CODESAMPLE

Service Locator - Java

Service Locator Java

The Service Locator pattern provides a centralized way to obtain references to services without tightly coupling the client code to the concrete service implementations. Instead of constructing dependencies directly, clients request them from a locator. This promotes loose coupling and makes it easier to swap service implementations.

The Java example implements a simple ServiceLocator class responsible for storing and retrieving services. Service is an interface that defines the functionality to be provided. Concrete services like EmailService and LoggingService implement this interface. Clients obtain services via ServiceLocator.getService(Service.class), which returns the appropriate implementation. This aligns with Java’s dependency injection principles, though it’s a less explicit form compared to using frameworks like Spring. The use of interfaces and a central access point is standard Java practice.

// Service Interface
interface Service {
    void execute();
}

// Concrete Service 1
class EmailService implements Service {
    @Override
    public void execute() {
        System.out.println("Sending email...");
    }
}

// Concrete Service 2
class LoggingService implements Service {
    @Override
    public void execute() {
        System.out.println("Logging data...");
    }
}

// Service Locator
class ServiceLocator {
    private static final java.util.Map<Class<? extends Service>, Service> services = new java.util.HashMap<>();

    static {
        // Register services
        registerService(EmailService.class, new EmailService());
        registerService(LoggingService.class, new LoggingService());
    }

    private static void registerService(Class<? extends Service> serviceType, Service service) {
        services.put(serviceType, service);
    }

    public static <T extends Service> T getService(Class<T> serviceType) {
        return (T) services.get(serviceType);
    }
}

// Client Code
class Client {
    private Service emailService;
    private Service loggingService;

    public Client() {
        this.emailService = ServiceLocator.getService(EmailService.class);
        this.loggingService = ServiceLocator.getService(LoggingService.class);
    }

    public void doSomething() {
        emailService.execute();
        loggingService.execute();
    }
}

// Main Class to run the example
public class Main {
    public static void main(String[] args) {
        Client client = new Client();
        client.doSomething();
    }
}