I get a lazyInitializationException. The mapping are a many-to-many association, but i use 2 one-to-many association to implement it.

<class name=User...>
..
<set name="myItems" lazy="true" inverse="true" cascade="all-delete-orphan">
<key column="USER_ID" />

<one-to-many class="Sign"/>
</set>
</class>


<class name="Signed" ...
<many-to-one name="item" column="ITEM_ID" class="Item"/>
<many-to-one name="user" column="USER_ID" class="User"/>
</class>

<class name="Item"...
..
<!-- no one-to-many here because i don't need in my application...it is right? -->

<many-to-one name="category" column="cat_id" class="Category" />
</class>

In one session i do
Signed s = new Signed();
s.setItem(item);
s.setUser(user);
user.getMyItems().add(sign);


in the next session i do in a jsp:

<bean:write name="sign" property="item.title"/> (OK!)
<bean:write name="sign" property="item.category.description"/> (lazy exception!)

The session is open in my JSP, so why this lazy object initialization problem??
And this happens only when I add an item to the set "myItems" (in the user class) and in the next session I navigate on the object graph as i showed in the code above.

Incredible (for me), but if I do
user = dao.getUserById(user.getId());
before the code above everything is ok!

Instead yesterday i tried
session.update(utente);
and
session.lock(utente, LockMode.NONE);
wothout good results!

WHY?