How to do a legacy software migration : a successful checklist

Legacy Software migration

Here is a small checklist about how to migrate a legacy migration and to ensure its success.

This article is part of my work to explain my knowledge about Software migration in the company Byoskill.

First measure your project according the changes involved by the migration :

  • The organizational changes
  • The process changes
  • The technological changes

The organization

You will have to think about each person involved in the Software that is going to be migrated. Which skills are required to develop, test, maintain, support the Software. How will you manage the brutal disrupt in their daily work and motivate them to embrace the change ?

I recommend you to have a clear picture of the team and not underestimate the needs of training, evangelize, and change management.

Changing technologies or framework, even without any feature changes may impact severely your end-users, the support and maintenance teams and the integration engineers.

The processes

An automated migration differs from a classical IT Software project by adding a certain disruption in terms of time and practices. Since the migration has to be hastened (thanks to the usage of specialized tools), the success of the project requires a high level of software development practices. Usually, the legacy software are still hitting the wall in terms of agility, silo breakup, continuous integration, test automation practices.

The legacy project migration requires to have a clear state (and view) of the following processes :

  • SDLC : Software development lifecycle.
    • What is the current process ?
    • Is their any traps or caveheats to be aware of ?
    • How much time does it take to push a new feature from the specification to the production ?
  • Test automation : You will have to answer many questions who are associated to well identified risks.
    • How the application is tested ?
    • At which levels ?
    • Are the tests automated ?
    • What is the coverage (estimated and measure) ?
    • What are the requirements to set up a new test environment ?
    • How much does it cost ?
    • Is test data available ?
    • How accurate is the test data ?
    • Which tools are required to execute the tests ? The licences
    • What would it take to obtain a sufficient coverage for the migration project ?
  • Continuous Integration : 
    • How the software is built ?
    • How much time does it take to produce a new release ?
    • What are the steps ?
    • Which parts are tricky or manual ?
    • What are the components to be built ?
    • How many individual parts composes the software ?
    • Which tools are used ?
    • What would it take to obtain a complete CI/CD  for the migration project ?
  • DevOps : 
    • Logging and Monitoring support :
      • Will the tools still compatible are the migration ?
    • Automatic deployment
      • What are the changes required to maintain (or obtain) an automatic deployment of the solution
    • Error and Exception handling
      • Detect and document any regressions in the current way to catch and handle the errors during the run
    • Performance testing
      • Does the software have any automated performance tests ?
      • Will they still be compatible ?
  • Release Management :
    • How many active versions for this Software ?
    • What is the branch release model ?
    • Versions to maintain and port
    • Frequency of releases and year schedule / roadmap

The technologies

A good legacy migration project is preparing a clear state of the perimeter to be migrated and the targeted solution.

It comes in a phase of three steps.

  • The actual picture
  • The definition of the target
  • The migration in itself

Drawing the current picture

The initial software assessment does really mater. Indeed an solution architect will detect any caveats and flaws in the current architecture that may critically slowdown the migration project.

Such assessment usually requires :

  • a technology survey : which technologies are used in the software, licenses issues, exact version and possibility of upgrade
  • an architecture assessment : will be controlled in priority the physical organization of the project (folders, files), the logical structure (components, package, functional and technical layers) and the dependency matrix (cycles, code weaving, code smells)
  • an automated test assessment : code coverage, tests documentation, test robustness/fragility, main complex components and their level of testing.
  • a code quality assesment : a quick review to identify in priority the main risks (reliability, security, maintainability)

The definition phase

This phase has four objectives :

  • Get a understanding of the cost and time of the migration project
  • Evaluate with the customer, the ROI of the operation
  • Eliminate the main technical  / functional risks of the migration
  • Communicate to the customer, the organization and process changes to be operated.

To achieve that, a main document (or specification) has to be produced, the migration guide.

This migration guide will expose the targeted solution, the way to achieve it, the necessary steps, a risk analysis and RACI, the cost and estimation of each tasks.

This definition phase may be accompanied by a Proof Of Concept(POC), a short term development performed on the current solution to assess the feasibility of the targeted solution and to allow any necessary test to be executed. It will be critical to pay attention to any functional regressions and performance regressions in this POC.

The migration

The migration is not a Big Rewrite. 

It’s an incremental, well-defined process where the automation is removing the main source of failure of migration projects : the time of execution.

Indeed longer the migration process is taking, more dangerous will become the project, debated and finally rejected.

A good migration project usually has the following qualities :

  • Incremental : in some way it’s possible to have the two technological environments living as room mates in the Software
  • Fast : The amount of rewriting, manual fixes and iterations to obtain the targeted solution have to be small.
  • Cost effective : The volume of manual operation cost should be significantly be smaller thanks to the automation
  • Critical : No legacy migration finds its justification without a real concern (Security, Investment, Scale up operation, Business loss or expectations)

Using S3 libraries with Minio mock server

Minio WebUI

In the continuation of my previous S3 article,

I present you, how to write a S3 Java Sample program that is using a mock S3 server to develop the functionalities.

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Java developer testing toolbox

JBehave : code

An article dealing with Java application and testing frameworks and related libraries. Continue Reading


How to implement CQRS with Spring : new framework

This article is a presentation of a new little framework, I have developed and used on several projects.

The framework is for Spring Framework and requires Java 8.0. The code is on GitHub and downloadable from Bintray or JCenter.

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Sonar plugins for AngularJS and Javascript you may not know

In this article, I will present you two new Sonar plugins that you will never find on SonarQube (for some good reasons).

Keep reading if you are developing in TypeScript, AngularJS 2, Javascript.

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My weekly DZone”s digest #1

This is my first post that offers a digest from a selection of DZone’s articles. I will pick DZone’s article based on my interests.

This week the subjects are : BDD Testing, Bad code, Database Connection Pooling, Kotlin, Enterprise Architecture

A few benefits you get by doing BDD

A few benefits you get by doing BDD : This article is an introduction to the Behaviour Driven Development practice. It’s interesting because we are regularly meeting teams, developers, architectures (pick your favorite one) that are confusing technical details and functionalities. As a result, the design, the tests and the architecture hides the user behaviour (the use cases ?) under a pile of technical stones. This article is a nice introduction. I recommend to go further these articles : * Your boss won’t appreciate tdd, try BDD * BDD Programming Frameworks * Java Framework JBehave.

Gumption Traps: Bad Code

Bad code, how my code...

Bad code, how my code…

Gumption Traps: Bad Code : an article about the bad code and how to deal with it.

{% blockquote Grzegorz Ziemoński%} The first step to avoid the bad code trap is to stop producing such code yourself. When faced with existing bad code,one must work smart to maintain motivation. {% endblockquote %}

This is a good introduction sentence. This week, I had a meeting with a skilled and amazing team. The meeting’s goal was to find a way to find the technical debt. The very technical debt that is ruining the application and undermining the team’s motivation. What I found interesting and refreshing in this article, is the pragmatic tone and the advice.

{% blockquote Grzegorz Ziemoński%} To avoid bad code, try to minimize the amount of newly produced bad code. {% endblockquote %}

How to avoid the depress linked to the bad code ? First of all, I want to say that developers are not receiving enough training on how to improve the code. Usually university / college courses are dedicated about How to use a framework. Therefore, few of them are able to qualify what is a bad code, what are its characteristics and de facto the ways to improve it. To avoid bad code, I try to demonstrate the personal benefits for the developers to improve their skills. Quality is not only a question of money (how much the customer is paying) but rather how much your company is paying attention to your training and personal development.

A lot of developers are overwhelmed under the technical debts without the appropriate tools (mind, technics, theory) to handle it. I try to give them gumptions about the benefits to be a better developer and how to handle the weakness of a sick application. To save a software rather than practicing euthanasia 🙂

Database Connection Pooling in Java With HikariCP

When we are discussing about Database connection pooling, most of my colleagues are relying on the good old Tomcat dbcp. However there is a niche, really funny and interesting, the guys that a competing for the best DBCP. And HikariCP is clearly a step ahead of everyone.

The article Database Connection Pooling in Java With HikariCP is presenting how to use a custom DBCP in your software.

Hikari Performance

Hikari Performance

I think it would have been great to present the differences with the standard DBCP and further debate on the advantages/disadvantages of the solutions. A good idea for a newt article 🙂

Concurrency: Java Futures and Kotlin Coroutines

Java Futures and Kotlin Coroutines An interesting article about how Java Futures and Kotlin co-routines can coexists. Honestly I am a little bit disappointed and thought that Kotlin would make things easier like in Node.JS

Are Code Rules Meant to Be Broken?

Another article about Code Quality and we could be dubious whether exists an answer to that question : Are Code Rules Meant to Be Broken.

I won’t enter too much in the details, the author’s point of view seems to be Code Rules are good if they are respected. If they are broken, it implies that the Code rules need to evolve 🙂 What do you think about it ?

Java vs. Kotlin: First Impressions Using Kotlin for a Commercial Android Project

This article is interesting since it presents a feedback session on using Kotlin in a Android project.

The following big PLUS to use Kotlin are :

  • Null safety through nullable and non-nullable types, safe calls, and safe casts.
  • Extension functions.
  • Higher-order functions / lambda expressions.
  • Data classes.
  • Immutability.
  • Coroutines (added on Kotlin 1.1).
  • Type aliases (added on Kotlin 1.1).

  Quality Code Is Loosely Coupled

Quality Code Is Loosely Coupled

This article is explaining one of the most dangerous side of coding : Coupling. Must to read article despite the lack of schemas.

Five Habits That Help Code Quality

This article is a great introduction on code assessment. These five habits are indeed things to track in your software code as a sign of decay and code sickness.

The habits are : – Write (Useful) Unit Tests – Keep Coupling to a Minimum – Be Mindful of the Principle of Least Astonishment – Minimize Cyclomatic Complexity – Get Names Right

10 Good Excuses for Not Reusing Enterprise Code

This article is really useful in the context of Digital Transformation to assess which softwares you should keep and throw.

Example of excuses : – I didn’t know that code existed. – I don’t know what that code does. – I don’t know how to use that code. – That code is not packaged in a reusable manner.

Test proven design

An interesting article and example on how to improve your own code using different skills. I really recommend to read this article and the next future ones : Test proven design.


I have tried Vue.js and I love it

Vue.js Framework

I have tried Vue.js and just love it.

Some weeks ago, I started a new project for which, I have to build an internet website.


After spending really long hours on internet, browsing, collecting every possible testimonials and advices and comparing them to my first impressions, I decided to start with an hybrid / multiple page site.

(if you are interested by the reasons, it will be the subject of another post).

An hybrid /multiple page site is a website where the content is rendered both from server side and client side at the opposition of single page application (SPA) full client side and a classical server side site(PHP..) Since I want to use the power of modern Js Frameworks as double binding, refreshing, Ajax widgets, Es2016, reactive programming and somewhat control which pages needs to be reloaded, I had to make a choice.

The list of choice is somewhat limited if keep only the 5 most popular ones. (yes I am resolutely not a pioneer of the JavaScript Jungle)

The framework selection

I made the following list :

  • Angular 2+ (they are increasing the major version number for each patch 😅)
  • React.js
  • AngularJS
  • Ember. Js
  • Vue.js
  • JQuery (it is a joke)

Selection criteria

I defined some selection criteria besides the popularity :

No code bloat : specifically to JavaScript, the syntax and the missing OOP native programming have been producing many frameworks with dumb syntax without any semantical and often syntaxical meaning. To overcome the limitations, many frameworks are using syntax sugar, making them a nightmare to memorize. The most ridiculous is the attempt to stick on these syntaxical blobs, some pseudo theorical terms.

A good framework should offer different levels of usages from the straightforward approach to build quickly and easily a website with the common use cases to the low-level approach where the experimented developer is able to tune the required details. What has been done in Laravel, Spring framework or Symphony are good samples.

Symphony framework is known as a huge galaxy. Many components, industry quality grade, but an overwhelming complexity if you start head on.

Therefore they have created a micro — framework called Silex to bootstrap an PHP application without the nasty details and it is deadly simple. If you want more complex things, the components behind Silex are the Symphony ones.

For a web framework, always study how do they handle forms. Especially a basic post form. It takes five minutes in plain HTML to build an (unsecured) form. How long does it take with this framework?

The same thing works for **Spring* and Spring boot.

The framework must have a business friendly licence. No doubt, no legal restriction for the future company. (by the way do you know you cannot build weapons software in Java, please stick to the line…)

An extensible / plug-ins architecture. I believe the success of a framework resides in the possibility to enable the necessary functionalities (aka feature toggling) during your project. Authentication, reactive programming, lazy loading, modularity.

The evaluation (aka trolling section)

Based on these selection criteria, here is my evaluation.

Disclaimer: I have a highly respect for the guys who wrote these frameworks and I do not doubt of their outstanding skills. AngularJS

I have experienced projects with AngularJS and I renounced since it is a deprecated technology. Too much code bloat, slow (I should rather say hard-to-tune) and all efforts are concentrated on the new Angular framework. Also, I think I could have a problem with my use case and disabling the AngularJS router.

Angular 2

Angular 2: I have received a training in January and wrote several prototypes since. I have been a huge fan of typescript, angular-cli. I was happy and thinking, they took the best ideas from the other frameworks and build a big melting pot.

Angular : melting pot

In Angular, you will find web components, uses template a la React.js, you have opt-in double binding, directives, modular architecture, lazy loading and so on and so on. But I progressively hate Angular for many details, slowing me down in my developments.

I really dislike their API and concepts to build forms. You have two choices, a template form design and programmatic form design. The first one is almost useless and the second one is deadly cumbersome.

In Angular, they decided to kill HTML and recreate it. How? Case-sensitive attributes and non HTML attributes. You cannot use your normal code editor on it. Beautifier tools not works or partially works. And worse of all, they conceive this awful syntax based on brackets, parens, Well, I think their are huge practitioners of the Brainfuck language.

Brainfuck language

Brainfuck language

The last issue I encountered is with their wish to produce an industrial, scalable (in the sense if I put more developers on my project, I maintain a stable learning and complexity curve). Yes, they provide dependency injection, IOC. But it really increases the learning curve.


I really wanted to start with React.js. As far I have studied it, the framework seems full of promises, with some nice pluggable functionalities.

However at the time I began to use it, I received a lot of news. The concern is about the React.js license, the Facebook license (link1, link2, link3).

Since there is a threat for the future business (everything can be considered as a social network after all), I have rejected it.


I have never tried Ember.js. Based in my readings, the framework is definitely worth of attention to build SPA applications but not for my use case. Note : during the writing of this post, I felt on that link, confirming that maybe I was wrong about ember.js


On Twitter, I am receiving a lot of feedback from happy users of Vue.js and I decided to give a try.

The syntax seems deadly simple.

Here is the brief of my experience :

I did not use vue-cli, I had to create my own packaging to adapt Vue.js to multipage architecture.

Code bloat: the Vue.js framework is really simple and the documentation quite good. The documentation for the plug-in vue-loader is quite good but I really hate the webpack syntax to enable it (rant..)

Learning curve: I did not try the most hard-core functionalities of Vue.js, though I am using vue-loader, a different template renderer (pug), transitions, a little bit components and lazy loading.

My biggest difficulty have been to maintain my js bundle as low as possible by producing chunks.

The second issue has been to understand why creating a view was creating an App and my component below using the render() function. However I think that Vue.js is easier than Angular. 2.

As in the previous example, the syntax is quite straightforward, no need to learn complex concepts to begin with.

The framework is also compatible with Typescript and the logic behind is quite simple.

Vue.js can be extended with several plug-ins and functionalities. I did not try all of them and the fact you are enabling them manually is comforting me in my approach.

Vue.js is not enforcing a particular programming paradigm(IOC, interfaces, Reactive programming, or. RxJS).

The only reproach I could formulate is a little fear about the Vue.js ecosystem. Please integrate existing libraries rather trying to recreate or mimic ReactJS libraries.

In conclusion, both of these frameworks are legitimate and have their lot of practitioners, and I don’t blame it. Vue.js has been my choice and I do not regret it, yet, since it has made my project easy, fun and effective.

I will try to provide more feedback in the following weeks especially on form editing, unkt testing and E2E testing.

Thanks for your attention


Codacy : an easy-to use code quality review solution

Some time ago, I organized a talk on “Code Quality and why developers should care about” for my company. In that presentation, I demonstrate some tools, unfamiliar for the audience : young developers and battle-hardened IT developers. One among these tools has brought to me a lot of questions : Codacy. I will present its features and perform a comparison between Codacy and SonarQube from SonarSource.

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