For one of my project, I needed a simple rules engine.

I like the DecisionDag that Mandar Jog built. It uses Commons JEXL and allows rules to be defined in plain english.

In my use case, I had following goals.

• keep it simple (KISS)
• rules engine as micro-service (deployable to cloud).
• a rules catalog of sorts that allowed new versions of the rules to be added and older ones removed.
• ability to calculate within the rule and return results.

This is a simple rules engine built with spring-boot in java.

The rules are in plain javascript.

Nashorn sccript engine allows runtime loading and evaluation of rules.

• Install the app by cloning the repository rulesengine

• Build and run the app

     $ cd rulesengine
     $ gradlew bootRun
  

• Call rest end-points.

     $ curl -v 'http://localhost:8080/api/rules/WhatToDo?family_visiting=yes'
     
     $ curl 'http://localhost:8080/api/rules/WhatToDo?family_visiting=no&money=poor&weather=good'
     
     $ curl 'http://localhost:8080/api/rules/WhatToDo?family_visiting=no&money=poor&weather=cold'
     
     $ curl 'http://localhost:8080/api/rules/WhatToDo?family_visiting=no&money=rich&weather=cold'
  
  

Meet PCF Dev. It is a simplifed, and minimized version of the Pivotal Cloud Foundry intended for your local machine. And Getting started is simple.

#####Deploy to cloud

• Target the cloud instance

     $ cf login -a api.local.pcfdev.io --skip-ssl-validation
  
     API endpoint:  api.local.pcfdev.io   
     Email>     admin
     Password>  admin
  
  

• Build and deploy to cloud

     $ cd rulesengine
     $ ./gradlew assemble
     $ cf push -f manifest.xml
  

• Test the cloud service

     $ curl -v 'http://simplerules.local.pcfdev.io/api/rules/WhatToDo?family_visiting=yes'
     
     $ curl 'http://simplerules.local.pcfdev.io/api/rules/WhatToDo?family_visiting=no&money=poor&weather=good'
     
     $ curl 'http://simplerules.local.pcfdev.io/api/rules/WhatToDo?family_visiting=no&money=poor&weather=cold'
     
     $ curl 'http://simplerules.local.pcfdev.io/api/rules/WhatToDo?family_visiting=no&money=rich&weather=cold'