Spring Boot JPA @OneToOne

本文介绍 Spring Boot JPA @OneToOne 的使用方法。

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目录

• 开发环境
• 基础示例

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开发环境

• JDK 8
• MySQL 8

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基础示例

1. 创建数据表。

CREATE SCHEMA `test` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;

USE `test`;

CREATE TABLE `student` (
  `id`        BIGINT     UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '主键',
  `number`    CHAR(10)            NOT NULL                COMMENT '学号',
  `name`      VARCHAR(30)         NOT NULL                COMMENT '姓名',
  `family_id` TINYINT    UNSIGNED NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE INDEX `id_UNIQUE` (`id` ASC) VISIBLE,
  UNIQUE INDEX `number_UNIQUE` (`number` ASC) VISIBLE)
COMMENT = '学生表';

CREATE TABLE `family` (
  `id`     BIGINT      UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '主键',
  `father` VARCHAR(30)          NOT NULL                COMMENT '父亲姓名',
  `mother` VARCHAR(30)          NOT NULL                COMMENT '母亲姓名',
  PRIMARY KEY (`id`),
  UNIQUE INDEX `id_UNIQUE` (`id` ASC) VISIBLE);

2. 如何创建 Spring Boot JPA 工程请参考：https://www.jianshu.com/p/e2b64d5c6107

3. 创建 PO（Persistence Object） 对象。

package tutorial.spring.boot.domain;

import javax.persistence.*;

@Entity
@Table(name = "family")
public class FamilyPO {

    /**
     * 自增主键
     */
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String father;

    private String mother;

    // Getter、Setter、toString 方法略
}

package tutorial.spring.boot.domain;

import javax.persistence.*;

@Entity
@Table(name = "student")
public class StudentPO {

    /**
     * 自增主键
     */
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    /**
     * 学号
     */
    private String number;

    /**
     * 姓名
     */
    private String name;

    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "family_id")
    private FamilyPO family;

    // Getter、Setter、toString 方法略
}

注意：@JoinColumn(name = "family_id") 可以省略。

4. 创建继承 JpaRepository 的 Repository 接口类。

package tutorial.spring.boot.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import tutorial.spring.boot.domain.FamilyPO;

@Repository
public interface FamilyRepository extends JpaRepository<FamilyPO, Long> {
}

package tutorial.spring.boot.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import tutorial.spring.boot.domain.StudentPO;

@Repository
public interface StudentRepository extends JpaRepository<StudentPO, Long> {
}

5. 编写单元测试。

package tutorial.spring.boot.dao;

import org.apache.commons.lang3.RandomStringUtils;
import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.MethodOrderer;
import org.junit.jupiter.api.Order;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestMethodOrder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import tutorial.spring.boot.domain.FamilyPO;
import tutorial.spring.boot.domain.StudentPO;

import java.util.List;
import java.util.Objects;

@SpringBootTest
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
class StudentRepositoryTest {

    @Autowired
    private FamilyRepository familyRepository;

    @Autowired
    private StudentRepository studentRepository;

    /**
     * 测试 [CascadeType.ALL] 条件下的级联新增
     */
    @Test
    @Order(1)
    void testInsert() {
        // family 和 student 表中都没有记录
        Assertions.assertThat(familyRepository.count()).isEqualTo(0);
        Assertions.assertThat(studentRepository.count()).isEqualTo(0);
        // 创建 family 和 student 实体对象并将其绑定起来
        StudentPO student = new StudentPO();
        student.setNumber(RandomStringUtils.randomAlphanumeric(10));
        student.setName(RandomStringUtils.randomAlphanumeric(2, 20));
        FamilyPO family = new FamilyPO();
        family.setFather(RandomStringUtils.randomAlphanumeric(2, 20));
        family.setMother(RandomStringUtils.randomAlphanumeric(2, 20));
        student.setFamily(family);
        // 执行保存 student 实体对象的操作
        studentRepository.save(student);
        // family 和 student 表中各新增一条记录，且新增记录信息与保存的 student 实体对象信息一致
        List<FamilyPO> families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(1);
        List<StudentPO> students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        Assertions.assertThat(students.get(0).getNumber()).isEqualTo(student.getNumber());
        Assertions.assertThat(students.get(0).getName()).isEqualTo(student.getName());
        Assertions.assertThat(students.get(0).getFamily().getFather()).isEqualTo(families.get(0).getFather());
        Assertions.assertThat(students.get(0).getFamily().getMother()).isEqualTo(families.get(0).getMother());
        Assertions.assertThat(students.get(0).getFamily().getId()).isEqualTo(families.get(0).getId());
    }

    /**
     * 测试 [CascadeType.ALL] 条件下的级联更新
     * 只更新级联关系被持有方属性
     */
    @Test
    @Order(2)
    void testUpdate1() {
        // 依赖于之前的单元测试，此时 student 和 family 表中应各有一条记录
        List<FamilyPO> families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(1);
        List<StudentPO> students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        StudentPO student = students.get(0);
        FamilyPO family = families.get(0);
        // 修改 student 信息及关联的 family 信息后保存
        String originalStudentNumber = student.getNumber();
        student.setNumber(originalStudentNumber.substring(1));
        String originalStudentName = student.getName();
        student.setName(originalStudentName + RandomStringUtils.randomAlphabetic(1));
        student.getFamily().setFather(student.getFamily().getFather() + RandomStringUtils.randomAlphabetic(1));
        student.getFamily().setMother(student.getFamily().getMother() + RandomStringUtils.randomAlphabetic(2));
        studentRepository.save(student);
        // 保存后 student 和 family 表中还应只有一条记录
        families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(1);
        students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        // 校验 student 及关联的 family 信息已更新且与原来不同
        FamilyPO findFamilyResult = families.get(0);
        StudentPO findStudentResult = students.get(0);
        Assertions.assertThat(findStudentResult.getNumber())
                .isEqualTo(student.getNumber())
                .isNotEqualTo(originalStudentNumber);
        Assertions.assertThat(findStudentResult.getName())
                .isEqualTo(student.getName())
                .isNotEqualTo(originalStudentName);
        Assertions.assertThat(findStudentResult.getFamily().getFather())
                .isEqualTo(student.getFamily().getFather())
                .isEqualTo(findFamilyResult.getFather())
                .isNotEqualTo(family.getFather());
        Assertions.assertThat(findStudentResult.getFamily().getMother())
                .isEqualTo(student.getFamily().getMother())
                .isEqualTo(findFamilyResult.getMother())
                .isNotEqualTo(family.getMother());
    }

    /**
     * 测试 [CascadeType.ALL] 条件下的级联更新
     * 重新绑定级联关系被持有方
     */
    @Test
    @Order(3)
    void testUpdate2() {
        // 依赖于之前的单元测试，此时 student 和 family 表中应各有一条记录
        List<FamilyPO> families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(1);
        List<StudentPO> students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        StudentPO student = students.get(0);
        FamilyPO family = families.get(0);
        // 为 student 重新绑定 family 并保存
        FamilyPO newFamily = new FamilyPO();
        newFamily.setFather(family.getFather() + RandomStringUtils.randomAlphabetic(2));
        newFamily.setMother(family.getMother() + RandomStringUtils.randomAlphabetic(1));
        student.setFamily(newFamily);
        studentRepository.save(student);
        // family 表应该保留之前绑定的 family 信息并新增新绑定的 family 信息
        families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(2);
        students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        StudentPO findStudentResult = students.get(0);
        FamilyPO findOldFamilyResult;
        FamilyPO findNewFamilyResult;
        if (Objects.equals(families.get(0).getId(), findStudentResult.getFamily().getId())) {
            findNewFamilyResult = families.get(0);
            findOldFamilyResult = families.get(1);
        } else {
            findNewFamilyResult = families.get(1);
            findOldFamilyResult = families.get(0);
        }
        Assertions.assertThat(findOldFamilyResult.getId()).isEqualTo(family.getId());
        Assertions.assertThat(findOldFamilyResult.getFather()).isEqualTo(family.getFather());
        Assertions.assertThat(findOldFamilyResult.getMother()).isEqualTo(family.getMother());
        Assertions.assertThat(findNewFamilyResult.getId()).isEqualTo(findStudentResult.getFamily().getId());
        Assertions.assertThat(findNewFamilyResult.getFather()).isEqualTo(findStudentResult.getFamily().getFather());
        Assertions.assertThat(findNewFamilyResult.getMother()).isEqualTo(findStudentResult.getFamily().getMother());
    }

    @Test
    @Order(4)
    void testDelete() {
        // 依赖于之前的单元测试，此时 student 表中应有一条记录，family 表中应有两条记录
        List<FamilyPO> families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(2);
        List<StudentPO> students = studentRepository.findAll();
        Assertions.assertThat(students.size()).isEqualTo(1);
        FamilyPO familyNoUsed;
        if (Objects.equals(families.get(0).getId(), students.get(0).getFamily().getId())) {
            familyNoUsed = families.get(1);
        } else {
            familyNoUsed = families.get(0);
        }
        // 执行删除 student 操作
        studentRepository.delete(students.get(0));
        Assertions.assertThat(studentRepository.count()).isEqualTo(0);
        families = familyRepository.findAll();
        Assertions.assertThat(families.size()).isEqualTo(1);
        Assertions.assertThat(families.get(0).getId()).isEqualTo(familyNoUsed.getId());
        Assertions.assertThat(families.get(0).getFather()).isEqualTo(familyNoUsed.getFather());
        Assertions.assertThat(families.get(0).getMother()).isEqualTo(familyNoUsed.getMother());
    }
}

说明：
因为使用了 CascadeType.ALL，级联关系持有方拥有被持有方的所有权限，本例中 StudentPO 是级联关系持有方，FamilyPO 是级联关系的被持有方，因此 StudentPO 拥有 FamilyPO 的所有权限，测试用例中创建的两个 PO 对象本来都不存在于数据库中，因为 StudentPO 拥有 FamilyPO 的所有权限，所以保存 StudentPO 实例时也同时保存了 FamilyPO 实例，有关级联更新和删除详情请参考测试用例。