hibernate基于实体类注解实现一对多的配置

灰太狼 2024-02-18 21:22 10阅读 0赞

一的一方：

@Entity
    @Table(name = "user")
    public class User {
        private  Long id;
        private  String name;
        private  String address;
        private  Integer age;
        private Date createTime;
        private  Date updateTime;
        private Set<UserOrder> listOrder;
    
        @OneToMany(mappedBy = "user", cascade = CascadeType.ALL)//mappedBy = "user"是设置关系由多的一方维护，cascade为级联操作
        public Set<UserOrder> getListOrder() {
            return listOrder;
        }
    
        public void setListOrder(Set<UserOrder> listOrder) {
            this.listOrder = listOrder;
        }
    
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)//主键生成策略
        public Long getId() {
            return id;
        }
     
        public void setId(Long id) {
            this.id = id;
        }
        
        @Column(nullable = false,name = "name",length = 50)
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
        
        @Column(nullable = false,name = "address")
        public String getAddress() {
            return address;
        }
    
        public void setAddress(String address) {
            this.address = address;
        }
        
        @Column(nullable = false,name = "age",length = 3)
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
        
        @Temporal(TemporalType.TIMESTAMP)
        @Column(updatable = false)
        @org.hibernate.annotations.CreationTimestamp
        public Date getCreateTime() {
            return createTime;
        }
    
        public void setCreateTime(Date createTime) {
            this.createTime = createTime;
        }
        
        @Temporal(TemporalType.TIMESTAMP)
        @Column(updatable = true)
        @org.hibernate.annotations.CreationTimestamp
        public Date getUpdateTime() {
            return updateTime;
        }
    
        public void setUpdateTime(Date updateTime) {
            this.updateTime = updateTime;
        }
    
        public User() {
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", address='" + address + '\'' +
                    ", age=" + age +
                    ", createTime=" + createTime +
                    ", updateTime=" + updateTime +
                    ", listOrder=" + listOrder +
                    '}

多的一方：

@Entity
    @Table(name = "t_order")//对应的表的名字
    public class UserOrder {
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        private long id;
    
        @ManyToOne(cascade = {CascadeType.ALL})
        @JoinColumn(name = "user_id")//user_id为t_order表中的user_id字段名（hibernate会自动帮我们生成外键）
        private User user;
    
        @Column(name = "order_name")//如果不设置name参数则默认表里的字段名与实体类的属性名一致，如果表的字段名与实体类属性不一致则name参数的值就就是表里面对应的字段名
        private String orderName;
    
        @Column(name = "create_date")
        private Date createDate;
    
        public long getId() {
            return id;
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        public User getUser() {
            return user;
        }
    
        public void setUser(User user) {
            this.user = user;
        }
    
        public String getOrderName() {
            return orderName;
        }
    
        public void setOrderName(String orderName) {
            this.orderName = orderName;
        }
    
        public Date getCreateDate() {
            return createDate;
        }
    
        public void setCreateDate(Date createDate) {
            this.createDate = createDate;
        }
    
        @Override
        public String toString() {
            return "UserOrder{" +
                    "id=" + id +
                    ", orderName='" + orderName + '\'' +
                    ", createDate=" + createDate +
                    '}';
        }
    }

配置文件applicationContext.xml：

<bean id="sessionFactory" name="sf" class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="packagesToScan" value="com.mysql.entity"/>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">${hibernate.dialect}</prop>
                <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
                <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop>
                <prop key="hibernate.jdbc.batch_size">${hibernate.jdbc.batch_size}</prop>
                <prop key="hibernate.enable_lazy_load_no_trans">${hibernate.enable_lazy_load_no_trans}</prop>
            </props>
    
        </property>
    </bean>

在实体类使用注解的方式配置关系就不需要再创建hibernate的映射文件了

建表或者建立字段的时候一定要细心，有好几次都是表名或者字段名是关键字，导致程序运行的时候报了语法错误，找了好久才发现是这个问题，所以在这里记录一下这个坑，以免以后再犯。