Wednesday, August 24, 2016

Replaying Events in An Axon Framework Based Application

This post, shows how to replay events from the event store, in an event sourced application built with Axon Framework.

Note: This post applies only to 2.x versions of the Axon Framework, as the implementation of the event processing aspects of the Axon changes significantly with the version 3 release.

If you are not familiar with CQRS and/or the Axon Framework, then consider starting off by reading Exploring CQRS Architecture with Axon Framework, which is a series of post that explores the CQRS architecture/pattern and how the Axon Framework can be used to build applications according to the stipulations of CQRS.

If you’ve read these series of posts, or you are already familiar with CQRS/Axon Framework, then feel free to continue with the rest of this post.

Monday, June 27, 2016

Understanding Implicits in Scala

I knew about the maxim: "Implicits are evil" way before I started learning and using Scala. So by the time I started running into them in codebases, I was already biased. It was thus easier to raise my hands in despair at the "magic" that is implicit and just condemn their existence.

Obviously such a view is not healthy. So I decided to do what any sane human would do: If I am going to continually bitch about something, I should at least know some one or two things about what I am bitching about.

This post captures my understanding of how implicits work in Scala thus far. Not in the sense of how they work at the compiler or implementation level, but how they work in the sense of what they do and how to reason about them when encountered in a codebase.

It is not about when to make the decision to use or not use implicits. Or how to use them "tastefully". My current level of mastery of the Scala language does not permit me to make such pontification. Hopefully in the nearest feature, a post like this would follow.

Should in case you were like me a couple of months back, and just want a clue about what the hell is the magic going on with implicit, then you will find this post useful.

So let us get right to it.

Friday, April 29, 2016

Difference Between Value, Factory, and Service in AngularJs

There are various ways to create Objects in JavaScript. A couple include:

Using Object literal notation: Reference

var carObj = {
  model: "Mercedes-Benz CLS Coupé",
  getModel: function() {
  return this.model;

console.log(carObj.getModel()); // prints Mercedes-Benz CLS Coupé

Monday, April 25, 2016

Exploring CQRS with Axon Framework: Closing thoughts

...and this post, is the final one, in the series of posts on Exploring CQRS with Axon Framework. It is a summary of my thoughts on CQRS as a pattern and the Axon framework as a tool used in achieving this pattern. If per chance you have not read the other posts in the series, I will recommend starting from the very first post: Exploring CQRS Architecture with Axon Framework: Introduction

That said, I proceed into the details of this post.

Saturday, January 23, 2016

Exploring CQRS with Axon Framework: Overview of the Testing infrastructure

After a long break, I am finally getting around to picking up on the series: exploring CQRS with Axon Framwork. This post, which is on testing, is one of the two remaining posts left to wrap up the series. The aim is to follow it up, as quickly as possible, with the concluding post.

If you have not been following the series, I would advice to give the other posts a read before continuing with this post. You can start here: Exploring CQRS Architecture with Axon Framework: Introduction

As already mentioned, this post looks at the infrastructure the Axon Framework provides for testing. Just like the other posts in the series, it is accompanied by the exploringCQRSwithAxon project on Github. The Application is a trivial one, meant to further illustrates the content of the posts.

Thursday, October 29, 2015

Exploring CQRS with Axon Framework: Applying Event Sourcing

This post is part of the series of post on exploring CQRS architecture using Axon Framework. It looks into combining event sourcing within CQRS using Axon Framework.

The previous posts in this series has explored the various components of a CQRS application and in Introducing Domain Events and Event Handling, we are able to put everything together. We did all that without bringing in event sourcing, showing that it is possible to have a CQRS architecture easily without introducing event sourcing. But in this post, we do just that: introduce event sourcing.

There is a project on Github (exploringCQRSwithAxon) that accompanies these series of posts. It is a trivial application where we can perform debiting, crediting and transferring of money between two dummy accounts. The code in the project is meant to help illustrate the application of the Axon framework to building CQRS application.

Saturday, October 17, 2015

Exploring CQRS with Axon Framework: Introducing Domain Events and Event Handling

This is a post in a series of posts that explores the CQRS architecture with Axon Framework. It is recommended to read the previous posts in this series before going ahead with this one, as that would help in forming a thread of continuity around the topic being discussed. You can start from Exploring CQRS Architecture with Axon Framework: Introduction

There is a Github project (exploringCQRSwithAxon) that contains a simple application that accompanies the posts in this series. it is an illustrative application that allows debiting, crediting and transferring money between two fictitious accounts. It is obvious a trivial application, which is on purpose. It’s aim is not to capture any complex domain but to help illustrates the various components of a CQRS architecture and how the Axon Framework can be used to build these various components.