Difference between owned one to many relationship and owned one to many bidirectional relationship(Google App Engine Java Api)

问题

what is the difference between owned one to many relationship and owned one to many bidirectional relationship i read the article below but i don't understand it. Article

回答1:

The owned one to many bidirectional relationship just means that the children have a reference to the parent. For example, the child below can access the parent via persistentUser. If persistentUser didn't exist in the PersistentLogin class then it would not be bidirectional.

One-to-Many (PersistentUser.java - Parent):

@OneToMany(mappedBy = "persistentUser", cascade = CascadeType.ALL)
private Collection<PersistentLogin> persistentLogins;

Many-to-One (PersistentLogin.java - Child):

@ManyToOne(fetch = FetchType.LAZY)
private PersistentUser persistentUser;

回答2:

Finally i understand it.Guess i have a Class Named FootBallTeam and it has a property named teamname. Now the pseudue code is

   FootBallTeam ft = new FootBallTeam();
    ft.setteamname("Barcelona");

then add 3 Player Class entity under this team named Messi,Xavi,Iniesta. now if the relationship is bidirectional when i run the code below,

   ft.setteamname("Real Madrid");

it automatically runs the below codes behind the scenes.

Messi.setteamname("Real Madrid")
Xavi.setteamname("Real Madrid")
Iniesta.setteamname("Real Madrid")

来源：https://stackoverflow.com/questions/2981298/difference-between-owned-one-to-many-relationship-and-owned-one-to-many-bidirect