单向N-N关联必须使用连接表。

Company实体：

package com.ydoing.hibernate5;import java.util.HashSet;import java.util.Set;import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.JoinTable;import javax.persistence.ManyToMany;import javax.persistence.Table;@Entity@Table(name = "company_inf")public class Company {
          @Id    @Column(name = "company_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private Integer id;    private String name;    @ManyToMany(targetEntity = Product.class, cascade = CascadeType.ALL)    @JoinTable(name = "company_product", joinColumns = @JoinColumn(name = "company_id", referencedColumnName = "company_id"), inverseJoinColumns = @JoinColumn(name = "product_id", referencedColumnName = "product_id"))    private Set
      
        products = new HashSet<>();    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Set
       
         getProducts() {        return products;    }    public void setProducts(Set
        
          products) {        this.products = products;    }}
        
       
      

Product实体：

package com.ydoing.hibernate5;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "product_inf")public class Product {
          @Id    @Column(name = "product_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private Integer id;    private String name;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

Console输出：

Hibernate:     insert     into        company_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        product_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        product_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        company_product        (company_id, product_id)     values        (?

, ?

) Hibernate: insert into company_product (company_id, product_id) values (?

, ?

)

从输出不难看出。Hibernate创建了连接表company_product。

数据库表：