This is an internal documentation. There is a good chance you’re looking for something else. See Disclaimer.


Drools is a rule engine which we use in Nice2 to implement customer logic. Unlike logic implemented in Java which can only be written by our developers, we have the possibility to let anyone write these rules in a running system.

A rule always consist of two parts, the when and then section. The when part is used to check for so called facts. The existence of facts or their contents can be checked, but no code can be executed, it only checks state. That’s where the then part comes in. In there it’s possible to write Java code and interact with the facts found in the when part.

The entire documentation for our version of Drools can be found here.