ManyToMany mapping and collections questions

pooter8d · **Joined:** Wed Mar 05, 2008 10:32 am **Posts:** 48

I would like to create a Many-To-Many mapping using annotations but my MappedBy column is incorrect. My 2 objects are a UserEnt and an EventEnt. I want the EventEnt to contain a set of invited users to the event. At the same time, I want each user to have a set of events, they have been invited to. Thus calling for an M-M mapping. This is what I currently have and I have tried several column names under the MappedBy property only to have an error pop up.
UserEnt class

Code:

@ManyToMany (cascade = {CascadeType.PERSIST, CascadeType.MERGE })
@org.hibernate.annotations.Cascade(value = org.hibernate.annotations.CascadeType.SAVE_UPDATE)
public Set<UserEnt> getInviteList() {  
  return inviteList;
}

EventEnt class

Code:

@ManyToMany(mappedBy="users")
public Set<EventEnt> getInviteList() {  
  return inviteList;
}

My second question is concerning a set of object inside that object. Now I know how to annotate the getter method, but I don’t know how to properly create “add” and “remove” methods for the sets. This is also in the UserEnt class as I want to give every user a “friends” list (Set<UserEnt>). This is what I currently have and I’ve been using the same block (altered for other objects) but on sets that were of a different object.

Code:

@org.hibernate.annotations.CollectionOfElements(fetch=FetchType.LAZY)
public Set<UserEnt> getFriends() {  
  return friends;
} 

public void addFriend(UserEnt friend){ 
  if (friend == null)    
    throw new IllegalArgumentException("adding null friend"); 
  this.friends.add(friend); 
  friend.setFriends(this);
}

My hiccup is in the final line of code: friend.setFriends(this) where my setFriends method only accepts a Set<UserEnt> and not just a UserEnt.

Help for either of these would be highly appreciated! Thanks!
P.S. I think the search capability of this forum is broken..

andydale · **Posted:** Wed Mar 05, 2008 12:11 pm

Hi,

I think for you should try the following value for mappedBy

@ManyToMany(mappedBy="inviteList")

Cheers,

Andy

pooter8d · **Joined:** Wed Mar 05, 2008 10:32 am **Posts:** 48

I've fixed my M-M problem.. here is the code for others to look at. I also had problems with the defualt lazy fetching, so i had to force it to eager.

UserEnt

Code:

@ManyToMany(cascade={CascadeType.PERSIST, CascadeType.MERGE},   fetch=FetchType.EAGER, mappedBy="inviteList", targetEntity=EventEnt.class)
public Set<EventEnt> getInviteList() {
   return inviteList;
}

EventEnt

Code:

@ManyToMany (targetEntity=com.epixentertainment.model.UserEnt.class, cascade = {CascadeType.PERSIST, CascadeType.MERGE }, fetch=FetchType.EAGER)
@JoinTable(name="event_userinvite", joinColumns={@JoinColumn(name="event_id")},   inverseJoinColumns={@JoinColumn(name="user_id")})
@org.hibernate.annotations.Cascade(value = org.hibernate.annotations.CascadeType.SAVE_UPDATE)
public Set<UserEnt> getInviteList() {
 return inviteList;
}

still working on that other one though!

carlolf · **Posted:** Thu Mar 06, 2008 3:34 am

pooter8d wrote:

@ManyToMany (targetEntity=com.epixentertainment.model.UserEnt.class, cascade = {CascadeType.PERSIST, CascadeType.MERGE }, fetch=FetchType.EAGER)
@JoinTable(name="event_userinvite", joinColumns={@JoinColumn(name="event_id")}, inverseJoinColumns={@JoinColumn(name="user_id")})
@org.hibernate.annotations.Cascade(value = org.hibernate.annotations.CascadeType.SAVE_UPDATE)
public Set<UserEnt> getInviteList() {
return inviteList;
}

Sorry for my "dummyness": but what exactly does

Code:

org.hibernate.annotations.CascadeType.SAVE_UPDATE)

?

And what is the difference to JPA's

Code:

cascade = {CascadeType.PERSIST, CascadeType.MERGE }

?
Can anyone from the Annotations team answer this?

Carlo

damonf · **Joined:** Wed Dec 21, 2005 6:57 pm **Posts:** 70

public void addFriend(UserEnt friend){
if (friend == null)
throw new IllegalArgumentException("adding null friend");
this.friends.add(friend);
friend.setFriends(this);
}

try

Code:

friend.getUserEntities().add(this);