Hi i am a beginner when it comes to hibernate, i evaluated using it 2years ago, but due to the fact that i thought that the project i was working on would suffer due to long adaption time i did not pursue it any more.

Now i am working on a much smaller project, still connected to the original one, and i am concidering hibernate again. And one issue came up to me. And i wanted to ask the experts on the best practises when it comes to this specific issue i have.

Let say that i have 3 tables in the database.
1. Competitions
2. Rounds
3. Events

As you might see one competition might have many rounds and one round might have many events.

a. So if i wanted to get all the events for a certain competition i would have to make a join on 3 tables.
b. If i wanted to get the information on the competition i would have to make a query on one table.

Here comes my question.
Because in my application i will query single tables as well as making multiple join tables what is the best practise?
I made one small example to test which is something like this.

I made one xml mapping called TbCompetition.java and Competition.hbm.xml which mappes the class TbCompetition to table Competition, this mapping is a single one, no definitions whatsoever to any other table in the xml

Then i also made another mapping called TbFixture and Fixture.htm.xml and in this file i mapp TbFixture to Competition but i also have
<set name="rounds" lazy="false">
<key column="competition_id" />
<one-to-many class="TbRound" />
</set>

so if i wanted to do a query on the competition just to get the name of the competition i would use the Single object and if i wanted to make a more complex combination i would use the fixture object.

Now this worked just fine... but lets make the whole project a bit more complex and add another... lets say 10 tables, on one to many and many to many connections... everything becomes more unclear to me. Should i make new xml definitions and classes for all my queries in the project or should i define joins and not use them. Or as one recommended to me i should use HQL instead... and define the joins realtime. But HQL dont look that good to me as i would prefer to use getters and setters instead.

So the reason i post this question is to ask what would be the best practise in this case. I have a "BIG" project, alot of tables that are joined back and forth to get the information. What is the best way to do it, not only memory wise...

thanks for your help in advance...

kind regards
Jonny

I would suggest that you start by mapping your original model as is and use HQL for the queries. Then populate your DB with large amounts of data and only when/if you find any performance issues, try different optimization methods (lazy loading, caching, your fixtures etc.).
I think this will help you from spending too much time doing optimizations that you might not need.

Greetings
///Odd Möller

I am doing just this right now... but i do not understand how to loop through the list...
I am sorry to say this to all the hibernate staff but i find your documentation very much incomplete... you never show the all the parts in you examples to see how to proceed from one step to another...

Well here is the code...

StringBuffer buf = new StringBuffer();
buf.append("select c.competitionName, r.roundName, e.eventDate");
buf.append(" from TbCompetition c, TbRound r, TbEvent e");
buf.append(" where c.competitionId = " + arg_competitionId);
buf.append(" and r.competitionId = c.competitionId");
buf.append(" and e.roundId = r.roundId");
Session session = com.xscores.common.util.HibernateUtil.currentSession();
Query c = session.createQuery(buf.toString());

List l = c.list();
com.xscores.common.util.HibernateUtil.closeSession();

if i now want to get the result of this query which is in my List l... how do i do that, what do i cast this object to?

/Jonny

Without knowing what your domain objects look like, I would try something like:

where:


Greetings
///Odd Möller

see [url]http://www.hibernate.org/hib_docs/v3/reference/en/html/queryhql.html#queryhql-select
[/url]

You just need a class to hold your results, with an appropriate constructor of the fields in yur result list.

NB you only need to do this technique if you are running a query to get a subset of columns, not if you want the whole object returned.

well the sollution i was looking for was...
the the List returned is an Object[] it will be Strings in case there is a String field or the Table itself as an object..

/Jonny

I would recommend you buy the book "Hibernate in Action". I started with Hibernate last year. This book was very helpful and I still refer back to it all the time. It is based on Hibernate 2, but, it is still a very good resource for beginners.