You should be able to use the ByteBuffer directly with the Java driver.
See the example on http://ac31004.blogspot.com.au/2014/03/saving-image-in-cassandra-blob-field.html:
ByteBuffer buffer =ByteBuffer.wrap(b);
....
// image is of type blob
PreparedStatement ps = session.prepare("insert into Messages (image, user, interaction_time,imagelength) values(?,?,?,?)");
BoundStatement boundStatement = new BoundStatement(ps);
session.execute(boundStatement.bind(buffer, "Andy", convertor.getTimeUUID(),length));
See they directly bind the ByteBuffer to the blob-type parameter in the prepared statement.