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Antonio112009
Asked:2020-04-25 05:56:04 +0000 UTC2020-04-25 05:56:04 +0000 UTC

如何使用附加列制作多对多？

  • 772

这个想法很简单：我想创建一个 ManyToMany 依赖项，但有一个额外的列。

在我的项目中，我使用Project Lombok，因此@Data取代了我Getter/Setter/ToString/Equals/Hash.

我的想法 100% 类似于：https ://vladmihalcea.com/the-best-way-to-map-a-many-to-many-association-with-extra-columns-when-using-jpa-and- hibernate/ 但是，这个选项对我不起作用

实体关系图：

在此处输入图像描述

测试程序时出现错误：

Caused by: java.sql.SQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails 
   (`dishdatabase`.`dish_size`, CONSTRAINT `FKqpfda2uojtpf1u243dy0e55fq` FOREIGN KEY (`product_id`) REFERENCES `product` (`id`))

更新 1（2020 年 4 月 25 日）：

项目已移至github：https
://github.com/Antonio112009/Many-To-Many_with_extra_column 底部错误已解决，但出现另一个：我可以将一个对象连接到另一个对象，但无法连接相同的多个对象互相打字。问题和错误在github上进行了描述。

org.springframework.orm.jpa.JpaSystemException: Could not set field value [SHORT_CIRCUIT_INDICATOR] value by reflection : [class com.antonio112009.manyToMany.entity.PostTagId.tagId] 
setter of com.antonio112009.manyToMany.entity.PostTagId.tagId; nested exception is org.hibernate.PropertyAccessException: Could not set field value [SHORT_CIRCUIT_INDICATOR] 
value by reflection : [class com.antonio112009.manyToMany.entity.PostTagId.tagId] setter of com.antonio112009.manyToMany.entity.PostTagId.tagId

下面是我试图在我的项目中实现的代码：

产品.java：

@Entity
@Data
@Table
public class Product {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "product_generator")
    @SequenceGenerator(name="product_generator", sequenceName = "seq_product", allocationSize = 1)
    private Long id;

    @Column
    private String name;

    @OneToMany(
            mappedBy = "product",
            cascade = CascadeType.ALL,
            orphanRemoval = true
    )
    List<DishSize> dishSizes = new ArrayList<>();

    public void addDishSize(DishSize dishSize) {
        dishSizes.add(dishSize);
        dishSize.setProduct(this);
    }

    public void removeDishSize(DishSize dishSize) {
        dishSizes.remove(dishSize);
        dishSize.setProduct(null);
    }
}

DishSize.java

@Entity
@Data
@Table
public class DishSize implements Serializable {

    @Id
    @GeneratedValue
    private Long id;

    private Integer size;

    @ManyToOne(fetch = FetchType.LAZY)
    private Product product;

    @ManyToOne(fetch = FetchType.LAZY)
    private Dish dish;
}

菜.java

@Entity
@Data
@Table
public class Dish {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "dish_generator")
    @SequenceGenerator(name="dish_generator", sequenceName = "seq_dish", allocationSize = 1)
    private Long id;

    @Column
    private String name;

    @OneToMany(
            mappedBy = "dish",
            cascade = CascadeType.ALL,
            orphanRemoval = true
    )
    List<DishSize> dishSizes = new ArrayList<>();

    public void addDishSize(DishSize dishSize) {
        dishSizes.add(dishSize);
        dishSize.setDish(this);
    }

    public void removeDishSize(DishSize dishSize) {
        dishSizes.remove(dishSize);
        dishSize.setDish(null);
    }

测试我的程序是否失败：

DishRepositoryTest.java

@SpringBootTest
class DishRepositoryTest {

    @Autowired
    private DishRepository dishRepository;

    @Autowired
    private ProductRepository productRepository;

    private String name = "Цезарь";

    @BeforeEach
      void setUp() {
        productRepository.deleteAll();
        dishRepository.deleteAll();

        Dish dish = new Dish();
        dish.setName(name);
        dish.setNotes("тест");
        dishRepository.save(dish);
    }

    @Test
    @Transactional
    void deleteProductButNotDish(){

        String nameProduct = "яблоко";
        Integer size = 250;

        Product product = new Product();
        product.setName(nameProduct);
        productRepository.save(product);
        product = productRepository.findByNameAndSort(nameProduct, null);
        Dish dish = dishRepository.findByName(name);

        DishSize dishSize = new DishSize();
        dishSize.setDish(dish);
        dishSize.setSize(size);

        product.addDishSize(dishSize);
        dish.addDishSize(dishSize);
        dishRepository.save(dish);

        //Test
        product = productRepository.findByNameAndSort(nameProduct, null);
        product.getDishSizes().get(0).getDish().removeDishSize(product.getDishSizes().get(0));
        productRepository.save(product);
        productRepository.deleteByNameAndSort(nameProduct, null);

        dish = dishRepository.findByName(name);

        assertNotNull(dish, "checking if dish is not deleted");
        assertNull(productRepository.findByNameAndSort(nameProduct, null), "checking if product is deleted");
        assertEquals(0, dish.getDishSizes().size(), "checking if dishSize is deleted");
    }
}
java

1 个回答

  1. Best Answer

    Github 上的示例

    @ManyToMany c дополнительной колонкой可以在这里找到一个工作示例

    当前，删除其中嵌套了一个或多个对象的对象存在问题。

    更新 1

    删除多个对象的问题几乎解决了。剩下的就是添加对象的级联删除。

    主要要求：

    1. 不要使用@Data 龙目岛。问题出在@EqualsAndHashCode. 可以在此问题中找到有关此事物的来源的链接
    2. equals, addTag/Post,removeTag/Post的写法应与以下示例相同。没有它们，就不可能连接两个实体。

    正确的代码输入

    菜.java

    @Entity
@Getter
@Setter
@Table
public class Dish{

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "dish_generator")
    @SequenceGenerator(name="dish_generator", sequenceName = "seq_dish", allocationSize = 1)
    private Long id;

    @Column
    private String name;

    @OneToMany(
            mappedBy = "dish",
            cascade = CascadeType.ALL,
            orphanRemoval = true
    )
    List<DishSize> dishSizes = new ArrayList<>();

    public void addProduct(Product product, Integer size) {
        DishSize dishSize = new DishSize(product,this,size);
        dishSizes.add(dishSize);
        product.getDishSizes().add(dishSize);
    }

    public void removeProduct(Product product) {
        for (Iterator<DishSize> iterator = dishSizes.iterator(); iterator.hasNext(); ) {
            DishSize dishSize = iterator.next();

            if (dishSize.getDish().equals(this) &&
                    dishSize.getProduct().equals(product)) {
                iterator.remove();
                dishSize.getProduct().getDishSizes().remove(dishSize);
                dishSize.setProduct(null);
                dishSize.setDish(null);
            }
        }
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;

        Dish other = (Dish) obj;
        return id != null && id.equals(other.getId());
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}

    DishSize.java

    @Entity
@Getter
@Setter
@Table
public class DishSize {

    @EmbeddedId
    private DishSizePK id;

    @Column
    private Integer size;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("productId")
    private Product product;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("dishId")
    private Dish dish;

    public DishSize() {}

    public DishSize(Product product, Dish dish, Integer size) {
        this.product = product;
        this.dish = dish;
        this.id = new DishSizePK(product.getId(), dish.getId());
        this.size = size;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;

        if (o == null || getClass() != o.getClass())
            return false;

        DishSize that = (DishSize) o;
        return Objects.equals(product, that.product) &&
                Objects.equals(dish, that.dish);
    }

    @Override
    public int hashCode() {
        return Objects.hash(product, dish);
    }
}

    DishSizePK.java

    @Embeddable
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class DishSizePK implements Serializable {

    @Column
    private Long productId;

    @Column
    private Long dishId;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;

        if (o == null || getClass() != o.getClass())
            return false;

        DishSizePK that = (DishSizePK) o;
        return Objects.equals(productId, that.productId) &&
                Objects.equals(dishId, that.dishId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(productId, dishId);
    }
}

    产品

    @Entity
@Getter
@Setter
@ToString
@Table
public class Product{

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "product_generator")
    @SequenceGenerator(name="product_generator", sequenceName = "seq_product", allocationSize = 1)
    private Long id;

    @Column
    private String name;

    @OneToMany(
            mappedBy = "product",
            cascade = CascadeType.ALL,
            orphanRemoval = true
    )
    List<DishSize> dishSizes = new ArrayList<>();

    public void addDish(Dish dish, Integer size) {
        DishSize dishSize = new DishSize(this,dish,size);
        dishSizes.add(dishSize);
        dish.getDishSizes().add(dishSize);
    }

    public void removeDish(Dish dish) {
        for (Iterator<DishSize> iterator = dishSizes.iterator(); iterator.hasNext(); ) {
            DishSize dishSize = iterator.next();

            if (dishSize.getProduct().equals(this) &&
                    dishSize.getDish().equals(dish)) {
                iterator.remove();
                dishSize.getDish().getDishSizes().remove(dishSize);
                dishSize.setProduct(null);
                dishSize.setDish(null);
            }
        }
    }

    @Override
    public boolean equals(Object obj) {

        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;

        Product other = (Product) obj;
        return id != null && id.equals(other.getId());
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}
    • 0

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