spring-boot - @ManyToMany 休眠映射的问题
问题描述
我是网络开发的新手。我一直在尝试制作一个电子商务平台,并使用之间的@ManyToMany
映射product
和用作连接表。wishlist
wishlist_product
添加后,我没有遇到错误,但数据未添加到连接表中。我已经尝试解决此问题 2 天了,但一直面临持续失败。我已经附上了这两个wishlist
和product
下面的代码。
@Entity
@Table(name = "wishlist")
public class Wishlist {
@Id
@Column(name = "username")
/*
* @GeneratedValue(generator = "gen")
*
* @GenericGenerator(name = "gen", strategy = "foreign", parameters
* = @Parameter(name = "property", value = "login"))
*/
private String username;
@ManyToMany
@JoinTable(name = "wishlist_product",
joinColumns = @JoinColumn(name = "username"),
inverseJoinColumns = @JoinColumn(name = "product_id"))
private List<Electronics> product;
@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@Table(name = "electronics")
@DiscriminatorColumn(name = "product_Type", discriminatorType = DiscriminatorType.STRING)
public class Electronics {
@Id
@GenericGenerator(name = "CamIdGenerator", strategy = "com.virtusa.neuralhack.vlx.IdGenerator.CameraIdGenerator")
@GeneratedValue(generator = "CamIdGenerator")
// @GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "product_id")
private String productId;
private String askingPrice;
@Column(name = "age")
private String howOld;
@Column(name = "model")
private String model;
@Column(name = "brand")
private String brand;
@Column(name = "description")
private String description;
transient private String email;
@ManyToOne
@JoinColumn(name = "username")
private User_Login user;
@ManyToMany
@JoinTable(name = "wishlist_product", joinColumns = @JoinColumn(name = "product_id"), inverseJoinColumns = @JoinColumn(name = "username"))
private List<Wishlist> wishlist;
public void addToWishlist(String email, String productId) {
Session currentSession = manager.unwrap(Session.class);
Wishlist wishlist = currentSession.get(Wishlist.class,email);
//System.out.println(wishlist.getUser());
Electronics product = currentSession.get(Electronics.class, productId);
System.out.println(product);
wishlist.addToWishlist(product);
//product.addAWishlist(wishlist);
//System.out.println(wishlist.getProduct().get(0));
currentSession.saveOrUpdate(wishlist);
}
解决方案
你应该这样做:
@Entity
@Table(name = "wishlist")
public class Wishlist {
@Id
@Column(name = "username")
private String username;
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
@JoinTable(name = "wishlist_product",
joinColumns = @JoinColumn(name = "username"),
inverseJoinColumns = @JoinColumn(name = "product_id"))
private List<Electronics> products;
public void addProduct(Electronics product) {
products.add( product );
product.getWishlists().add( this );
}
public void removeProduct(Electronics product) {
products.remove( product );
product.getWishlists().remove( this );
}
}
@Entity
@Table(name = "electronics")
public class Electronics {
@Id
@Column(name = "product_id")
private String productId;
@ManyToMany(mappedBy = "products")
private List<Wishlist> wishlists;
}
注释只能映射双向 的拥有方。你应该在另一边使用。
@ManyToMany
@JoinTable
mappedBy
cascade
如果要传播持久状态和其他状态,则应在拥有方设置属性。为了保持双方之间的同步性,提供添加或删除子实体的辅助方法是一种很好的做法。
您的addToWishlist
方法将如下所示:
public void addToWishlist(String email, String productId) {
Session currentSession = manager.unwrap(Session.class);
Wishlist wishlist = currentSession.get(Wishlist.class,email);
Electronics product = currentSession.get(Electronics.class, productId);
wishlist.addProduct(product);
currentSession.saveOrUpdate(wishlist);
}
推荐阅读
- debugging - 如何在 web2py 中启用调试?
- python - 在不同列中比较 Pandas DataFrame 中的前行值
- r - 根据R中另一行的值选择行
- java - 如何在 Android Studio 中实现 Parcelable 多个类
- jenkins - 当我们执行命令“npm run
--silent" 在詹金斯它失败了 - aggregate - 在 Traefik 中聚合两个 API 的结果
- workbox - Workbox-webpack-plugin nested urls sw registration
- visual-studio - 构建 Xamarin 移动应用程序时出现未知的 MSBuild 失败
- python - HttpResponseMessage 在 .NET 中返回 403
- python - 2D 列表 python 无法正确处理