ManyToOne, OneToMany, ManyToMany

http://download.oracle.com/javaee/6/api/javax/persistence/ManyToOne.html

@ManyToOne(optional=false)
@JoinColumn(name="CUST_ID", nullable=false, updatable=false)
public Customer getCustomer() { return customer; }



http://download.oracle.com/javaee/6/api/javax/persistence/OneToMany.html

@OneToMany(cascade=ALL, mappedBy="customer")
public Set getOrders() { return orders; }



the first is always "me", the second is "the other"

ManyToOne means "there are many of me for one of them" -> hence I have only 1 of them, and he has a Set of me

OneToMany means "there is one of me for many of them" -> hence I have a Set of them


http://download.oracle.com/javaee/6/api/javax/persistence/ManyToMany.html

@ManyToMany
@JoinTable(name="CUST_PHONES")
public Set getPhones() { return phones; }


I have a Set of them, and they have a Set of me