Code lines of Nokia’s Open EMS Suite were very much in my life during summer 2006. During the time, my ex-boss Mr. Olli-Pekka Kallasvuo (OPK) was building the big picture of the company as I was the one writing code lines in Karaportti, Espoo.

Yesterday, many Finnish citizens and reporters of Yellow Press were enjoying a weird Finnish tradition when last year's tax information was again published. That information reveals how much every citizen earned last year and in this cold country some of us warm themselves up by reading how much money did their neighbours get last year.

Halloween is over and it is again time to get into serious business - welcome to Software Design Principles part 3: "Tell, Do NOT Ask".

Our small software team is soon finishing an integration project where a new web-based system has been developed and integrated to work with the registry and sales management systems in the client's old environment. Prior to this project, I was dealing mostly with web and enterprise system projects, but I must admit that this past experience did not help me as much as I thought. Now as the project is about to be ready, some conclusions can be drawn up to help in the planning of similar projects in the future.

Software Design Principles #2: OCP. "Software entities should be open for extension, but closed for modification." This one has the obvious benefit where the underlying code will not need changes when new methods are being created.

One key feature of Object Oriented Design are the Interfaces, that help us to have multiple implementations for a single Interface. The idea of OCP is to create abstract interfaces instead of classes, making the adding of new behaviour as easy as creating new classes - without touching and breaking the existing code.

package com.jippii.servlet.video;

import java.io.*;
import java.lang.*;
import java.util.*;
import java.sql.*;
import java.security.*;
import javax.servlet.*;
import javax.servlet.http.*;
import freemarker.template.*;
import com.wrox.util.LogWriter;
import com.wrox.connectionpool.*;
import com.jippii.util.MultiPartInputStream.*;

// Markus Virtanen (c) 2001
// wirtanen@nic.fi
// Jippii Group Oyj

public class VideoServlet extends HttpServlet {