Question

我的服务中有以下方法：

<?php 

   include 'users_db.php';

   $first1=$_POST['name1'];
   $last1=$_POST['lastname1'];
   $username1=$_POST['user1'];
   $pass1=$_POST['password1'];
   $email01=$_POST['email1']; 

   $userinfo = $conn->prepare("INSERT INTO registered_users (FirstName, LastName, Username, Password, Email) VALUES (?, ?, ?, ?, ?)");
   $userinfo->bind_param("sssss",$first1,$last1,$username1,$pass1,$email01);

   $userinfo->execute();

    // you shoud close the prep statement object
   $userinfo->close();
   //this is the way to kill the conn
   $conn->close();
?>

当我想循环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) { } }列表时，我收到： java.lang.ClassCastException：java.lang.Integer无法在此处强制转换为java.lang.Long - ＆GT; holdedCardIds

我的getExcludedCardIds（）看起来像是：

for (Long item: holdedCardIds) {

存储库：

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

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

的entites：

@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);
}

在我的POSTGRES schema.sql中，BoardCard实体的定义如下：

@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;
}

我找到here，postgresql中等效的LONG类型为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) );。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方面？

那么，请告诉我该如何解决这个问题？

Answer 1

我找到了解决方案here。解决方案是使用 JPQL查询而不是SQL查询。

重构存储库：

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

    @Query(value = "SELECT id.card.id FROM BoardCard WHERE id.board.id = :boardId AND onHold = true")
    List<Long> getExcludedCardIds(@Param("boardId") Long boardId);
}

Answer 2

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

然而，

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

反之亦然，因为它们不是原始的。同样适用于bigint

这是你的根本问题，虽然我不确定你的程序在哪里造成演员。

Answer 3

如果您使用的是java-8，只需将Integer个对象列表转换为包含相同值的对象，然后在long中进行自动编码，即可解决此问题通过java。

getExcludedCardIds(prevBoard).stream
                             .mapToLong(x -> x).collect(Collectors.toList);

ClassCastException：尝试迭代实体ID时，无法将Integer强制转换为Long

3 个答案: