Hi all,
I assume this is the right place to ask, please point me elsewhere if not.
I am learning Hibernate and came to such situation:
I have a 1:N relation (invoice (faktura) and it's items (polozky)) mapped
like:
<set name="polozky" table="faktury_polozky" lazy="false"
access="field" fetch="join">
<key column="id_faktura"/>
<composite-element class="fakturace.Polozka">
<property name="nazev" not-null="true" />
<property name="mnozstvi" not-null="true"/>
<property name="jednotka" not-null="true"/>
<property name="cenaJednotky" not-null="true"/>
</composite-element>
</set>
But, 1) When I list() the invoices, upon commit() hibernate DELETEs the
items' rows from the DB and INSERTs them again with same values. No other
action is done; getter returns the same collection object as setter
retrieves; and I set access to "field" anyway. So here's the code:
// LIST
...
else if( "list".equals(args[0]) ){
List res = session.createQuery("FROM Faktura ORDER BY vystaveno
ASC").list();
System.out.println("Nalezeno "+res.size()+" faktur.\n");
for (int i = 0; i < res.size(); i++) {
Faktura f = (Faktura) res.get(i);
System.out.println( f.Vypis() + "\n\n" ); // Vypis() uses
only getters.
}
}
// COMMIT + CLOSE
System.out.println("------------------------- COMMIT");
session.getTransaction().commit();
And the log after commit:
------------------------- COMMIT
Hibernate: delete from faktury_polozky where id_faktura=? and nazev=? and
mnozstvi=? and jednotka=? and cenaJednotky=?
Hibernate: delete from faktury_polozky where id_faktura=? and nazev=? and
mnozstvi=? and jednotka=? and cenaJednotky=?
Hibernate: insert into faktury_polozky (id_faktura, nazev,
mnozstvi, jednotka, cenaJednotky) values (?, ?, ?, ?, ?)
Hibernate: insert into faktury_polozky (id_faktura, nazev,
mnozstvi, jednotka, cenaJednotky) values (?, ?, ?, ?, ?)
... etc., for every invoice (faktury) there's a delete and insert.
So, what's that I do wrong?
And 2), Hibernate does a select for each invoice to get it's items. I wonder
whether this is the 1+N problem, because it is not caused by reading
collection items one by one. I would expect hibernate to fetch all items
with a SELECT like
SELECT ... FROM invoice_items WHERE id_invoice IN ( SELECT id FROM
invoices WHERE ... << the conditions generated from the HQL query >> )
At least that's the way I would do it in MySQL; currently I play with HSQL,
maybe it's not capable of this.
So is this normal?
Thanks for any useful hints.
Ondra Zizka
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