Hibernate Fetch不再是Join的子类型

Question

我正在使用带有动态条件的Hibernate 5.2.10，并发现Fetch不再可以分配给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)));

我已经手动将Fetch转换为SingularAttributeJoin，之后，我可以使用get方法进行排序，但我正在寻找正确的方法， 如果不手动编译我怎么做。

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;
}

小组课程：

@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);

Answer 2

看来正确的方法是下一个：

query.orderBy(cb.asc(root.get(GroupAssignment_.group).get(Group_.title)));

因此，使用多次调用.get方法，您可以根据需要尽可能深入。