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
LONGVARBINARY datatype (LONG VARCHAR FOR BIT DATA). A Derby BLOB can
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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