OJB questions

[Ali Ibrahim <ai...@vecna.com>]

Hello,

I had a couple of questions I though someone could answer for me.

1. Why do you have to declare both the key and object variables for 
references?
e.g.

public class A
{

  Integer breferenceId;

  B breference;

}

It seems like you should be able to find the key inside the object 
reference. Maybe I am missing something though.

2. Is there some better documentation of the SQL that should be 
generated for the various types of inheritance + references? The 
tutorials cover the structure of the repository.xml very well, but there 
is little information on what cascade or foriegn key settings OJB 
expects if any.

3. After reading the documentation I realized that auto-delete did NOT 
correspond to a database cascade. Possibly this could be made more 
clear. I assume you expect users to set cascade settings themselves in 
the SQL code (it might nice if OJB could also have settings to do  this 
programatically, especially since the sql cascades can affect the 
integrity of the cache).

4. Is there a way to set tell a broker and only that broker to use a 
certain cache? I know you can have a per-broker cache, but it would be 
nice to have more control of cache so you could have session-level 
caching across broker objects.

5. What happens you proxy an object in an inheritance hierarchy? Are you 
forced to proxy all the classes in the hierarchy? If not, how do you 
deal with the issues of resolving objects from the interface class?

6. I have coded a small example in OJB with inheritance, single and 
collection references, and proxies and it has worked well. We are also 
thinking of using Hibernate. What are some of the differences between 
OJB and Hibernate? (nicely of course).

Thank You.

-- 
Ali Ibrahim
Vecna Technologies
Email: aibrahim@vecna.com
W: (301)864-7253

Date Query

[Cory L Hubert <ch...@alloy.com>]

	This should be simple question :)

	For some reason this query by date isn't working.  The date is a
java.sql.Date.   It's on SQLServer2000 using the OPTA2000 Driver.

====
		PersistenceBroker broker =
PersistenceBrokerFactory.defaultPersistenceBroker();
		broker.beginTransaction();
		Criteria c = new Criteria();
		System.out.println("date :" + d.toString());
		c.addEqualToColumn("event_day", d.toString());
		QueryByCriteria query = new QueryByCriteria(Event.class, c);
		Collection e = broker.getCollectionByQuery(query);
		broker.commitTransaction();
=====

I concated the date like this.

			Calendar cal = Calendar.getInstance();
			cal.clear();
			cal.set(Calendar.MONTH,  3); // really 4 since Jan is 0
			cal.set(Calendar.DATE, 7);
			cal.set(Calendar.YEAR, 2003);
			Date d = new Date(cal.getTime().getTime());

======

And the record in the db is a SQLServer DATETIME filed

2003-04-07 00:00:00.000





-----Original Message-----
From: Larry Schuler [mailto:larryas2@yahoo.com]
Sent: Wednesday, April 09, 2003 5:34 PM
To: OJB Users List
Subject: Re: OJB questions


Hi Ali,
  You asked:
> 1. Why do you have to declare both the key and object variables for
> references?
> e.g.
>
> public class A
> {
>
>  Integer breferenceId;
>
>  B breference;
>
> }
>
> It seems like you should be able to find the key inside the object
> reference. Maybe I am missing something though.

I asked this same question a week or so ago, unfortunately no one responded,
I
ended up adding the dual refs to my objects, but I'm still wondering how
synchronization will be maintained :(

> 6. I have coded a small example in OJB with inheritance, single and
> collection references, and proxies and it has worked well. We are also
> thinking of using Hibernate. What are some of the differences between
> OJB and Hibernate? (nicely of course).

For our use, we had to abandon hibernate because of it's need for a index
field
for all collections. We have a lot of small arrays in our pre-existing
objects
and we didn't like having to create an index for each array in the db.
Otherwise, hibernate seems similar, but the more I work with OJB, the
happier I
am we started using it - just my opinion.

--Larry





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Re: OJB questions

[Larry Schuler <la...@yahoo.com>]

Hi Ali,
  You asked:
> 1. Why do you have to declare both the key and object variables for 
> references?
> e.g.
> 
> public class A
> {
> 
>  Integer breferenceId;
> 
>  B breference;
> 
> }
> 
> It seems like you should be able to find the key inside the object 
> reference. Maybe I am missing something though.

I asked this same question a week or so ago, unfortunately no one responded, I 
ended up adding the dual refs to my objects, but I'm still wondering how 
synchronization will be maintained :(

> 6. I have coded a small example in OJB with inheritance, single and 
> collection references, and proxies and it has worked well. We are also 
> thinking of using Hibernate. What are some of the differences between 
> OJB and Hibernate? (nicely of course).

For our use, we had to abandon hibernate because of it's need for a index field 
for all collections. We have a lot of small arrays in our pre-existing objects 
and we didn't like having to create an index for each array in the db. 
Otherwise, hibernate seems similar, but the more I work with OJB, the happier I 
am we started using it - just my opinion.

--Larry