Question

我目前正在研究实体映射，并想知道是否有没有主键用法的@OneToMany映射方法。所有映射都需要至少一个要映射的实体上的主键。

例如：我有2张桌子

Table 1
ID(PK),
Name,
Xid

Table 2
ID(PK),
UserName,
userType,
Xid

例如，我不想说

@OnetoMany(mapped by="")
public Table2 t2

@ManyToOne()
public Table1 id;

是否可以使用@JoinTable将Table1的Xid映射/关联到Table2的Xid？

Answer 1

是的，您可以将关系映射到主键和外键上。

表1：

@Entity
@Table(name = "Table1")
public class Table1 implements Serializable,Cloneable {

  @Id
  @Column(name = "id")
  private BigInteger id;     

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

  @Column(name = "Xid")
  private BigInteger xid;

  @OneToOne
  @JoinColumn(name = "Xid", nullable = false, insertable = false, updatable = false, referencedColumnName = "Xid")
  private Table2 table2;

// Getter and Setters
}

表2：

@Entity
@Table(name = "Table2")
public class Table2 implements Serializable , Cloneable {

  public Table2() {
  }

  @Column(name = "id")
  private BigInteger id;

  @Column(name = "Xid")
  private BigInteger xid;

  @Column(name = "UserName")
  private String userName;

  @Column(name = "userType")
  private String userType;
// Getter and Setters    

}

在查询中，您将指定

之类的联接

    CriteriaBuilder cb = session.getCriteriaBuilder();
    CriteriaQuery<Table1> cq = cb.createQuery(Table1.class);
    Root<Table1> root = cq.from(Table1.class);
    Join<Table1, Table2> join = (Join<Table1, Table2>) root
            .fetch(Table1_.table2);
    List<Predicate> conditions = new ArrayList<>();
    conditions.add(cb.equal(root.get(Table1_.Xid), join.get(
        Table2_.Xid)));
    cq.where(conditions.toArray(new Predicate[]{}));
    Query query= session.createQuery(cq);

将2个实体与PK和FK以外的列连接

1 个答案: