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<Product> 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<Product> getProducts() {

        return products;

    }

    public void setProducts(Set<Product> 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：