Re: [Springframework-developer] Exposing LOB support to Jdbc Object layer

[<jue...@we...>]

That looks interesting! I didn't think about overloaded SqlParameter =
constructors before; that definitely makes sense. How to you handle the =
LobCreator lifecycle there? LobCreator.close needs to be invoked after =
PreparedStatement execution (but before transaction completion).

BTW, I've recently refined the LOB support for jdbc.core: There are =
AbstractLobCreatingPreparedStatementCallback and =
AbstractLobStreamingResultSetExtractor classes now (don't we love our =
class naming patterns!), to make LOB handling via JdbcTemplate more =
convenient. Have a look at imagedb's DefaultImageDatabase class for =
usage examples.

There's also a ClobStringType class in our Hibernate support, for =
storing String properties in CLOB fields. That allows to transparently =
store long Strings in Oracle CLOBs respectively MySQL text fields, for =
example. It registers a TransactionSynchronization for the =
LobCreator.close call, so just works within a Spring transaction.

Juergen


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...]On Behalf
Of Thomas Risberg
Sent: Monday, May 03, 2004 2:58 AM
To: spr...@li...
Subject: [Springframework-developer] Exposing LOB support to Jdbc Object
layer


I've recently started to take a closer look at Juergen's LOB handler=20
classes and they look very solid.  It would be a shame not exposing them =

to the Jdbc Object package - primarily SqlUpdate.  I have started to=20
test a few ideas.  I added a constructor accepting a LobHandler to the=20
SqlParameter class.  I also added a SqlLobValue class for holding the=20
input stream and the length.  This is what the usage would look like:

        LobHandler lobHandler =3D new DefaultLobHandler();  // or=20
OracleLobHandler
        String sql =3D "insert into docs (doc_id, description , added,=20
document) values(?, ?, ?, ?)";
        SqlUpdate su =3D new SqlUpdate(ds, sql);
        su.declareParameter(new SqlParameter("id", Types.INTEGER));
        su.declareParameter(new SqlParameter("desc", Types.VARCHAR));
        su.declareParameter(new SqlParameter("added", Types.DATE));
        su.declareParameter(new SqlParameter("lob", Types.BLOB,=20
lobHandler));
        su.compile();
        Object[] inval =3D new Object[4];
        inval[0] =3D new Integer(newId);
        inval[1] =3D "Doc One";
        inval[2] =3D new java.sql.Date(new Date().getTime());
        File in =3D new File("word.doc");
        int len =3D (int) in.length();
        FileInputStream is =3D new FileInputStream(in);
        inval[3] =3D new SqlLobValue(is, len);
        int count =3D su.update(inval);
        is.close();

A few tweaks to the PreparedStatementCreateorImpl class and this=20
actually ran against both Oracle and PostgreSQL.

I think we could easily support all the different methods that=20
LobHandler supports:
 byte[]
 BinaryStream
 String
 AsciiStream
 CharacterStream

Any thoughts or ideas?

Thomas


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