Today we are going to talk about one of the most infamous mechanisms of the notification server: StateDrivenEntity. Recall that every notification server can be thought of a gearbox, consisting of components which can be thought as the drive wheels. When our application launches, our notification server is at first not running. We need to perform some action in order to make it start, similarly to how we need to insert an ignition key and turn it in order to start a car engine.

This is not really part 3, but a correction to the design of the fractal processing server sample. Currently, the design we use is the one in the following picture: I remind you that the component PixelStoreLogic receives events from the RequestListener and events from the ColorConvertLogic. The events from the RequestListener tell our logic to store the pixels received from the ColorConvertLogic. Once PixelStoreLogic receives all colored pixels of the image, it publishes an event containing all these pixels, and also cleans these events from its storage.

Last time we saw how an implementation of a server over the notification server framework looks like. We discussed code of events, logics and rules. Something we have not discussed yet is how do we link components to one another. This is something that is resolved via a mechanism called component builder. The component builder is an interface provided by the notification server framework, where one defines the components of a specific server and defines the links between these components.

Today we are going to show a partial implementation of the fractal processing example we described last time. This should give a feeling of how typical code written above the notification server framework looks like. We skip the RequestListener implementation for now. We will get to it in another time. What is important though is the event that the RequestListener produces. As explained in the first post, events are messages that flow through the server’s components.

Today I want to discuss a simple example for a notification server, which is often given as a first exercise for developers new to the framework. This will be a variation of the usual exercise, so I can demonstrate some of the core concepts. The notification server we want to implement today is a server that generates pictures of fractals. For those of you who are not familiar with fractals, these are mathematical shapes with self-symmetry.