java - Spring Boot JPA - ManyToOne关系导致额外的sql

Question

我有 3 个具有简单关系的对象，如下所示:

大学:

@Entity
public class University {

  @Id
  @GeneratedValue
  private Long id;

  private String name;

}

师资队伍:

@Entity
public class Faculty {

  @Id
  @GeneratedValue
  private Long id;

  private String name;

  @Column(name = "university_id", nullable = false)
  private Long universityId;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinFetch(value = JoinFetchType.OUTER)
  @JoinColumn(name = "university_id", insertable = false, updatable = false, nullable = false)
  private University university;
}

专长:

@Entity
public class Specialty {

  @Id
  @GeneratedValue
  private Long id;

  private String name;

  @Column(name = "faculty_id", nullable = false)
  private Long facultyId;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinFetch(value = JoinFetchType.OUTER)
  @JoinColumn(name = "faculty_id", insertable = false, updatable = false, nullable = false)
  private Faculty faculty;
}

我正在使用 EclipseLink 和 Spring CrudRepository 来操作这些实体。 当我打电话时

specialtyRepository.findAll();

我得到了sql

SELECT * FROM specialty LEFT OUTER JOIN faculty ON (faculty.ID = specialty.faculty_id) ...

以及额外的sql，例如

SELECT * FROM university WHERE ((ID = ?)) ...

我想阻止这个sql请求；

有人可以告诉我如何解决这个问题吗？ 谢谢您的任何提示

Answer 1

对于 @ManyToOne 中的延迟加载，我必须在 EclipseLink 中启用动态编织: http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Advanced_JPA_Development/Performance/Weaving

我通过继承解决了这个问题； 我创建了没有关系的基础实例；

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class FacultyBase {

  @Id
  @GeneratedValue
  private Long id;

  private String name;

  @Column(name = "university_id", nullable = false)
  private Long universityId;

}

以及具有关系的实例

@Entity
public class Faculty extends Faculty {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "university_id", insertable = false, updatable = false, nullable = false)
    private University university;

}

因此，在专业实例中，我使用FacultyBase而不是Faculty