如何在JPA中初始化模型

Question

我只是尝试通过JPA查询初始化列表中的对象。到目前为止，我在1个半天的行程中没有成功。

public interface Po_partRepository extends JpaRepository<Po_part, Long> {
  @Query(value = "SELECT " + "po.id po_id," + "po.po_number po_number,"
    + "po.due_date po_due_date," + "po_part.id po_part_id,"
    + "po_part.part_quantity part_quantity," + "part.id part_id,"
     + "part.part_number part_number,"
    + "part.part_description part_description,"
    + "part.plasma_hrs_per_part plasma_hrs,"
    + "part.grind_hrs_per_part grind_hrs,"
    + "part.mill_hrs_per_part mill_hrs,"
    + "part.brakepress_hrs_per_part brakepress_hrs "
    + "FROM hillcresttooldie.t_po po "
    + "join hillcresttooldie.t_po_part po_part "
    + "on po_part.po_id = po.id " + "join hillcresttooldie.t_part part "
    + "on part.id = po_part.part_id;", nativeQuery = true)
List<Shop_Orders> getShopOrders(); }

Shop_Orders模型

@Entity
@Table(name = "SHOP_ORDERS")
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Shop_Orders implements Serializable {

/**
 * 
 */
private static final long serialVersionUID = 799464578815300087L;

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int shop_order_id;

@Column(name = "po_id")
private int po_id;

@Column(name = "po_number")
private int po_number;

@Column(name = "po_date")
private Date po_due_date;

@Column(name = "part_quanity")
private int part_quanity;

@Column(name = "part_id")
private int part_id;

@Column(name = "part_description")
private String part_description;

@Column(name = "plasma_hrs")
private int plasma_hrs;

@Column(name = "grind_hrs")
private int grind_hrs;

@Column(name = "mill_hrs")
private int mill_hrs;

@Column(name = "breakpress_hrs")
private int breakpress_hrs;

public Shop_Orders() {

}

public int getPo_id() {
    return po_id;
}

我为shop_orders创建了表：

以下是运行查询并在列表中设置对象后我想要执行的操作的示例。

Shop_Orders shopOrders;
int poNumber = shopOrders.getPo_number(); 

但是，当我运行查询时，我一直收到以下错误

[ERROR] com.htd.aop.logging.LoggingAspect - Exception in 
com.htd.web.rest.Po_partResource.getAll() with cause = null
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to 
com.htd.repository.Shop_Orders
at com.htd.web.rest.Po_partResource.getAll(Po_partResource.java:85) ~  
[classes/:na]

我会发布Po.java和Part.java的片段，以防有人想看看它们。

/**
* A Po.
*/
@Entity
@Table(name = "T_PO")
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Po implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "po_number")
    private String po_number;

part.java

/**
 * A Part.
 */
@Entity
@Table(name = "T_PART")
@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Part implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "part_number")
    private String part_number;

提前感谢您的建议。

Answer 1

如果您的表格中包含与您的Shop_orders实体相对应的数据，那么您的查询应该是：

@Query("SELECT so FROM Shop_Orders so")

由于您已将Shop_Orders实体映射到该表。

但是，由于您似乎正在构建所涉及的3个表的反规范化模型（PO，Part和两者之间的连接表，PO_Part），那么您可能需要为此创建一个非规范化的数据库VIEW。您拥有的原始查询，然后通过在Shop_Orders注释中指定该视图，将该视图映射到您的@Table实体。

或者，您可以为Shop_Orders创建一个构造函数（不需要是JPA实体），它可以获取所有列。换句话说：

public Shop_Orders(int po_id, int po_number, Date po_due_date, etc... )

然后，假设您有Po_Part和Po之间的联接表的实体Part（请参阅my answer to your other question），查询可以是：

@Query("SELECT new Shop_Orders(po.id, po.po_number, "
        + "po.due_date, po_part.id, po_part.part_quantity, "
        + "part.id, part.part_number, part.part_description "
        + "part.plasma_hrs_per_part, part.grind_hrs_per_part, "
        + "part.mill_hrs_per_part, part.brakepress_hrs_per_part) "
        + "FROM Po po LEFT JOIN po.partList po_part "
        + "LEFT JOIN po_part.part");

这也假设Po的{​​{1}}集合称为Po_Part。

您很可能必须完全打包partList类。

顺便说一句，我建议您不要使用复数命名您的JPA实体类。换句话说，您的实体类应该被称为Shop_Orders（或可能是Shop_Order），因为此类的每个实例仅代表一个商店订单。