类继承

Question

在Spring配置类中可以使用继承吗？如果是的话，如何做到这一点？

例如：

@ConfigurationProperties(prefix="my-config")
public class Config {
    List<Vehicle> vehicles;
}

类(或接口) "Vehicle“有两个实现:卡车和汽车。所以YAML看起来可能是：

my.config.vehicles:
  -
    type: car
    seats: 3
  -
    type: truck
    axles: 3

Answer 1

我认为这是不可能的(至少据我所知)。但是，您可以按照以下方式设计代码：

将属性注入Builder对象

用所有属性定义一个对象，我们将其称为VehicleBuilder (或工厂，您选择它的名称)。VehicleBuilders是从Yaml注入的。然后，您可以在@PostConstruct块中检索每个构建器的车辆。守则：

@ConfigurationProperties(prefix="my-config")
@Component
public class Config {
    private List<VehicleBuilder> vehicles = new ArrayList<VehicleBuilder>();
    private List<Vehicle> concreteVehicles;
    
    public List<VehicleBuilder> getVehicles() {
        return vehicles;
    }
    
    public List<Vehicle> getConcreteVehicles() {
        return concreteVehicles;
    }

    @PostConstruct
    protected void postConstruct(){
        concreteVehicles = vehicles.stream().map(f -> f.get())
                                   .collect(Collectors.<Vehicle>toList());
    }
}

建造者：

public class VehicleBuilder {
    private String type;
    private int seats;
    private int axles;

    public Vehicle get() {
        if ("car".equals(type)) {
            return new Car(seats);
        } else if ("truck".equals(type)) {
            return new Trunk(axles);
        }
        throw new AssertionError();
    }

    public void setType(String type) {
        this.type = type;
    }

    public void setSeats(int seats) {
        this.seats = seats;
    }

    public void setAxles(int axles) {
        this.axles = axles;
    }
}