32) service locator design pattern

import java.util.ArrayList;
import java.util.List;

public class ServiceLocatorPatternDemo {

    public static void main(String[] args) {
        Service service = ServiceLocator.getService("Service1");
        service.execute();
        service = ServiceLocator.getService("Service2");
        service.execute();
        service = ServiceLocator.getService("Service1");
        service.execute();
        service = ServiceLocator.getService("Service2");
        service.execute();

    }

}

interface Service {
    public String getName();

    public void execute();
}

class Service1 implements Service {
    public void execute() {
        System.out.println("Executing Service1");
    }

    @Override
    public String getName() {
        return "Service1";
    }
}

class Service2 implements Service {
    public void execute() {
        System.out.println("Executing Service2");
    }

    @Override
    public String getName() {
        return "Service2";
    }
}

class InitialContext {
    public Object lookup(String jndiName) {
        if (jndiName.equalsIgnoreCase("SERVICE1")) {
            System.out.println("Looking up and creating a new Service1 object");
            return new Service1();
        } else if (jndiName.equalsIgnoreCase("SERVICE2")) {
            System.out.println("Looking up and creating a new Service2 object");
            return new Service2();
        }
        return null;
    }
}

class Cache {
    private List<Service> serviceList;

    public Cache() {
        serviceList = new ArrayList<Service>();
    }

    public Service getService(String serviceName) {
        for (Service service : serviceList) {
            if (service.getName().equalsIgnoreCase(serviceName)) {
                System.out.println("Returning cached " + serviceName + " object");
                return service;
            }
        }
        return null;
    }

    public void addService(Service newService) {
        boolean exists = false;
        for (Service service : serviceList) {
            if (service.getName().equalsIgnoreCase(newService.getName())) {
                exists = true;
            }
        }
        if (!exists) {
            serviceList.add(newService);
        }
    }
}

class ServiceLocator {
    private static Cache cache;
    static {
        cache = new Cache();
    }

    public static Service getService(String jndiName) {
        Service service = cache.getService(jndiName);
        if (service != null) {
            return service;
        }
        InitialContext context = new InitialContext();
        Service service1 = (Service) context.lookup(jndiName);
        cache.addService(service1);
        return service1;
    }
}

Looking up and creating a new Service1 object
Executing Service1
Looking up and creating a new Service2 object
Executing Service2
Returning cached Service1 object
Executing Service1
Returning cached Service2 object
Executing Service2