java - 当数据库中有多个对象时，Spring boot rest 响应在 OneToMany 上给出 1 个结果

Question

对于一个学校项目，我们必须制作一个与我们的 MySQL 数据库通信的 spring boot rest 服务器。这是数据库的屏幕截图:

对于我的用户模型，我有以下内容:

@Entity
@Table(name = "User")
@Setter
public class User extends ResourceSupport implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id_user", updatable = false, nullable = false)
    @JsonSerialize
    private Long id;
    @Getter
    private String firstName;
    @Getter
    private String lastName;
    @Getter
    private String email;
    @Getter
    private String password;
    @Getter
    private Double hourlyWage;
    @Getter
    private String adress;
    @Getter
    private String city;
    @Getter
    private Boolean isManager;
    @Getter
    @OneToMany
    @JoinTable(name = "user_to_project", joinColumns = @JoinColumn(name = "id"), inverseJoinColumns = @JoinColumn(name = "project_id"))
    private List<Project> projects;

然后对于我的项目类:

@Entity
@Table(name = "project")
@Setter
public class Project extends ResourceSupport {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id_project")
    @JsonSerialize
    private Long id;
    @Getter
    @OneToOne
    @JoinColumn(name = "owner", referencedColumnName = "id")
    private Company owner;
    @Getter
    private String description;
    @Getter
    private String name;
    @Getter
    private double payout;
    @Getter
    private boolean internal;
    @Getter
    @OneToMany
    @JoinTable(name = "user_to_project", joinColumns = @JoinColumn(name = "id"), inverseJoinColumns = @JoinColumn(name = "user_id"))
    private List<User> users;

我不知道我做错了什么，因为这是我得到的结果:

当我的链接表中有这个时:

我希望有人能回答我的问题，因为我已经厌倦了 spring boot 和这个学校项目。

Answer 1

我不知道它是否对你有帮助，但下面是我的代码:

// Role
@LazyCollection(LazyCollectionOption.FALSE)
@ManyToMany(mappedBy = "roles")
@JsonIgnoreProperties("roles")
@OrderBy("id")
private List<User> users;

// User
@LazyCollection(LazyCollectionOption.FALSE)
@ManyToMany
@JoinTable(name = "users_roles",
        joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id")
)
@JsonIgnoreProperties("users")
@OrderBy("id")
private List<Role> roles;

另外，请注意 - 在 JPA 中，一个表是“主”(在我的示例中是用户)，另一个是“从”，而不是 m2m 表相等的 SQL。 "Slave"应该在 @ManyToMany 注释中有修饰符 mappedBy。

表 DDL(postgres):

create table roles
(
  id               serial                not null
    constraint roles_pkey
    primary key,
  version          bigint default 0
);

create table users
(
  id               serial                not null
    constraint users_pkey
    primary key,
  version          bigint  default 0
);

create table users_roles
(
  user_id integer not null
    constraint fk_users
    references users,
  role_id integer not null
    constraint fk_roles
    references roles,
  constraint users_roles_pkey
  primary key (user_id, role_id)
);

希望对您有所帮助。祝你好运。