Spring Data JPA-多雙向@ManyToOne傳播數據

Question

    @Entity
    @Getter
    @Setter
    @NoArgsConstructor
    @ToString 
    public class Lawyer extends ID{
        @EqualsAndHashCode.Exclude
        @ToString.Exclude
        @JsonIgnore
        @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "lawyer")
        private Set<Appointment> appointments = new HashSet<>();

public void addAppointment(Client client, LocalDateTime data) {
            Appointment app = new Appointment (client,this,data);
            this.consultas.add(app);
            app.getClient().getAppointments().add(app);
        }

       }

        @Entity
        @Getter
        @Setter
        @NoArgsConstructor
        @ToString
        public class Appointment extends ID{

            @EqualsAndHashCode.Exclude
            @ToString.Exclude
            @ManyToOne
            private Client client;

            @EqualsAndHashCode.Exclude
            @ToString.Exclude
            @ManyToOne
            private Lawyer lawyer;
        }



        @Entity
        @Getter
        @Setter
        @NoArgsConstructor
        @ToString
        public class Client extends ID{

            @EqualsAndHashCode.Exclude
            @ToString.Exclude
            @JsonIgnore
            @OneToMany
            private Set<Appointment> appointments = new HashSet<>();
        }

        @MappedSuperclass
        @Getter
        @Setter
        @NoArgsConstructor
        public class ID{
            @Id
            @GeneratedValue(strategy = GenerationType.IDENTITY)
            private Long id;
        }

BootStrap類

@Component
public class Bootstrap implements ApplicationListener<ContextRefreshedEvent> {
    private LaywerRepoI LaywerService;

    public Bootstrap(LaywerRepoI LaywerService) {
        this.LaywerService = LaywerService;
    }

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        Client c1 = new Client("Lukz", LocalDate.of(1971, 11, 26));
        Client c2 = new Client("Adrian", LocalDate.of(1956, 01, 28));
        Client c3 = new Client("Danny", LocalDate.of(1936, 1, 11));

        Laywer l1 = new Laywer("Morgan", LocalDate.of(1941, 1, 1));
        Laywer l2 = new Laywer("Ana", LocalDate.of(1931, 10, 1));

        l1.addAppointment(c1,LocalDateTime.of(2018, 11, 22,18, 25));
        l1.addAppointment(c1,LocalDateTime.of(2018, 11, 22, 10, 15));

        LawyerService.save(l1);
        LawyerService.save(l2);
    }
}

當我在班級律師上進行新的約會時，我試圖將數據從律師傳播到客戶，但是我只能將其傳達給約會。 從約會到客戶端，我無法傳播它。...我收到此錯誤：

原因：java.lang.IllegalStateException：org.hibernate.TransientPropertyValueException：對象引用了一個未保存的瞬態實例-在刷新之前保存該瞬態實例

如何從約會傳播到客戶？ 我已經閱讀了一些有關此類案例的文章，但我仍然不理解它們。

Answer 1

保存Lowyer ，因此需要層疊Lowyer->約會和約會->客戶關系。

因此，您還必須級聯關系“ 約會->客戶” 。

        @Entity
        @Getter
        @Setter
        @NoArgsConstructor
        @ToString
        public class Appointment extends ID{

            @EqualsAndHashCode.Exclude
            @ToString.Exclude
            @ManyToOne(cascade = CascadeType.ALL)
            private Client client;

            @EqualsAndHashCode.Exclude
            @ToString.Exclude
            @ManyToOne
            private Lawyer lawyer;
        }

Answer 2

spring-data-jpa是JPA之上的一層。 每個實體都有其自己的存儲庫，您必須處理該存儲庫。

@Entity
public class Lawyer  {
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = "client", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Appointment> appointments;

@Entity
public class Client {
    @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = "lawyer", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Appointment> appointments;

@Entity
public class Appointment {
    @EmbeddedId
    private AppointmentId id = new AppointmentId();

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("lawyerId")
    private Lawyer lawyer;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("clientId")
    private Client client;

    public Appointment() {}
    public Appointment(Lawyer lawyer, Client client) {
        this.lawyer = lawyer;
        this.client = client;
    }

@SuppressWarnings("serial")
@Embeddable
public class AppointmentId implements Serializable {
    private Long lawyerId;
    private Long clientId;

並使用它，如上所示：

@Transactional
private void update() {
    System.out.println("Step 1");
    Client client1 = new Client();
    Lawyer lawyer1 = new Lawyer();
    Appointment apt1 = new Appointment(lawyer1, client1);
    clientRepo.save(client1);
    lawyerRepo.save(lawyer1);
    appointmentRepo.save(apt1);

    System.out.println("Step 2");
    Client client2 = new Client();
    Lawyer lawyer2 = new Lawyer();
    Appointment apt2 = new Appointment(lawyer2, client2);
    lawyerRepo.save(lawyer2);
    clientRepo.save(client2);
    appointmentRepo.save(apt2);

    System.out.println("Step 3");
    client2 = clientRepo.getOneWithLawyers(2L);
    client2.getAppointments().add(new Appointment(lawyer1, client2));
    clientRepo.save(client2);

    System.out.println("Step 4 -- better");
    Appointment apt3 = new Appointment(lawyer2, client1);
    appointmentRepo.save(apt3);
}

注意，我沒有顯式設置AppointmentId id。 這些由持久層（在這種情況下為休眠）處理。

還請注意，由於設置了CascadeType.ALL ，您可以使用其自己的存儲庫來顯式更新Appointment條目，也可以通過將其添加到列表中並將其從列表中刪除來進行更新，如圖所示。 將CascadeType.ALL用於spring-data-jpa的問題在於，即使您預取了聯接表實體，spring-data-jpa仍將再次執行此操作。 嘗試通過CascadeType.ALL為新實體更新關系是有問題的。

如果沒有CascadeType則lawyers或Clients列表（應為Sets）都不是關系的所有者，因此，在持久性方面添加到他們將不會完成任何事情，並且僅用於查詢結果。

在閱讀Appointment關系時，由於沒有FetchType.EAGER需要專門獲取它們。 FetchType.EAGER的問題是開銷，如果您不希望加入連接，並且同時將其放在“ Client和“ Lawyer那么您將創建一個遞歸提取，以獲取所有Clients和lawyers的任何查詢。

@Query("select c from Client c left outer join fetch c.lawyers ls left outer join fetch ls.lawyer where t.id = :id")
Client getOneWithLawyers(@Param("id") Long id);

最后，請始終檢查日志。 創建關聯需要spring-data-jpa（我認為是JPA）讀取現有表以查看該關系是新關系還是更新關系。 無論您自己創建和保存Appointment還是預取列表，都會發生這種情況。 JPA有單獨的合並，我認為您可以更有效地使用它。

create table appointment (client_id bigint not null, lawyer_id bigint not null, primary key (client_id, lawyer_id))
create table client (id bigint generated by default as identity, primary key (id))
alter table appointment add constraint FK3gbqcfd3mnwwcit63lybpqcf8 foreign key (client_id) references client
create table lawyer (id bigint generated by default as identity, primary key (id))
alter table appointment add constraint FKc8o8ake38y74iqk2jqpc2sfid foreign key (lawyer_id) references lawyer

insert into client (id) values (null)
insert into lawyer (id) values (null)
select appointmen0_.client_id as client_i1_0_0_, appointmen0_.lawyer_id as lawyer_i2_0_0_ from appointment appointmen0_ where appointmen0_.client_id=? and appointmen0_.lawyer_id=?
insert into appointment (client_id, lawyer_id) values (?, ?)

insert into lawyer (id) values (null)
insert into client (id) values (null)
select appointmen0_.client_id as client_i1_0_0_, appointmen0_.lawyer_id as lawyer_i2_0_0_ from appointment appointmen0_ where appointmen0_.client_id=? and appointmen0_.lawyer_id=?
insert into appointment (client_id, lawyer_id) values (?, ?)

select client0_.id as id1_1_0_, appointmen1_.client_id as client_i1_0_1_, appointmen1_.lawyer_id as lawyer_i2_0_1_, lawyer2_.id as id1_2_2_, appointmen1_.lawyer_id as lawyer_i2_0_0__, appointmen1_.client_id as client_i1_0_0__ from client client0_ left outer join appointment appointmen1_ on client0_.id=appointmen1_.lawyer_id left outer join lawyer lawyer2_ on appointmen1_.lawyer_id=lawyer2_.id where client0_.id=?
select client0_.id as id1_1_1_, appointmen1_.lawyer_id as lawyer_i2_0_3_, appointmen1_.client_id as client_i1_0_3_, appointmen1_.client_id as client_i1_0_0_, appointmen1_.lawyer_id as lawyer_i2_0_0_ from client client0_ left outer join appointment appointmen1_ on client0_.id=appointmen1_.lawyer_id where client0_.id=?
select appointmen0_.client_id as client_i1_0_0_, appointmen0_.lawyer_id as lawyer_i2_0_0_ from appointment appointmen0_ where appointmen0_.client_id=? and appointmen0_.lawyer_id=?
insert into appointment (client_id, lawyer_id) values (?, ?)

select appointmen0_.client_id as client_i1_0_0_, appointmen0_.lawyer_id as lawyer_i2_0_0_ from appointment appointmen0_ where appointmen0_.client_id=? and appointmen0_.lawyer_id=?
insert into appointment (client_id, lawyer_id) values (?, ?)