WritableByteChannel into BLOB

i have this method:

 public final int copyStreams(InputStream in, OutputStream out, long sizeLimit) throws IOException
{
    int byteCount = 0;
    IOException error = null;

    long totalBytesRead = 0;

    try
    {
        byte[] buffer = new byte[BYTE_BUFFER_SIZE];
        int bytesRead = -1;
        while ((bytesRead = in.read(buffer)) != -1)
        {
            // We are able to abort the copy immediately upon limit violation.
            totalBytesRead += bytesRead;
            if (sizeLimit > 0 && totalBytesRead > sizeLimit)
            {
                StringBuilder msg = new StringBuilder();
                msg.append("Content size violation, limit = ")
                   .append(sizeLimit);

                throw new ContentLimitViolationException(msg.toString());
            }

            out.write(buffer, 0, bytesRead);
            byteCount += bytesRead;
        }
        out.flush();
    }
    finally
    {
        try
        {
            in.close();
        }
        catch (IOException e)
        {
            error = e;
            logger.error("Failed to close output stream: " + this, e);
        }
        try
        {
            out.close();
        }
        catch (IOException e)
        {
            error = e;
            logger.error("Failed to close output stream: " + this, e);
        }
    }
    if (error != null)
    {
        throw error;
    }
    return byteCount;
}

and this is my main:

 public static void main (String[] arg)
{
    InputStream in = new FileInputStream("pathToMyFile");
    ContentLimitProvider contentLimitProvider = getContentLimitProvider();
    final long sizeLimit = contentLimitProvider.getSizeLimit();

    int byteCount = sizeLimitedStreamCopier.copyStreams(in, out, sizeLimit);

    return byteCount;
}

and this is the method i'm forced to use to build my outputStream

public OutputStream getContentOutputStream() throws ContentIOException
{
    try
    {
        WritableByteChannel channel = getWritableChannel();
        OutputStream is = new BufferedOutputStream(Channels.newOutputStream(channel));
        // done
        return is;
    }
    catch (Throwable e)
    {
        throw new ContentIOException("Failed to open stream onto channel: \n" +
                "   writer: " + this,
                e);
    }
}

How can i develop a getWritableChannel() method in order to write into a BLOB field inside a Database DataTable (RBDMS). I'd like to use Spring if is necessary. Thanks