String qry = "select data from mtable where id = " + id;
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(qry);
 if  (rs.next()) {
  InputStream in = rs.getBinaryStream("data");
  BufferedInputStream bin =  new  BufferedInputStream(in);
   int  readed = - 1 ;
   while  ((readed = bin.read()) != - 1 ) {
    out.write(readed); // out в данном случае - OutputStream некого сервлета
  }
  bin.close();
}
rs.close();
st.close();

File file =  new  File("c:\\content.doc");
FileBlobImpl fblob =  new  FileBlobImpl(file);
String qry = "update mtable set data = ? where id = " + id;
PreparedStatement pst = con.prepareStatement(query);
pst.setBlob( 1 , fblob);
pst.executeUpdate();
pst.close();

 import  java.sql.*;
 import  java.io.*;

 public   class  FileBlobImpl  implements  Blob {
   private  File file;

   public  FileBlobImpl(File file) {
     this .file = file;
  }

   public   long  length()  throws  SQLException {
     return  file.length();
  }

   public   byte [] getBytes( long  pos,  int  length)  throws  SQLException {
     if  (pos + length >= length())
       throw   new  SQLException("Bad lenght");

     try  {
      RandomAccessFile raf =  new  RandomAccessFile(file, "r");
      raf.seek(pos);
       byte [] bytes =  new   byte [length];
       for  ( int  i =  0 ; i < bytes.length; i++) {
        bytes[i] = raf.readByte();
      }
       return  bytes;
    }  catch  (FileNotFoundException e) {
       throw   new  SQLException("File is not found :" + e.toString());
    }  catch  (IOException e) {
       throw   new  SQLException("IO Exception while reading this file:" + e.toString());
    }
  }

   public  InputStream getBinaryStream()  throws  SQLException {
     try  {
       return   new  FileInputStream(file);
    }  catch  (FileNotFoundException e) {
       throw   new  SQLException("File is not found :" + e.toString());
    }
  }

   public   long  position( byte  pattern[],  long  start)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }

   public   long  position(Blob pattern,  long  start)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }

   public   int  setBytes( long  pos,  byte [] bytes)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }

   public   int  setBytes( long  pos,  byte [] bytes,  int  offset,  int  len)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }

   public  OutputStream setBinaryStream( long  pos)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }

   public   void  truncate( long  len)  throws  SQLException {
     throw   new  UnsupportedOperationException();
  }
}