我没有在春季启动时自动保存

Question

我正在使用 JPA 创建一个简单的春季启动程序，以显示学生和电话号码关系。

CODE

学生实体

package student.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    Long id;
    String name;
    int roll;
    @OneToOne
    PhoneNumber num;

    public Student() {
        super();
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getRoll() {
        return roll;
    }

    public PhoneNumber getNum() {
        return num;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setRoll(int roll) {
        this.roll = roll;
    }

    public void setNum(PhoneNumber num) {
        this.num = num;
    }

}

电话号码实体

package student.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
@Entity
public class PhoneNumber {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    Long id;
    String num;
    String type;
    @OneToOne
    Student stu;

    public PhoneNumber() {
        super();
    }



    public PhoneNumber(String num, String type) {
        super();
        this.num = num;
        this.type = type;
    }



    public Long getId() {
        return id;
    }
    public String getNum() {
        return num;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public void setNum(String num) {
        this.num = num;
    }

    public Student getStu() {
        return stu;
    }

    public void setStu(Student stu) {
        this.stu = stu;
    }



}

学生和电话号码回购

package student.repo;

import org.springframework.data.repository.CrudRepository;

import student.entity.Student;

public interface StudentRepo extends CrudRepository<Student, Long> {

}

package student.repo;

import org.springframework.data.repository.CrudRepository;

import student.entity.PhoneNumber;

public interface PhoneNumberRepo extends CrudRepository<PhoneNumber, Long>{

}

SeedFile输入虚拟数据

package student;

import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

import student.entity.PhoneNumber;
import student.entity.Student;
import student.repo.PhoneNumberRepo;
import student.repo.StudentRepo;

@Component
public class SeedDb implements CommandLineRunner {
    private StudentRepo studentRepo;
    private PhoneNumberRepo phoneNumberRepo;

    public SeedDb(StudentRepo studentRepo, PhoneNumberRepo phoneNumberRepo) {
        super();
        this.studentRepo = studentRepo;
        this.phoneNumberRepo = phoneNumberRepo;
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println("######################");
        Student stu1 = new Student();
        stu1.setName("X");
        stu1.setRoll(4);
        PhoneNumber p = new PhoneNumber("9090909090","Home");
        phoneNumberRepo.save(p); //saving phone number to database
        stu1.setNum(p);
        studentRepo.save(stu1);

    }

}

在此程序中（在seedDb文件中），我必须先使用 phoneNumberRepo 手动保存电话号码，然后再将其设置为学生，有在线教程，不需要这一步。

此外，学生的ID不会保存到电话号码，如屏幕截图

所示

请告诉我如何将 PhoneNumber 设置为学生而不将其保存到数据库，即当我保存学生时， phoneNumber < / strong>自动保存到数据库以及如何自动将学生的ID设置为电话号码。

Answer 1

您的代码中的问题是您在学生中设置了PhoneNumber，但您从未在您的PhoneNumber中设置学生。

对于双向关系，您需要在您创建关系的两个实体之一的cascade注释中使用@OneToOne参数。拇指的规则是，应该从父母到孩子进行级联。在您的情况下，Student是父类，因此您应该执行以下操作：

@OneToOne(cascade = CascadeType.ALL)
PhoneNumber num;

创建一个像这样的学生：

Student student = new Student();
student.setName("John Doe");
student.setRoll(4);
PhoneNumber phoneNumber = new PhoneNumber("9090909090", "Home");
student.setNum(phoneNumber);
phoneNumber.setStu(student);
studentRepository.save(student);

结果：