Factory Design Pattern with Spring Boot

Factory design pattern is a structure based on creating a class.

Implementation

We're going to create a Car interface and concrete classes implementing the Car interface.(Cabrio, Sedan, Hatchback) A factory class CarFactory is defined as a next step. (This class to get a Car object)

Step 1

Create an interface.

public interface Car {
    String getType();
}

Step 2

Create concrete classes(Cabrio, Sedan, Hatchback) implementing the Car interface.

public class Cabrio implements Car{
    @Override
    public String getType() {
        return "Cabrio Car has produced.";
    }
}

. . .

Step 3

Create a Factory to generate object of concrete class based. There is a list of cars and a hashmap in this factory class. In this hashmap put car class and list of cars.

@Component
public class CarFactory {
    @Autowired
    private List<Car> cars;
    private static final HashMap<Class, Car> carHashMap = new HashMap<>();
    @PostConstruct
    public void initCarFactory() {
        for (Car car : cars) {
            carHashMap.put(car.getClass(), car);
        }
    }
    public static Car getCar(String name) {
        return carHashMap.get(carHashMap.keySet().stream()
                .filter(carClass -> carClass.getSimpleName().equalsIgnoreCase(name))
                .findFirst()
                .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND, "Car not found")));
    }
}

Step 4

When all this is set, we'll create a CarService class that will provide us with an implementation of CarFactory depending on the argument that we supply to the getCar() method:

@Service
public class CarService {
    private static final Logger logger = LoggerFactory.getLogger(CarService.class);
    public String getType(String name) {
        Car car = CarFactory.getCar(name);
        logger.info("Result : {}", car.getType());
        return car.getType();
    }
}

Step 5

Publish a rest controller.

@RestController
public class CarController {
    @Autowired
    private CarService carService;
    @GetMapping(value = "api/car/{name}")
    public String getType(@PathVariable String name) {
        return carService.getType(name);
    }
}

Run it

gradlew build

Testing

curl -X GET http://localhost:8080/api/car/{name}

Example:

curl -X GET http://localhost:8080/api/car/cabrio

Example

Input : cabrio

Output : Cabrio Car has produced.