java - 无法使用复合键在 Jpa 中插入实体
问题描述
我有一种情况,我想将数据插入到具有主键作为复合键的表中,并且复合键的每个部分都是多对一关系。现在,当我尝试插入一个元素时,我收到一条错误消息,指出该字段应该具有默认值。请看下面。
@Entity
@Table(name = "products")
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="id")
private long id;
}
@Entity
@Table(name = "product_categories")
public class ProductCategory {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="id")
private long id;
}
@Entity
@Table(name = "product_2_product_categories")
public class ProductToProductCategories {
@EmbeddedId
private ProductToProductCategoryId productToProductCategoryId;
public ProductToProductCategories(){}
public ProductToProductCategories(ProductToProductCategoryId productToProductCategoryId) {
this.productToProductCategoryId = productToProductCategoryId;
}
public ProductToProductCategoryId getProductToProductCategoryId() {
return productToProductCategoryId;
}
public void setProductToProductCategoryId(ProductToProductCategoryId productToProductCategoryId) {
this.productToProductCategoryId = productToProductCategoryId;
}
}
@Embeddable
public class ProductToProductCategoryId implements Serializable {
@ManyToOne
@JoinColumn(name = "productId", referencedColumnName = "id")
private Product productId;
@ManyToOne
@JoinColumn(name = "productCategoryId", referencedColumnName = "id")
private ProductCategory productCategoryId;
public ProductToProductCategoryId() {
}
public Product getProductId() {
return productId;
}
public void setProductId(Product productId) {
this.productId = productId;
}
public ProductCategory getProductCategoryId() {
return productCategoryId;
}
public void setProductCategoryId(ProductCategory productCategoryId) {
this.productCategoryId = productCategoryId;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (!(o instanceof ProductToProductCategoryId)) return false;
ProductToProductCategoryId that = (ProductToProductCategoryId) o;
return Objects.equals(getProductId(), that.getProductId()) &&
Objects.equals(getProductCategoryId(), that.getProductCategoryId());
}
@Override
public int hashCode() {
return Objects.hash(getProductId(), getProductCategoryId());
}
}
@Repository
public interface Product2ProductCategoryJpaRepository extends JpaRepository<ProductToProductCategories, ProductToProductCategoryId> {
}
现在,当我尝试在product_2_product_categories
表格中插入一个项目时
public Boolean saveOrUpdate(Long productId, Long productCategoryId) {
Product product = productJpaRepository.findById(productId).get();
ProductCategory productCategory = productCategoryJpaRepository.findById(productCategoryId).get();
ProductToProductCategoryId productToProductCategoryId = new ProductToProductCategoryId();
productToProductCategoryId.setProductCategoryId(productCategory);
productToProductCategoryId.setProductId(product);
product2ProductCategoryJpaRepository.save(new ProductToProductCategories(productToProductCategoryId));
return true;
}
我收到一条错误消息
java.sql.SQLException:字段 'productId' 在 com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.19.罐子:8.0.19]
解决方案
创建一个二级构造函数,默认值为null,如果null不工作就用0,null值会自动替换为自动生成的id
@Entity
@Table(name = "products")
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="id")
private long id;
public Product(long id){
this.id = id;
}
public Product(){
this.id = null;
}
}