Spring-JPA - 如何从自联接表中输出有限的字段

Question

I have an entity named employee which has self join with itself. The join is to represent who is the manager for that employee. When I query the records I am getting the whole hierarchy for the employee.

What I wish to achieve is to fetch only few fields of manager and do not wish to fetch an employee's manager's manager.

I tried doing it using @NamedEntityGraph but not able to get the expected output. Used Projections as well.

I also tried the approach as mentioned here

1. JPA Self Join using JoinTable

2. Self join Spring JPA

- I do not wish to use @Query annotation

@Entity
public class Employee {
    @Id
    @Column(name = "employeeId", nullable = false)
    private String employeeId;

    @Column(name = "firstName", nullable = false)
    private String firstName;

    @Column(name = "lastName", nullable = false)
    private String lastName;

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

    @Column(name = "dateOfJoining", nullable = false)
    private LocalDate dateOfJoining;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "line_manager_id")
    private Employee manager;

}

Actual Result -

{
   "firstName":"Super",
   "lastName":"Manager",
   "middleName":"",
   "dateOfJoining":"2012-12-31",
   "manager":{
      "firstName":"Super",
      "lastName":"Manager",
      "middleName":"",
      "dateOfJoining":"2012-12-31",
      "manager":{
         "firstName":"Admin",
         "lastName":"User",
         "middleName":"",
         "dateOfJoining":"2012-12-31",
         "manager":{
            "firstName":"Admin",
            "lastName":"User",
            "middleName":"",
            "dateOfJoining":"2012-12-31",
            "manager": null,
            "employeeId":"P67"
         },
         "employeeId":"P68"
      },
      "employeeId":"P69"
   },
   "employeeId":"P70"
}

Expected Result

{
   "firstName":"Super",
   "lastName":"Manager",
   "middleName":"",
   "dateOfJoining":"2012-12-31",
   "manager":{
      "firstName":"Super",
      "lastName":"Manager",
      "employeeId":"P69"
   },
   "employeeId":"P70"
}

Answer 1

You should use @JsonIgnore annotation in the fields you do not want to be included. Check here and here for more information.

Answer 2

尝试使用延迟加载

@ManyToOne(fetch=FetchType.LAZY)