Hi,
I'm using a Oracle 9i and both BLOB and CLOB fields. OBJ automatically convert those
into byte[] respectvely String fields. My concern is that it really does so since it
would be much nicer if it maps them to Blob and Clob instances and does not read from
the stream before actually accessing such.
Regards,
Mario
-----Original Message-----
From: Theo Niemeijer [mailto:[EMAIL PROTECTED]
Sent: Thu 3/27/2003 3:17 PM
To: OJB Users List
Cc:
Subject: RE: [DBMS] MS SQL Server
Max,
Have not tried it, sorry. My problem with CLOB fields (and BLOB fields) is
that they are not really "Object Oriented" in JDBC: AFAIK
you would have to use _streams_ for input and output wouldn't you ?
(I have used BLOB's in Oracle in a previous Bea Weblogic based
JSP/servlet/JDBC website project, for storing uploaded images and
retrieving them lateron to write them to the webserver filesystem. I remember
I had to open the uploaded file as a stream, give this
stream to JDBC, and on retrieval I got a stream handle back).
I would have no idea how to use this all the way through OJB, so please
enlighten me on this:
We use these "TEXT" fields in the database,and these are mapped to JDBC type
"LONGVARCHAR", to
get the same effect as a CLOB (Character Large OBject isn't it?), namely to
store arbitary long strings in the database. (By the
way, we use OJB 0.9.5 with JBoss in production, and are moving to OJB 1.0rc?
when we feel confident that nothing got broken in our
application. So maybe support for CLOB's is different from 0.9.5, and I do not
really have initimate knowledge of all the low-level
parts of OJB anyway. Would OJB automatically convert a string datatype to a
CLOB stream or something ?)
Why would you want to use CLOB's ?
By the way: This is the class descriptor for the TextBlock object:
<class-descriptor
class="nl.casthere.uib.ojb.Textblock"
table="@[EMAIL PROTECTED]"
>
<field-descriptor id="1"
name="id"
column="id"
jdbc-type="INTEGER"
primarykey="true"
autoincrement="true"
/>
<field-descriptor id="2"
name="ojbConcreteClass"
column="ojb_concrete_class"
jdbc-type="VARCHAR"
/>
<field-descriptor id="3"
name="text"
column="text"
jdbc-type="LONGVARCHAR"
/>
</class-descriptor>
> -----Oorspronkelijk bericht-----
> Van: Geigl Maximilian, R235 [mailto:[EMAIL PROTECTED]
> Verzonden: donderdag 27 maart 2003 14:51
> Aan: OJB Users List
> Onderwerp: AW: [DBMS] MS SQL Server
>
>
> Hello Theo,
>
> thanks a lot for you exhaustive explanations. Just one question left (just
to be sure): I cannot handle
> java.sql.Types.CLOB fields with the driver, I'm I right?
>
> Max
>
> > -----Ursprüngliche Nachricht-----
> > Von: Theo Niemeijer [mailto:[EMAIL PROTECTED]
> > Gesendet: Donnerstag, 27. März 2003 14:29
> > An: OJB Users List
> > Betreff: RE: [DBMS] MS SQL Server
> >
> >
> >
> > We are using the Microsoft JDBC driver from the MS website.
> >
> > We do not have problems with it, and use it in production
> > together with OJB for a medium-size website application with content
> > management services. Using it with success since september 2002.
> >
> > There are lots of (expensive) commercial JDBC drivers for MS
> > SQL Server 2000, but I really do not know what the difference
> > would be.
> > Maybe performance or scalability, but we have not experienced
> > problems in those area's.
> >
> > There is an issue related to OJB:
> > We make use of TEXT fields to circumvent the small 8000 bytes
> > maximum row size for some columns (with some string fields the
> > possible total size could not be guaranteed to be that under
> > 8000 bytes) and found that we needed to create separate reference
> > objects for those. So we have TextBlock objects. This is
> > because MSSQL server can not (will not) do sorting or distinct on TEXT
> > fields. Because OJB will always use all possible fields of a
> > mapped object extent these TEXT fields gave problems, so we
> > mapped them
> > to seperate objects and use auto-retrieve, auto-update etc.
> > on them so the object behaves just like it would be if the TEXT fields
> > were part of the table.
> >
> > There is another issue, but that has more to do with JDBC
> > standards and the way they can use Unicode. We found that
> > Unicode in Java
> > strings will be converted by the JDBC driver to 8-bits ANSI
> > codes (Windows CP1252 I think) unless you would use special JDBC
> > functions. Or something like that, it was not completely
> > clear to me what happened. So the "eur" sign (20AC or
> > something in Unicode)
> > would correctly be stored, and lots of Western Language
> > special characters etc. (as long as they are in Microsofts
> > CP1252 codepage,
> > but not Chinese or other Eastern Language characters. We use
> > VARCHAR, not NVARCHAR, because AFAIK thet would limit the total row
> > width to an even more crippling 4000 characters (the 8000
> > bytes database page size). (So if you have 8 NVARCHAR fields
> > they can all
> > be 500 chars, or one can be 3200 and the others 100 chars
> > :-(. Difficult to explain to your customers complaining about
> > the database
> > errors they got.)
> >
> > So all in all we have no problems with the MS SQL JDBC
> > driver, and would be interested to hear what others found about it.
> >
> > Regards,
> > Theo Niemeijer
> >
> > > -----Oorspronkelijk bericht-----
> > > Van: Geigl Maximilian, R235 [mailto:[EMAIL PROTECTED]
> > > Verzonden: woensdag 26 maart 2003 10:23
> > > Aan: OJB Users List
> > > Onderwerp: [DBMS] MS SQL Server
> > >
> > >
> > > Hello,
> > >
> > > I need to connect to MS SQL Server 2000 and think I must
> > get along with the MS JDBC driver, as it is free for our
> > > customers and doesn't need extra licensing of fees.
> > > Does anybody have experiences with Microsoft SQL Server
> > 2000 Driver for JDBC, Service Pack 1 (is it the latest)?
> > > As far as I understand, it cannot handle CLOB fields, it this right?
> > > Does anybody know of an alternative jdbc driver for sql
> > server, which is free of charge and/or redistributable?
> > >
> > > Thanks
> > > Max
> > >
> > >
> >
> >
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> >
> >
>
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