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首页 > 解决方案 > JPA。双向关联：ManyToOne。删除父级时如何删除关联？

spring-boot - JPA。双向关联：ManyToOne。删除父级时如何删除关联？

问题描述

我有两个实体：Product和Category

  public class Category {
    @Id
    @GeneratedValue(generator = "inc")
    @GenericGenerator(name = "inc", strategy = "increment")
    private int id;

    @OneToMany(cascade =  CascadeType.PERSIST, mappedBy = "category")
    private Set<Product> products;
}

public class Product {
    @Id
    @GeneratedValue(generator = "inc")
    @GenericGenerator(name = "inc", strategy = "increment")
    private int id;

    @ManyToOne
    @JoinColumn(name = "categories_id")
    private Category category;
}

在删除父级（类别）后，我想将我的子级（产品）保留在 db 中（值category等于null）。目前，当我尝试删除一个类别时，我收到此错误：

org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException: Referential integrity constraint violation: "CONSTRAINT_F2: PUBLIC.PRODUCTS FOREIGN KEY(CATEGORIES_ID) REFERENCES PUBLIC.CATEGORIES(ID)

标签： spring-bootspring-data-jpaforeign-keyssql-delete

解决方案

在删除类别之前，您需要更新关联。例如：

Category category = ...
for (Product p : category.getProducts()) {
   p.setCategory(null);
}
category.getProducts().clear();
entityManager.remove(category);

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