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From Dies K <di...@fast.au.fujitsu.com>
Subject Re: setNull with BLOB column
Date Sat, 27 Jun 2009 04:27:57 GMT

Hi Rick,

I will contact the Toplink developers about this and see if this can/should
be fixed.


Rick Hillegas-2 wrote:
> Hi Dies,
> I am not an expert on Toplink or its default datatype mappings for 
> Derby. I think that LONGVARBINARY is a better mapping for byte[] and I 
> would reserve BLOB as the mapping for columns which you really want to 
> manipulate using the java.sql.Blob methods. It may be that BLOB is the 
> default mapping because it can hold more bytes than the Derby 
> hold up to 2,147,483,647 bytes while a Derby LONG VARCHAR FOR BIT DATA 
> can only hold up to 32,700 bytes.
> I don't know why Toplink is trying to put a LONGVARBINARY NULL into a 
> column of type BLOB. The javadoc for PreparedStatement.setNull() states 
> that the type of the NULL must be the type of the column. So I would 
> expect that the code would do this instead:
>   ps.setNull( n, java.sql.Types.BLOB );
> Again, I'm not an expert on the O/R mapping frameworks, but I get the 
> impression that it is fairly easy to tweak their vendor-specific 
> datatype mappings. If your byte[] fields aren't longer than 32,700 bytes 
> and you don't use the java.sql.Blob methods, then LONG VARCHAR FOR BIT 
> DATA ought to work for you.
> Hope this helps,
> -Rick
> Dies Koper wrote:
>> Hi,
>> I have a JPA application and use Toplink as persistence provider.
>> Toplink has a table creation option. It maps persistence fields of Java
>> type byte[] (without @Lob annotation) to BLOB when using Derby.
>> (LONGVARBINARY on Oracle DB).
>> Is BLOB the recommended mapping for fields of type byte[]?
>> I'm seeing the following issue with this because of the changes made in
>> DERBY-1610:
>> If I do not initialize the byte[] field (i.e. leave it null) and persist
>> the entity object, Toplink calls setNull(n,
>> java.sql.Types.LONGVARBINARY), leading to the following exception:
>> Caused by: java.sql.SQLException: An attempt was made to get a data
>> value of type 'LONGVARBINARY' from a data value of type 'BLOB'.
>> 	at
>> org.apache.derby.client.am.SQLExceptionFactory.getSQLException(Unknown
>> Source)
>> 	at org.apache.derby.client.am.SqlException.getSQLException(Unknown
>> Source)
>> 	at org.apache.derby.client.am.PreparedStatement.setNull(Unknown Source)
>> 	at
>> oracle.toplink.essentials.internal.databaseaccess.DatabasePlatform.setComplexParameterValue(DatabasePlatform.java:1438)
>> From a google search I found a lot of discussions on the Derby mailing
>> lists/issue tracker about adding such error checks and making them
>> consistent, but I also had the idea some issues were left unresolved.
>> Are there any plans to make changes to allow the above combination?
>> Or would your opinion be that Toplink should change its default column
>> type for byte[]?
>> Thanks,
>> Dies

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