@JoinColumn name=cid是什么意思?
//一對多?雙向關聯(lián)
Student.java:
@ManyToOne(cascade?=?{CascadeType.ALL},fetch?=?FetchType.EAGER)
@JoinColumn(name?=?"cid")????///??????
?private?ClassRoom?classRoom;
?
?ClassRoom.java
@Id
@GeneratedValue(generator?=?"cid")
@GenericGenerator(name?=?"cid",strategy?=?"assigned")
@Column(length?=?4)
private?String?cid;?
private?String?cname;?
@OneToMany(cascade?=?CascadeType.ALL,fetch?=?FetchType.LAZY)
@JoinColumn(name?=?"cid")??///?????
private?Set<Student>?stus;請問cid指的是什么 ???? ?這個cid指的是 生成的外鍵字段的名詞 嗎??
有沒有要求必須要與主鍵cid屬性同名?如果沒有要求的換個其他比較好, 都叫cid這樣會有歧義.
還有雙向關聯(lián)雙方實體類?@JoinColumn name="xxx" ? 是都需要寫一樣嗎?
2018-02-24
@JoinColumn(name="rid", referencedColumnName="cid")???? //name=定義外鍵在本表的字段名 referencedColumnName =關聯(lián)外鍵對象的哪個字段
2017-09-13
提問居然亂碼了
ClassRoom :
? ?@Id
? ?@GeneratedValue(generator = "cid")
? ?@GenericGenerator(name = "cid",strategy = "assigned")
? ?@Column(length = 4)
? ?private String cid;?
? ?private String cname;?
? ?@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
? ?@JoinColumn(name = "cid")
? ?private Set<Student> stus;
Student :
? ?@Id
? ?@GeneratedValue?
? ?private int sid;
? ?@Column(length = 25)
? ?private String sname;
? ?private String gender;
? ?private Date birthday;
? ?private String major;
? @ManyToOne(cascade = {CascadeType.ALL},fetch = FetchType.EAGER)
? @JoinColumn(name = "cid")
? ?private ClassRoom classRoom;