It is time to update our REST API so that it becomes an event-driven application. You will see that the changes we make are not difficult to apply. We will start by updating our dependencies so that Project Reactor classes are accessible. Open your API application build.gradle configuration and extend it:
...
dependencies {
...
compile 'io.projectreactor:reactor-bus:2.0.8.RELEASE'
...
}
...
Here, we introduced support for a Project Reactor bus. We will use it to trigger an action in some particular situations. We will email the system administrator if the number of total Notes or TODOs in the system reaches a critical level. This example is trivial. One good example would be triggering actions when storage reaches a significant number of sold items. Another could be if the number of unsubscribed users increases more than a...
