Plugins

FactCast Server UI is extensible using Plugins. Those plugins can be handy for enriching the plain fact information you see.

Scenario

Consider you have the following Events:

• UserRegistered
• UserLogin

where UserRegistered has a UserId and a UserName, and UserLogin is emitted after a succesful login, having just the UserId.

Now, when you look at UserLogin Events through the UI, the UserId is all you see, because thats all the json there is to your fact payload. However it might be nice to know the UserName for a UserId when you look at it. Also it would be cool, to ‘annotate’ the Json with that information. This can be done by building custom Plugins.

A plugin provides you an API to inspect and annotate the Json that will be displayed to the User. As part of a plugin, you could for instance build a projection that consumes all the UserRegistered Events to provide a queryable Map<UserId, UserName>, and use this data to annotate the UserName to every UserId.

Getting started

Take a look at HeaderMetaTimestampToDatePlugin as an example of the simplest Plugin possible. It just turns the meta._ts attribute of the fact header into a human readable DateTime.