JPA单项一对多外键关联

妖狐艹你老母 2022-05-21 06:44 273阅读 0赞

**`一对多`**即一个对象中包含又另外一个对象的集合。  
`User主表代码`

@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;
        }
    }

代码中:`@JoinColumn(name="LIST_ORDER")` \-> 表示将外键名设置为`LIST_ORDER`  
`@OneToMany(fetch=FetchType.LAZY,cascade=CascadeType.REMOVE)` \-> `OneToMany`中fetch表示查询时的加载模式\[懒加载还是积极加载\],cascade属性表示要级联操作的模式，此处为删除主表后从表一并删除。

`Order从表代码`

@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;
        }
    }