java - 尝试遍历实体 ID 时出现 ClassCastException : Integer cannot be cast to Long,

Question

我的服务中有以下方法:

public Set<BoardCard> moveHoldedCardsToNewBoard(Board newBoard, Board prevBoard) {
        Set<BoardCard> boardCards = new HashSet<>();
        if (prevBoard != null) {
            List<Long> holdedCardIds = getExcludedCardIds(prevBoard);
            for (Long item: holdedCardIds) {

            }
    }

当我想循环 holdedCardIds 列表时，我收到:java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long 在这个地方 -> for (Long item: holdedCardIds) {

我的 getExcludedCardIds() 看起来像:

@Override
public List<Long> getExcludedCardIds(Board board) {

        return boardCardRepository.getExcludedCardIds(board.getId());
    }

存储库:

@Repository
public interface BoardCardRepository extends JpaRepository<BoardCard, Long>, QueryDslPredicateExecutor<BoardCard> {

    @Query(value = "SELECT bc.card_id FROM boards_cards bc WHERE bc.board_id =:boardId AND bc.on_hold=true", nativeQuery = true)
    List<Long> getExcludedCardIds(@Param("boardId") Long boardId);
}

实体:

@Entity
@NamedEntityGraph(name = "graph.BoardCard", attributeNodes = {})
@Table(name = "boards_cards")
public class BoardCard implements Serializable {

    private static final long serialVersionUID = -9019060375256960701L;

    @EmbeddedId
    private BoardCardId id = new BoardCardId();

}
@Embeddable
public class BoardCardId implements Serializable {

    private static final long serialVersionUID = -3630484760647866357L;

    @ManyToOne
    private Board board;

    @ManyToOne
    private Card card;
}

    @Entity
    @Table(name = "boards")
    public class Board extends BaseEntity implements Serializable {
        @Id
        @SequenceGenerator(name = "boards_id_seq", sequenceName = "boards_id_seq", allocationSize = 1)
        @GeneratedValue(strategy = GenerationType.AUTO, generator = "boards_id_seq")
        private Long id;
}




 @Entity    
   @Table(name = "cards")     
   public class Card extends BaseEntity implements Serializable {

                @Id
                @SequenceGenerator(name = "cards_id_seq", sequenceName = "cards_id_seq", allocationSize = 1)
                @GeneratedValue(strategy = GenerationType.AUTO, generator = "cards_id_seq")
                private Long id;
}

在我的 POSTGRES schema.sql 中定义了 BoardCard 实体，如下所示:

CREATE TABLE IF NOT EXISTS boards_cards(
                board_id INTEGER,
                card_id INTEGER,
                on_hold BOOLEAN DEFAULT FALSE,
                CONSTRAINT pk_user_card PRIMARY KEY (board_id, card_id),
                FOREIGN KEY(board_id) REFERENCES boards(id),
                FOREIGN KEY(card_id) REFERENCES cards(id)
            );

我找到了 here ，在 postgresql 中相当于 LONG 类型的是 bigint 。但是，如果我尝试使用它，它将如何影响我的应用程序的性能？

那么，告诉我如何解决这个问题？

Answer 1

(long) can be casted into (int), and (int) can be casted to (long)

但是，

(Long) **cannot** be casted into (Integer)

反之亦然，因为它们不是原语。 bigint

也是如此

这是您的根本问题，但我不确定它在您的程序中的哪个位置导致转换。