1. In one to many and many to many, the default value for inverse is false. According to the hibernate reference: the non-inverse side is used to save the in-memory representation to the database. The non-inverse side That is, the end where inverse=false. Generally, the one to many relationship is set to inverse=true on one end, meaning that the relationship is maintained by multiple parties. One advantage is that all relevant records from multiple parties will not need to be updated just because one party makes a single modification; Many to many relationships can be set to inverse=true at either end. 2 Unaved value null, any, none is mainly used to determine whether the hidden objects on the object chain are inserted or updated to the database during cascade insert/update. Generally, when creating a POJO primary key as an object, it defaults to null. In this case, insertion is performed; Otherwise, the POJO is loaded from the database and needs to be updated. I am not very clear about the settings for ‘none’ and ‘any’.