = $ServiceLocator->getService("Service1");
$service->execute();

$service = $ServiceLocator->getService("Service2");
$service->execute();

参考文章 http://www.runoob.com/design-pattern/service-locator-pattern.html