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From Michael Watzek <mwa.t...@spree.de>
Subject Re: Binding a char to PreparedStatement
Date Wed, 20 Jul 2005 15:49:31 GMT
Hi Andy,

I extended the test program to make objects persistent using JPOX in 
addition to the JDBC test I described below:

There is a persistence capable class having a field of type "char".
There is a table having a single column of type "CHAR(1)". The orm 
metadata for this class specifies a field mapping from the "char" field 
to the "CHAR(1)" column. The orm column attribute "jdbc-type" is 
omitted. Thus, the JPOX default is used.

When an object is made persistent using that mapping, then Derby throws 
error 22001 (see below).

But if the mapping contains the orm column attribute "jdbc-type" setting 
it to "CHAR" explicitly, then Derby does not throw that error. Instead, 
pm.makePersistent succeeds.

It seems, that JPOX does not default orm column attribute "jdbc-type" to 
"CHAR" if the field is of type "char" or "java.lang.Character". Instead, 
JPOX defaults to a numerical type, e.g. "INTEGER". Can you verify that?

Craig,

the spec specifies in chapter 18.5:

"The jdbc-type attribute declares the type of the column in the 
database. This type is defaulted based on the type of the field being 
mapped."

Does this mean, that an implementation may choose for an default?

Another question: The TCK orm metadata does not specify column attribute 
"jdbc-type". Thus, implementations use their default when the TCK runs. 
Does it make sense, to add the jdbc type to all column attributes 
ensuring that the mapping fits to the database schema?

Regards,
Michael

> Hi Michael,
> 
> 
>>we have a lot of derby errors "ERROR 22001: A truncation error was
>>encountered trying to shrink CHAR 'XXX' to length 1."
> 
> 
> I've never seen one of these in our testcases, so we've got some difference in 
> how the TCK is specifying things and how we've done it.
> 
> 
>>I analysed the problem writing a little Java program that uses JDBC
>>directly. The program inserts a row into a table having a single CHAR(1)
>>column. The program uses a prepared statement and binds a Java character
>>  to it using different methods:
>>
>>1) PreparedStatement.setShort
>>2) PreparedStatement.setInt
>>3) PreparedStatement.setObject
>>4) PreparedStatement.setString
> 
> 
> What type is the Java type and what type is the DB column ? (and is there a 
> jdbc-type specified in the MetaData?). Give an example of a Java field, its 
> MetaData entry, and the RDBMS column type and we should be able to isolate 
> this [OK, I could run the TCK and try to find one, but since you have these 
> fresh in your memory its easier to ask you :-)]
> 
> JPOX could use many different JDBC methods depending on what Java type and 
> what RDBMS type so it depends on your situation. For example :-
> Java=char/Character, RDBMS="INTEGER", uses JDBC setInt()
> Java=char/Character, RDBMS="CHAR", uses JDBC setString()
> 
> 


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Michael Watzek                  Tech@Spree Engineering GmbH
mailto:mwa.tech@spree.de        Buelowstr. 66
Tel.:  ++49/30/235 520 36       10783 Berlin - Germany
Fax.:  ++49/30/217 520 12       http://www.spree.de/
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