@Table(name="USER")
@Entity
public class User {
    private Integer id;
    private String username;
    private String userpassword;
    private String useraddress;
    private List<Order> listOrder;

    @JoinColumn(name="LIST_ORDER")
    @OneToMany(fetch=FetchType.LAZY,cascade=CascadeType.REMOVE)
    public List<Order> getListOrder() {
        return listOrder;
    }
    public void setListOrder(List<Order> listOrder) {
        this.listOrder = listOrder;
    }
    @Id
    @TableGenerator(name="PK_PRIMARY",
    table="order_user_sque",
    pkColumnName="pk_column_name",
    pkColumnValue="pk_column",
    valueColumnName="pk_column_value",
    allocationSize=1)
    @GeneratedValue(strategy=GenerationType.TABLE,generator="PK_PRIMARY")
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }

    @Column(name="USERNAME")
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }

    @Column(name="USERPASSWORD")
    public String getUserpassword() {
        return userpassword;
    }

    public void setUserpassword(String userpassword) {
        this.userpassword = userpassword;
    }

    @Column(name="USERADDRESS")
    public String getUseraddress() {
        return useraddress;
    }
    public void setUseraddress(String useraddress) {
        this.useraddress = useraddress;
    }
}

代碼中：@JoinColumn(name="LIST_ORDER") -> 表示將外鍵名設(shè)置為L(zhǎng)IST_ORDER

@OneToMany(fetch=FetchType.LAZY,cascade=CascadeType.REMOVE) -> OneToMany中fetch表示查詢時(shí)的加載模式[懶加載還是積極加載],cascade屬性表示要級(jí)聯(lián)操作的模式，此處為刪除主表后從表一并刪除。

Order從表代碼

@Entity
@Table(name="ORDER_USER")
public class Order {
    private Integer id;
    private String orderName;
    //private User user;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getOrderName() {
        return orderName;
    }
    public void setOrderName(String orderName) {
        this.orderName = orderName;
    }
}

JPA外鍵關(guān)聯(lián)保存踩坑

比如：用戶表關(guān)聯(lián)了用戶地址的主鍵

在用戶還沒(méi)有設(shè)置地址的時(shí)候能單獨(dú)添加用戶和更新用戶的個(gè)人信息但是當(dāng)用戶添加地址的時(shí)候去更新數(shù)據(jù)的時(shí)候 jpa卻是插入數(shù)據(jù) 而不是更新數(shù)據(jù)、這個(gè)時(shí)候用戶表中的唯一字段則會(huì)報(bào)錯(cuò)、信息已存在！