Question

我在DB中有一个表“seance”（'id'是PK）：

CREATE TABLE seance(
    id int NOT NULL AUTO_INCREMENT,
    seance_id int,
    number int,
    PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

降神

id, seance_id, number
1, 111222, 1951
2, 111222, 1951
3, 111222, 1951
4, 333222, 1415
5, 333222, 1415
6, 333222, 1415

实体类：

@Entity
@Table(name = "seance")
public class Seance {

    public Seance() {}

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "seance_id")
    private Integer seanceId;

    @Column(name = "number")
    @ElementCollection// it is wrong cause require TWO tables
    //what I should write here or modify?
    private Set<Integer> number = new HashSet<Integer>();

    public Seance(Integer seanceId, Set<Integer> number) {
        this.seanceId = seanceId;
        this.number = number;
    }

    // getters and setters

}

因此我希望有一个Seance类的实例：

Integer seanceId：111222;

编号：1951,1951,1951;

Answer 1

是的，它用于处理多个非标准关系映射，ElementCollection可用于定义一对多关系，ElementCollection值始终存储在单独的表中。

Answer 2

你需要拥有这样的实体：

@Entity
@Table(name = "seance")
public class Seance {

    public Seance() {
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "seance_id")
    private Integer seanceId;

@ElementCollection
  @CollectionTable(
        name="NUMBER",
        joinColumns=@JoinColumn(name="OWNER_ID")
  )
    private Set<Integer> number = new HashSet<Integer>();

    public Sessions(Integer seanceId, Set<Integer> number) {
        this.seanceId = seanceId;
        this.number = number;
    }

    public Integer getSeanceId() {
        return seanceId;
    }

    public void setSeanceId(Integer seanceId) {
        this.seanceId = seanceId;
    }

    public Set<Integer> getNumber() {
        return number;`enter code here`
    }

    public void setNumber(Set<Integer> number) {
        this.number = number;
    }

}

这样做，你将有两个表，数字将有一个表，没有和实体。此外，您的概念是事件不好，因为您在使用DataBases进行处理时需要避免冗余。你也可以点这个链接 https://en.wikibooks.org/wiki/Java_Persistence/ElementCollection

Collection <integer>的一对多

2 个答案: