springData表关系：一对一

一、编写两个实体类

1、一对一关系实现：a：使用外键关联　　b：使用主键关联，两个表的主键相同

2、外键方案：配置关联关系：两个实体类互相关联，并且在关联的属性上添加一个@OneToOne代表一个对一个的关系；

　　　　　　　　　　　　　　在属性上添加@JoinColumn　 nme 存储外键的字段名称　　referencedColumnNmae 对方表的字段名称 (可以省略)

3、级联操作：　需要再@OneToOne 注解中添加一个属性 casecade

　　　　　　　CascadeType.PERSIST : 级联添加’　　CascadeType.MEGGE : 级联更新’　　CascadeType.REMOVE : 级联删除’　　CascadeType.ALL : 增删改都用级联操作’

4、主键关联方案：不在使用@JoinColumn注解；使用@PrimaryKeyJoinColumn 注解不需要配置属性；两个实体类关联属性上都要添加

实体类一、@Entity
@Table(name = "cst_customer")
public class Customer {
    // 配置主键自增的策略
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Id
    @Column(name="cust_id")
    private long custId;
    @Column(name="cust_name")
    private String custName;
    @Column(name="cust_source")
    private String custSource;
    @Column(name="cust_indutry")
    private String custIndutry;
    @Column(name="cust_level")
    private String custLevel;
    @Column(name="cust_address")
    private String custAddress;
    @Column(name="cust_phone")
    private String custPhone;

    //表一对一关系
    @OneToOne
    //使用外键关联表
    @JoinColumn(name = "extid",referencedColumnName = "ext_id")
    //使用主键关联表
//    @PrimaryKeyJoinColumn
    private CustomerExt customerExt;

    public CustomerExt getCustomerExt() {
        return customerExt;
    }

    public void setCustomerExt(CustomerExt customerExt) {
        this.customerExt = customerExt;
    }
}实体类二、

@Entity@Table(name = "cst_customer_ext")public class CustomerExt {    @Id    @Column(name="ext_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private long extId;    private String memo;    private  String info;    @OneToOne    @JoinColumn(name="custid",referencedColumnName = "cust_id")    // 主键关联//    @PrimaryKeyJoinColumn    private Customer customer;    public Customer getCustomer() {        return customer;    }    public void setCustomer(Customer customer) {        this.customer = customer;    }}

二、编写dao：两个dao都要继承JpaRepository<CustomerExt,Long>

dao一、
public interface CustomerExtDao extends JpaRepository<CustomerExt,Long> {
}
dao二、
public interface CustomerDao extends JpaRepository<Customer,Long> {
}

三、测试

package cn.zrf.jpa;

import cn.zrf.jpa.dao.CustomerDao;
import cn.zrf.jpa.dao.CustomerExtDao;
import cn.zrf.jpa.entity.Customer;
import cn.zrf.jpa.entity.CustomerExt;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Commit;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")
public class OneToOneTest {
    @Autowired
    private CustomerDao customerDao;
    @Autowired
    private CustomerExtDao customerExtDao;

    @Test
    @Transactional
    @Commit
    public void addCustomer(){
        //  1创建Customer 对象
        Customer customer = new Customer();
        customer.setCustName("张无忌");
        customer.setCustAddress("光明顶");
        customer.setCustLevel("来了老弟");
        //  2创建CustomerExt 对象
        CustomerExt customerExt = new CustomerExt();
        customerExt.setMemo("我是你哥哥");
        customerExt.setInfo("371826");
        //3配置对象之间的关联关系
        customer.setCustomerExt(customerExt);
        customerExt.setCustomer(customer);
        // 4 把对象写入数据路
        customerDao.save(customer);
        customerExtDao.save(customerExt);
    }
}

来源：https://www.cnblogs.com/zhangrongfei/p/11394990.html

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