Hi there,

I have an many-to-many relationship, to which I want to add an additional table. I'm using the instructions here viewtopic.php?f=1&t=950062&start=0

In my many-to-many relationship, I also want the ID to be the connection of the both connected many-to-many relationship. The problem is that, when I create the @IdClass to define this, Hibernate wants to save the whole object to db and not just the id of the entity.

So my question is, how do I tell to hibernate that I want to save only the ID of the object to database, not the whole object?


Here are my classes:

@Entity
public class User implements Serializable {

@OneToMany (targetEntity=Friend.class,mappedBy="user")
private List<Friend> friends = new LinkedList<Friend>();

//I have tried with and without this component, I don't need this if Hibernate doesn't require it
@OneToMany (targetEntity=Friend.class,mappedBy="friend")
private List<Friend> otherFriends = new LinkedList<Friend>();

@Id @GeneratedValue (strategy = GenerationType.AUTO)
private Integer id;

... the getters and setters etc. other data...

}

@Entity
@IdClass(FriendId.class)
public class Friend implements Serializable {
@NotNull
private boolean pending;

@Id
@ManyToOne
@NotNull
private User user;

@Id
@ManyToOne
@NotNull
private User friend;

...the getters and setters ...

}

I have two solutions for the Friend Primary key table:

This one doesn't let the Hibernate to insert the table, but says:
BLOB/TEXT column ‘friend’ used in key specification without a key length
public class FriendId implements Serializable {
private User user,friend;

... the getters and setters...

@Override
public boolean equals(Object o) {
if (o == this) {
return true;
}
else if (o instanceof FriendId) {
return friend.equals(((FriendId)o).friend) &&
user.equals(((FriendId)o).user);
}
return false;
}

@Override
public int hashCode() {
return user.hashCode() ^ friend.hashCode();
}
}

This one creates the table but Hibernate doesn't understand that only the user-id is stored, but looks for the whole object from the database
public class FriendId implements Serializable {
private int user,friend;

... the getters and setters...

@Override
public boolean equals(Object o) {
if (o == this) {
return true;
}
else if (o instanceof FriendId) {
return friend == ((FriendId)o).friend &&
user == (((FriendId)o).user);
}
return false;
}

@Override
public int hashCode() {
return user ^ friend;
}
}

Thanks,

Jesse

My 3 cents:
Hmmm...
Does it solve your problem? --->



When dynamicInsert is set to true, then *only* columns modified by you (for example id column) will be present in SQL INSERT statement generated by you.

Take care!
Adam Wozniak

Didn't seem to help. It caused another Exception. I'm actually using javax.persistence.Entity, and it doesn't seem to have the dynamicInsert variable. Changing to org.hibernate.annotations.Entity causes another Exception.

Nope :)

Don't try to replace avax.persistence.Entity with @org.hibernate.annotations.Entity :)
Just add this as another annotation to you Java class. Something like this:



Take care!
Adam Woźniak
Poland

Hmh, now it just printed the same error message as previously:
BLOB/TEXT column ‘friend’ used in key specification without a key length

So it seems that this doesn't fix the problem.

I want to save these to fields as int (the ID:s) to db and not the whole object:

@Id
@ManyToOne
@NotNull
private User user;

@Id
@ManyToOne
@NotNull
private User friend;

And I don't know how to tell that to the machine.

br,

Jesse

精华啊 不过我已经看过了 哈哈 还是顶下 *^__^*








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为什么是中域互联选择了我，而不是啊红选择了我，为什么？？？

Hi,

Still looking the answer. I actually need another table like that also, so it would be nice to use the proper way.

br,

Jesse

Hi,

Adding ManyToOne annotation to the class defining the PK (FriendId.class in this example) seems to do the trick:

public class FriendId implements Serializable {
@ManyToOne
private User user,friend;

br,

Jesse