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Pavel
Asked:2020-07-13 20:43:59 +0000 UTC2020-07-13 20:43:59 +0000 UTC

Stratery模式的功能接口应用

  • 772

mapstruct 上有一个映射器，它根据票证的类型调用不同的 map 方法，所有这些都是通过 if else 条件实现的。我试图在策略模式或类似的东西上重写它，但在这种情况下，某些东西不会一直收敛。

// Хотелось бы как-то на месте инициализировать список условий
Map<Set<TicketType>, Function<TicketRequestDto, Ticket>> ticketMapStrategies = new ConcurrentHashMap<>(
    ... Как-то наполнить на месте, но как? ...
);


default Ticket ticketRequestDtoToTicket(TicketRequestDto dto) {
    TicketType type = dto.getType();

    if (type.equals(TicketType.EMERGENCY_STOP) || type.equals(TicketType.SETTING_UPLOAD)
            || dto.getType().equals(TicketType.SETTING_DOWNLOAD)) {
        return ticketEmergencyStopRequestDtoToTicket(dto);
    } else if (type.equals(TicketType.DEPOSIT_INCOME) || type.equals(TicketType.DEPOSIT_OUTCOME)) {
        return ticketAccountTransferRequestDtoToTicket(dto);
    } else if (type.equals(TicketType.PARTNER_REQUEST)) {
        return ticketPartnershipRequestDtoToTicket(dto);
    } else {
        return ticketInfoRequestDtoToTicket(dto);
    }
}

@Mapping(target = "instance.id", source = "instanceId")
@Mapping(target = "recipient.id", source = "recipientId")
Ticket ticketEmergencyStopRequestDtoToTicket(TicketRequestDto dto);

@Mapping(target = "account.id", source = "accountId")
@Mapping(target = "recipient.id", source = "recipientId")
Ticket ticketAccountTransferRequestDtoToTicket(TicketRequestDto dto);

@Mapping(target = "sender.id", source = "senderId")
@Mapping(target = "recipient.id", source = "recipientId")
Ticket ticketPartnershipRequestDtoToTicket(TicketRequestDto dto); 

Ticket ticketInfoRequestDtoToTicket(TicketRequestDto dto);

我想以某种方式在现场初始化条件列表，然后ticketRequestDtoToTicket按键获取。就像是：

    Set<TicketType> key = ticketMapStrategies.keySet().stream()
            .filter(set -> set.contains(dto.getType()))
            .findFirst()
            .orElse(new HashSet<>());
    return ticketMapStrategies.get(key).apply(dto);

如果可能的话，或者更紧凑的东西。

嗯，或者类似的东西。鉴于所有这些都发生在接口中，如何实现这一点？

爪哇 11

java

2 个回答

  1. 只要有我，ConcurrentHashMap你就不需要——你不要在几个线程中添加到地图中。

    它可以是这样的（如果 java11+）

    Map<Set<TicketType>, Function<TicketRequestDto, Ticket>> map = Map.of(
    Set.of(TicketType.EMERGENCY_STOP, TicketType.SETTING_UPLOAD, TicketType.SETTING_DOWNLOAD), this::ticketEmergencyStopRequestDtoToTicket,
    Set.of(TicketType.DEPOSIT_INCOME, TicketType.DEPOSIT_OUTCOME), this::ticketAccountTransferRequestDtoToTicket,
    Set.of(TicketType.PARTNER_REQUEST), this::ticketPartnershipRequestDtoToTicket
);

default Ticket ticketRequestDtoToTicket(TicketRequestDto dto) {
    return map.entrySet()
       .stream()
       .filter(entry -> entry.getKey().contains(dto.getType))
       .map(entry -> entry.getValue())
       .findFirst()
       .orElseGet(this::ticketInfoRequestDtoToTicket)
       .apply(dto);
}

    如果你有java8，那么你可以就地初始化

    Map<Set<TicketType>, Function<TicketRequestDto, Ticket>> map = new HashMap() {{
    map.put(new HashSet(Arrays.asList(перечислить нужные типы тикета)), this::ticketEmergencyStopRequestDtoToTicket);
    //вставить все остальные подобным способом.
}}

    如果 guava 连接到项目，那么 ImmutableMap 可以在那里使用：

    Map<Set<TicketType>, Function<TicketRequestDto, Ticket>> map = ImmutableMap.of(
    new HashSet(Arrays.asList(перечислить нужные типы тикета)), this::ticketEmergencyStopRequestDtoToTicket),
    // добавить все остальное
);

    PS 一般来说，这里其实不需要map作为结构体——我们从不调用.get()map上的方法=>这里不需要map作为结构体。它可以很容易地替换为对列表 ( List<Pair<Set<TicketType>, Function<TicketRequestDto, Ticket>>>)

    • 1
  2. Best Answer

    到目前为止，我发现的最可接受的选择是使用@PostConstruct并填写其中的地图。

    Map<Set<TicketType>, Function<TicketRequestDto, Ticket>> ticketMapStrategies = new ConcurrentHashMap<>();

@PostConstruct
default void init() {
    ticketMapStrategies.put(
            Set.of(TicketType.INFO),
            this::ticketInfoRequestDtoToTicket);
    ticketMapStrategies.put(
            Set.of(TicketType.PARTNER_REQUEST),
            this::ticketPartnershipRequestDtoToTicket);
    ticketMapStrategies.put(
            Set.of(TicketType.DEPOSIT_INCOME, TicketType.DEPOSIT_OUTCOME),
            this::ticketAccountTransferRequestDtoToTicket);
    ticketMapStrategies.put(
            Set.of(TicketType.EMERGENCY_STOP, TicketType.SETTING_UPLOAD, TicketType.SETTING_DOWNLOAD),
            this::ticketEmergencyStopRequestDtoToTicket);
}

default Ticket ticketRequestDtoToTicket(TicketRequestDto dto) {
    Set<TicketType> key = ticketMapStrategies.keySet().stream()
            .filter(set -> set.contains(dto.getType())).findFirst()
            .orElseThrow(UnsupportedTicketTypeException::new);
    return ticketMapStrategies.get(key).apply(dto);
}
    • 1

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