Spring Boot 中的多对多映射问题

Question

我正在尝试在 users 和 products 两个表之间进行多对多映射。我写了他们的实体和存储库，但应用程序仍然出错。如果可以的话，请帮助我，在此先感谢。

错误

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.poc.joins.entities.User.users in com.poc.joins.entities.Product.users

代码sn-ps是

用户

package com.poc.joins.entities;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name = "users")
public class User {
    @Id
    private String username;
    private String password;

    @ManyToMany(cascade = CascadeType.MERGE)
    @JoinTable(name = "users_products",
            joinColumns = {@JoinColumn(name = "username")},
            inverseJoinColumns = {@JoinColumn(name = "id")})
    private Set<Product> products = new HashSet<>();
}
// Getter, setters, constructors are not shown here

产品

package com.poc.joins.entities;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name = "products")
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String p_name;
    private Integer quantity;
    private Float price;
    private Float total;

    @ManyToMany(mappedBy = "users")
    private Set<User> users = new HashSet< >();
}
// Getter, setters, constructors are not shown here

Answer 1

在拥有的实体 (Product) 中，传入拥有关系的字段（在 User 实体中）：

@ManyToMany(mappedBy = "products")
private Set<User> users = new HashSet< >();

最初您告诉 Persistence 提供程序在 User 实体中查找名为 users 的字段，该字段将保存有关关系的所有信息（@JoinTable 等）