Re: JDBC Blob helper class & streaming uploaded data into PG

>
>> Does anybody have a JDBC Blob helper class so we can use the
>> setBlob()/getBlob() calls in JDBC for PG 8.3? It would be a class
>> that implements the java.sql.Blob interface.
>
> You really ought to use the driver's Blob implementation. Right now
> creating a new Blob isn't terribly straightforward. In theory the
> JDBC 4 method Connection.createBlob should be used, but that has not
> been implemented in the postgresql driver yet.
>
> The best way to do this at the moment is to insert a row with an empty
> blob, retrieve that blob and then write data into it.
>
> CREATE TABLE test (id int, bigdata oid);
>
> INSERT INTO test VALUES (1, lo_creat(-1));
>
> ResultSet rs = stmt.executeQuery("SELECT bigdata FROM test WHERE id =
> 1");
> rs.next();
> Blob blob = rs.getBlob(1);
> OutputStream out = blob.setBinaryStream(1);
> // from java.util.zip. to compress the data.
> GZIPOutputStream gz = new GZIPOutputStream(out);
> while (!done) {
> gz.write(your data);
> }
> gz.close();
> rs.close();
>
> Kris Jurka

Thanks, Kris. Interesting the create empty blob and then update is used
since Oracle seems to require something similar, though we don't do much
with Oracle any more, I do recall using the EMPTY_BLOB() function and
then updating it after getting an Oracle specific Blob class.

Yeah, that's why we need a Blob class that implements streaming through
the java.sql.Blob interface. We have our own and use simple code like
the following to INSERT (and it works for UPDATE, too):

YoByteBlob ybb = new YoByteBlob(encryptedCompressedData);
stmt.setBlob(1, ybb);

When SELECTING, we can use:
java.sql.Blob dbBlob = rs.getBlob(1);
YoByteBlob ybb = new YoByteBlob(dbBlob);

These work for us now, but our version only supports "all in memory"
byte arrays and no streaming. I could share YoByteBlob if anybody was
interested, but we'll need to do more work to make it all work so we can
stream the data in and out.

David