You can add calculation logic to ONEWEB Smart Forms using JavaScript & Manual Java Class. ONEWEB Smart Forms have Entity Actions to attach a JavaScript file to an entity. Please refer to Entity Actions section for more details on how to attach JavaScript to an entity.
JavaScript alone can be used for very simple calculations. But ONEWEB provides the ability to execute a Manual Java class through AJAX calls.
The Manual Java class needs to implement the ManualInterface and override the processManual method as shown below.