Multilayer architecture

For some time I am thinking about application architecture. Consider pros and cons and tried to redesign the concepts of how to develop an application that the architecture uses. However, after gathering more and more information I came to one simple conclusion: I try to invent a circle again, which I don’t really want to. Many web systems work in multi-layered architecture. What does that really mean? What is it and what is it? Regardless of whether we are building an internet portal, booking system, document circulation system in the company, electronic banking is a part of the elements remains very similar but never identical.

Why do we really need the architecture of the IT system? It is often the case that when the complexity of IT system increase, an appearance of additional components caused a need for their separation, a possibility of easy change to another component. This solution forced the use of specific protocols, declarations of abstract classes, or direct reference to fields and class methods.

Single-layer architecture
Usually, it is a single application that does not require any external communication to perform tasks.

Double layer architecture

Client – Server or Master – Slave. These are usually two programs located on one machine or scattered geographically. The service provider is a superior program and one or more programs use these services, for example, a web server, an email server, an application server.

Multilayer architecture

This model consists of more than two layers. Separation of the user interface, storage of data into several separate layers that can be separately developed and scaled. Such a division facilitates their maintenance and mutual development does not affect the other layers.


Description of specific elements in the layer:

  • Frontend
    • Unser Interface – implements the logic of handling the presentation layer for the user
    • Gateway – induces and  provides services to external systems
    • Admin Interface – implements logic for handling the presentation layer for the administrator
  • Backend
    • Message-service(Commons) – it supports common logic
    • Scheduler – responsible for periodically running processes
    • Security Management – permissions and authentication management
    • Process Managment – allows to running long-term processes with the need to maintain and interact with the user
    • Domain Specific Components – responsible for fixing and accessing objects
  • Database – relational database

Advantages and disadvantages of layered architecture:


  • I don’t need a specific technology or vendor platform to create multi-layer architecture
  • Testability – Is very easy to create tests in automated testing environment as JUnit for example, for each layer
  • Separation of layers permits to easily map functional requirement with system modules
  • Enhanced Security
  • Layered architecture enables to update only the application servers, not all clients in case that we want to modify only business logic
  • Hidden database structure


  • Communication that can be complex
  • Performance and it’s required to use additional tools for measure and reporting this information
  • Difficult to implement and maintain

That’s why I decided that Energy Billing System will be based on a multi-layered architecture. There is one more aspect, I will be creating applications for the first time based on this architecture, so I will make a lot of mistakes, which is very good. Why? Because I will be able to solve them later.


What is Docker?

Docker is a tool designed to make it easier to create, deploy, and run applications by using containers. Containers allow developers to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package.

Docker is something like a virtual machine, but Docker allows application use the same Linux kernel without unnecessary dependencies that may be on the host computer.  This allows for some performance and reduces the size of the application.

The huge advantage of Docker is that is open source. That means that anyone can contribute as a volunteer too.

Who is Docker for?

Docker is a tool that’s designed for developers, administrators and software testers. For developers, it means that they can focus on writing code not maintain the environment. Reduce the number of dependencies, and also quick start with setting up initial development. Administrators get flexible and fast way to create and get running environments on easy way.  Software testers get the same environment that developer get to write feature. The last part is very important for two points: there is no misunderstanding in environment dependencies, and if there is a bug in software is easy to track and reproduce as well.

Getting started

On the Internet, there are a lot of information about Docker and why is so sexy thous days. Beginners guides for Docker, command-link simulators, a lot of images that are ready to use.  But I want to create my own tutorial that will be available on youtube channel. Starting with some basics to some advanced setup as well.

Docker and security

As a lot of tools, Docker brings some security too for the applications that are running in this environment, however, containers are not the thing that we can speak about security.  For example, there is something like kernel exploits, DDOS attacks, breakouts, poisoned images and secrets that can be compromised.


Maven #03 ~ How to create Maven project in IntelliJ

To create a maven project using IntelliJ we can to import: pom.xml file or create a project from scratch.
This post describes how to use this second option.

First, we must to open Wizard and select: Create New Project

From next window select: maven and after that mark: Create from archetype

On the same wizard window select: org.jetbrains.idea.maven.model.maven-archetype-quickstart

On the next window view type GroupId and ArtifactId:

Select Maven home directory:

The last but not least, insert location directory of your project:

The last step is to click Finish button to create a project.

Maven #02 ~ pom.xml

pom.xml is the main element of our project. In file are defined all of the dependencies for example:

  • a way of building a project
  • testing
  • running a project
  • generating documentation
  • creating a release


After generating project pom.xml file looks as follows:

It looks very raw. Only groupId, artifactId, modelVersion, version. This information on this step is not very important for us. First, change that we will make will be adding JUnit library.

Now we can compile our project:

As we can see project build successfully. For now, we should look at three commands:

  • mvn  – this command runs maven and proper pom.xml file
  • clean – delete target catalog and old files version
  • compile – runs java compiler

Maven #01 ~ What is Maven?

Apache Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM), Maven can manage a project’s build, reporting, and documentation from a central piece of information.

Primarily used for Java-based projects but that can also be used to merge projects in other programming languages like C# and Ruby. Many integrated development environments provide plugins for Maven. Typical tasks if a build tool is a compilation of source code, running test and packaging results into jar files. Maven can also perform related activities, for example, creating websites, uploads build results or generate reports.

Automating process of creating the initial project structure for Java application is very important, especially when doing it manually may take much more time and also there is a possibility for making typos during using some commands in the console, the last one is very frequent.

A little bit history.
Originally Maven was designed to simplify building process in Jakarta Turbine project.

What for?
Maven can be used for:

  • handle dependencies and intermediate dependencies
  • easy selection of tasks from the command line
  • versioning and tagging code
  • a large number of plugins to simple and complex tasks
  • Integration with all IDE such as Eclipse, NetBeans or IntellyJ
  • ability to manage a number of the modules of the project at a time
  • support for:
    • unit tests
    • integration tests
    • load tests
    • performance tests
  • application builds
  • generating documentation
  • releases
  • mailing list management

Maven is working according to the Convention Over Configuration pattern, which means that the configuration requires only those components that are nonstandard or user will want to adopt them for their needs, and the same configuration change can also be found under only one file – pom.xml.
Developers can build Maven project without the need to understand how the individual plugin works.

I use several systems start from Linux, Windows and Mac OS X machines. For this post, I will use Mac OSX.
Open terminal and type: brew install maven

If we have already maven installed, in a terminal should appear:

After installing Maven should check if everything is working properly, this purpose should be in the command line to run Maven and check the versions of what was installed:

As you can see installation is not difficult in inches. Some different looks to install Maven on Linux and Windows.

Before we turn to the creation of the first project we need to discuss a matter of a few, namely what they are:

  • artefact
  • group
  • version

The artifact is a name that identifies the project in the group. The group allows you to organize the namespace in which it is the artifact.

Both the group and artifact and version uniquely identifies the library of which we want to use. There is also something like what is called a plugin and archetype. The plugin is a special Java language, class in which performs the appropriate actions on the basis of asking configuration, for example, to pack compiled class to a jar file, generate documentation. An artifact is a specific plugin using which created them st project. It contains in its structure mapping of tree directories a new project, or file pom.xml contains basic project data.

Generating project
To generate maven project we have two options. First from a console and second from IDE.
Creating maven project looks as follows:

With this command Maven generates a Java project:

This last step can take some time depends on how much RAM memory do you have (These days it’s 16 GB).
Structure of the genereted project looks like follows:

We have generated whole Maven project structure Java source code. Maven created class which is just simple “Hello World” program. We have also can see that is the simple test class. In root catalog, we can find our pom.xml file:

To compile Java source code we need to trigger: mvn compile in root project directory. This command runs through all life cycle phase, which is needed to compile a project.

To run test phases instead to run a full build we need just to trigger: mvn test

To clean project and remove all generated files from ./target directory we can use: mvn clean


  1. Apache Maven Project
  2. MVN Repository
  3. IntellyJ IDEA Maven
  4. Supported tags and respective Dockerfile links

  5. Jakarta Projekt

  6. Five things you didn’t know about Maven by IBM

  7. Introduction to Apache Maven 2

  8. Deployment of artifacts with FPT

  9. Maven Wrapper GitHub repo

Lv0. VIM user

In the beginning of this post, I asked myself: why Vim and why I would like to cut my fingers? (Joke). An answer to this question is simple: I met with a number of situations in my life where I  actually edit the file on the server or on a specific device connected to the network. But how to do it when there are no possibilities of installing any external text editor?

Everyone has their own toolbox, which is a set of tools that uses in everyday work and even after work. Sometimes it is so that incoming to the company/job anyone could ask a simple question. What tools do you use? So then what you say? In my opinion, either in the work of the tester, programmer or system administrator and any other work related to IT, it is important to know well and use a text editor. And the text editor in both Linux and Unix is Vim. Some will say that the Vi, but for simplicity, I will say that Vi and Vim mean to me almost the same thing.

For the moment someone says, but he is the best Emacs text editor, again, another person can say that Atom is really great. OK, I agree with all the views, but … There are some cons. Especially on any Linux and  UNIX machine. If I log onto the production machine likely I’m will not even have the right to install any additional software but use this one that is already available. Of course, we can look around and see what happens but it will be hard with installing there any additional software. However, we will not use such editors as, for example, nano the text editor is often used on Ubuntu, but Red Hat or CentOS no longer can be a pre-installed editor, which is relatively easy to use.

Vim is free. If we have one machine – our beloved laptop we don’t need to pay for the license. We have 10,000 servers – is still free on each of these machines, there are no hidden costs involved.

The third reason – Vim is super customizable. The ability to install plugins, write your own and the engine itself can not be compared with any paid tool.

Another important thing is that Vim does not require a graphical user interface. Most servers do not have a graphical user interface installed, the X server so inevitably we can not run anything that will allow you to display icons, Eclipse, or are other java-based editors. We can never assume what we have installed on the server.

The last reason: Vim is a fast tool for editing code or editing files. If you’ve ever seen a user who has for several years used the Vim and how he can make changes in the code you were a probably very impressed. There is a competition which aims to see how quickly the participants can do the right things in Vim.

There is one disadvantage, the learning curve but in the end, it is worth it.

Get Notice 2017

An interesting idea has been spread in polish software development world. Recently is called “Let them know you” (“Daj się poznać” in Polish). It’s all about developing an open-source project and blogging to share the knowledge about this. Last year I also participate in this event but from lack of a time, I didn’t finish my project. I hope that in this year I will be able to complete my project as I planned.

What this mean for me and especially for others?

For me, it’s a time to challenge myself with creating something to solve one simple problem. And for others make live easier. Another thing I would like to achieve is to return to writing. A few years ago when I was 17 years old I started with the first blog. It was not pretty much easy for me. So after a few posts, I closed my blog. Then I didn’t know the value od sharing of knowledge. Currently, I approach things a little different.

I don’t like to guess how much I will have to pay my bills in a given quartal or first/second half of the year. In the other hand, no one likes to pay bills. Especially high bills which nowadays it’s not easy. Please imagine that suddenly comes a high electric or consumed water bill. We don’t need to imagine because it usually is. So how to be prepared? How to reduce consumption? How to compare consumption with the previous billing periods?

A solution is an application that can allow users to check a status of used energy in each time. Compare how much energy has been consumed in each month.

I think that such an application can be helpful and will help solve one basic problem, namely notifies you of the charges on the present day user. Unfortunately, this is already on the side of us will lay what do we do with this information. Do you start to save and manage their resources wisely, or we will be wasteful.

In this project, I want to use Java, Spring, R language to data visualization and also python. Probably there will be the android application, but for now, I want to concentrate on core application.

2016 -retrospection

2016 it was a very strange year for me. A lot has happened at the turn of the year both: good and bad. I have met many great people, visit several countries, mainly in central and western Europe. I worked with many people of different characters and the approach to life.

Last year taught me a lot, showed what I’m doing well, and show me what I don’t really know.

I started programming in Ruby and Rails. Still coding at night.
Last year has passed me very quickly, and we have already 2017.

For the new year, I don’t really have any decisions. Some few goals that I want to achieve. Starting from a personal sphere, personal development and ending with a professional sphere.

2017 will be a good year. I assure you.

Hamming distance

Today’s post will be about hamming exercise. This exercise can be found on: First two task were very simple and I will not bother anybody with them but the hamming exercise was very nice to learn something new. About this exercise: … put in two lengths of DNA and calculate their hamming distance.
Following is the README file or basics instructions of the exercise:

Write a program that can calculate the Hamming difference between two DNA strands.

A mutation is simply a mistake that occurs during the creation or copying of a nucleic acid, in particular DNA. Because nucleic acids are
vital to cellular functions, mutations tend to cause a ripple effect throughout the cell. Although mutations are technically mistakes, a very
rare mutation may equip the cell with a beneficial attribute. In fact, the macro effects of evolution are attributable by the accumulated 
result of beneficial microscopic mutations over many generations.
The simplest and most common type of nucleic acid mutation is a point mutation, which replaces one base with another at a single nucleotide.

By counting the number of differences between two homologous DNA strands taken from different genomes with a common ancestor, 
we get a measure of the minimum number of point mutations that could have occurred on the evolutionary path between the two strands.

This is called the 'Hamming distance'.

It is found by comparing two DNA strands and counting how many of the nucleotides are different from their equivalent in the other string.

^ ^ ^  ^ ^    ^^

The Hamming distance between these two DNA strands is 7.

In my solution, first I split DNA strand into an array due to the each_shortest_strand method. But I realized that is a bad idea. In addition, iterating to the end of string1 and also ensuring that we were comparing to an existing base pair in string2.


100 Days of Code – second edition

In 2016/04/10 I start 100 days of code challenge. It was not easy and I almost have done it. Almost it means that one day stays without commit. But happy information is that 99 days was with at least one commit. I was a very busy time for me. I learn a lot, especially how to code in Python. But this one-day caused that this whole challenge it does not count. So from today I start again nex, the second edition 100 days of code challenge. Rules are the same.


As we can see in above picture there is the screenshot from my GitHub account from today.