Java 根据枚举值选择服务类型

我想创建一种工厂模式，但我很挣扎

//OperationType is an Enum
public interface SettlementService<OperationType>{
    void settleOperation(Order order);
}

---

代码显然不起作用，但希望您能理解。如何实现这一点？

要使用工厂模式实现

结算服务

，您不需要在

界面

中了解泛型类型

public interface SettlementService {
    void settleOperation(Order order);
}

此外，它实现的类如下所示-

public class ClientSettlementService implements SettlementService {
    @Override
    public void settleOperation(Order order) {
        System.out.println("clients!!");
    }
}

public class CustomerSettlementService implements SettlementService {
    @Override
    public void settleOperation(Order order) {
        System.out.println("customers!!");
    }
}

然后，基于

OperationType

enum，要构建的工厂将如下所示

public class SettlementFactory {
    private SettlementService provideService(OperationType operationType) {
        switch (operationType) {
            case CLIENT:
                return new ClientSettlementService();
            case CUSTOMER:
                return new CustomerSettlementService();
            default:
                throw new UnsupportedOperationException("Unsupported operation type!");
        }
    }
}

然后，您可以使用此工厂结算给定的

订单

，如下所示：

private void settleOrder(Order order) {
    SettlementFactory settlementFactory = new SettlementFactory();
    SettlementService settlementService = settlementFactory.provideService(order.getOperationType());
    settlementService.settleOperation(order);
}

---

如果您偶然发现Factory类是开销类，并且希望将提供服务的功能简化为使用它的相同方法，则可以使用

Map

并处理提供的服务，例如：

private void settleOrder(Order order) {
    Map<OperationType, SettlementService> typeSettlementServiceMap =
            Map.of(OperationType.CLIENT, new ClientSettlementService(),
                    OperationType.CUSTOMER, new CustomerSettlementService());
    SettlementService settlementService = typeSettlementServiceMap.get(order.getOperationType());
    if (settlementService == null) throw new UnsupportedOperationException("..message..");
    settlementService.settleOperation(order);
}

private void结算订单（订单）{
地图类型结算服务地图=
Map.of（OperationType.CLIENT，new ClientSettlementService（），
OperationType.CUSTOMER，新CustomerSettlementService（））；
沉降器服务沉降器服务=类型沉降器服务映射.get（order.getOperationType（））；
如果（settlementService==null）抛出新的UnsupportedOperationException（“…消息…”）；
结算服务。结算操作（订单）；
}

在您的界面中

结算服务

在哪里使用类型绑定？我真的不知道。该类型仅用于确定我要使用的服务。

private void settleOrder(Order order) {
    SettlementFactory settlementFactory = new SettlementFactory();
    SettlementService settlementService = settlementFactory.provideService(order.getOperationType());
    settlementService.settleOperation(order);
}

private void settleOrder(Order order) {
    Map<OperationType, SettlementService> typeSettlementServiceMap =
            Map.of(OperationType.CLIENT, new ClientSettlementService(),
                    OperationType.CUSTOMER, new CustomerSettlementService());
    SettlementService settlementService = typeSettlementServiceMap.get(order.getOperationType());
    if (settlementService == null) throw new UnsupportedOperationException("..message..");
    settlementService.settleOperation(order);
}