@ManyToMany —— 双向多对多关联(bidirectional many-to-many association)

理解 解除关联关系 和 删除实体对象

https://www.cnblogs.com/lj95801/p/5011537.html

http://www.cnblogs.com/luxh/archive/2012/05/30/2527123.html

http://www.blogjava.net/rongxh7/archive/2009/06/08/280637.html

https://vladmihalcea.com/the-best-way-to-use-the-manytomany-annotation-with-jpa-and-hibernate/

https://www.jianshu.com/p/54108abb070f

https://www.jianshu.com/p/0ffb8ef64760

https://blog.csdn.net/petercnmei/article/details/54893622

单向关联和双向关联
unidirectional association VS bidirectional association