ManyToMany

有3张表，calendar,calendar_user,user
calendar_user为中间表只保存calendar_id,user_id，calendar_user表没有实体对象,

private Set<User> users;

@ManyToMany(  
        targetEntity=User.class, 
        cascade={CascadeType.PERSIST}//防止删除子时删除父
       
    )
    @JoinTable(
        name="calendar_user",
        joinColumns={@JoinColumn(name="calendar_id")},
        inverseJoinColumns={@JoinColumn(name="user_id")}
    )
 public Set<User> getUsers() {
  return users;
 }

 public void setUsers(Set<User> users) {
  this.users= users;
 }