java - Hibernate Fetch 不再是 Join 的子类型

Question

我正在使用具有动态条件的 Hibernate 5.2.10，发现 Fetch 不再可分配给 Join。

在下一个示例中，我需要在同一查询中获取组数据，但我还需要使用组的字段进行排序或限制。

CriteriaBuilder cb = session.getCriteriaBuilder();
CriteriaQuery<GroupAssignment> query = cb.createQuery(GroupAssignment.class);

Root<GroupAssignment> root = query.from(GroupAssignment.class);
SingularAttributeJoin<GroupAssignment, Group> groupFetch = (SingularAttributeJoin<GroupAssignment, Group>) root.fetch(GroupAssignment_.group, JoinType.LEFT);
query.orderBy(cb.asc(groupFetch.get(Group_.title)));

我已将 Fetch 手动转换为 SingularAttributeJoin，之后，我可以使用 get 方法进行排序，但我正在寻找如何无需手动转换 的正确方法。

GroupAssignment 类:

@Entity()
@Table(name = "group_assignment")
public class GroupAssignment {
  @Id
  @Column(name = "group_assignment_id")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

  @ManyToOne
  @JoinColumn(name = "group_id", nullable = false)
  private Group group;

  //other fields, getters and setters
}

GroupAssignment_ 类:

@Generated(value = "org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor")
@StaticMetamodel(GroupAssignment.class)
public abstract class GroupAssignment_ {
  public static volatile SingularAttribute<GroupAssignment, Integer> id;
  public static volatile SingularAttribute<GroupAssignment, Group> group;
}

组类:

@Entity()
@Table(name = "navigation_group")
public class Group {
  @Id
  @Column(name = "group_id")
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Integer id;

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

  //other fields, getters and setters
}

Group_类:

@Generated(value = "org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor")
@StaticMetamodel(Group.class)
public abstract class Group_ {
  public static volatile SingularAttribute<Group, Integer> id;
  public static volatile SingularAttribute<Group, String> title;
}

Answer 1

我认为 javax.persistence.criteria.FetchParent 可以解决您的问题:

FetchParent<GroupAssignment, Group> groupFetch = root.fetch(GroupAssignment_.group, JoinType.LEFT);