Serialization Object and storasge in blob field Oracle 8.1.6

Question

Hi,
this is problem with serializing and deserializing when i am storing object serialized in a Blob field Oracle:
MyObject myObject = new MyObject();
ByteArrayOutputStream bayos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream (bayos);
oos.writeObject(myObject);
oos.flush();
byte[] buffer = bayos.toByteArray();
int size = buffer.length;
oos.close();
ByteArrayInputStream bayis = new ByteArrayInputStream(buffer,0,size);
// if the number bytes of serialized myObject > 4kbytes then the insert in Blob field fails down.
// if the number bytes of serialized myObject < 4kbytes then the insert in Blob field successes.
// So I only can put in Blob field serialized object with size minus 4k.
// The code for insert:
PreparedStatement pstmt = connection.prepareStatement(sqlInsert);
pstmt.setBinaryStream(1,bayis,size);
int retCode = pstmt.executeUpdate();
// The code for read from table Oracle
rset = stmt.rxecuteQuery(sqlSelect);
rset.next();
oracle.sql.BLOB fldBlob = (BLOB)rset.getObject(1);
InputStream ins = fldBlob.getBinaryStream();
byte[] buf = new byte[size]
ByteArrayInputStream bayis = new ByteArrayInputStream(buf,0,size);
ObjectInputStream ois = new ObjectInputStream(bayis);
MyObject myObject = (MyObject)ois.readObject();
Someone knows the reason of the limit of 4Kbyte ?
Thanks....

Answer 1

Insert LOBs into Oracle is a 3 step process. You must insert a place holder, and the do a select for update to put the contents into the row. Lets say you have a table called MY_LOB:
create table MY_LOB (
   MYID NUMERIC(10) NOT NULL,
   MYLOB BLOB DEFAULT EMPTY_BLOB()
);The 'empty_blob' keyword tells Oracle to put a dummy value in the blob column when a row is initially created. To insert (assuming you have a db connection already):
conn.setAutoCommit(false);
PreparedStatement pstmt = null;
ResultSet rs = null;
oracle.sql.BLOB myLob = null;
try
   //Insert the initial row.
   pstmt = conn.prepareStatement("INSERT INTO MY_LOB (MYID) VALUES (?)");
   //Set the PK value
   pstmt.setInt(1,100);
   pstmt.executeUpdate();
   pstmt.close();
   //Lock the row for insertion.  This is needed for large inserts.
   pstmt = conn.prepareStatement("SELECT MYLOB from MY_LOB where MYID = ? FOR UPDATE");
   pstmt.setInt(1,100);
   rs = pstmt.executeQuery();
   if (rs.next())
      myLob = (oracle.sql.BLOB)rs.getBlob(1);
   rs.close();
   pstmt.close();
   //Finally...update the row with the blob data....
   myLob.putBytes(1, buffer);
   pstmt = conn.prepareStatement("UPDATE MY_LOB SET MYLOB = ? WHERE MYID = ?");
   pstmt.setBlob(1, myLob);
   pstmt.setInt(2,100);
   pstmt.executeUpdate();
   pstmt.close();
   conn.commit();
catch(SQLException sqlE)
    conn.rollback();
finally
  //make sure and close all statements....
}Hope this helps, I didn't compile it so it may have some bugs. It should lead in the right direction at least.