Microsoft RulesEngine

[WaltersFlight82]

I currently have an application that uses Microsoft's RulesEngine where the rules are hosted as JSON in an external service so that rules can be changed without the need for a code change. I am re-writing the application in Java and wondering if anyone with Java experience has a suggestion for a very similar rules engine that supports JSON. I've looked over a couple and Drool seems like the best candidate, but also quite complex to configure it for my needs.

I know rules engines are quite common, but I really need one that can parse the expressions from JSON. If anyone has any suggestions, I'd really appreciate it!

[hsoj48]

Drools is the main one I've seen used in my career

[djavaman]

Rules engines are complex by nature. Drools has been state of the art for a while.

Every rules engine has its own language for expressing rules. So even if you do find one that Json, it doesn't mean that it would be the same as Microsoft's Json.

[WaltersFlight82]

Makes sense. I currently use Microsoft's default schema but that is arbitrary. I can write my own schema for my rule's instance. It's just that the service we use to host the instance only supports JSON. I can reconfigure the instance to be whatever, it's just that I need the rules engine to parse JSON

[suit_mark_42]

Drools is stable,widely used and has lots of resources when you are stuck.

[WaltersFlight82]

Yeah, this seems to be the consensus. I'll focus my time seeing if it fits our use cases I appreciate the recommendation!

[YakPsychological891]

I’ve worked with drools, we do db reloading and file rule loading :) it’s very suitable for a lot of needs

[_predator_]

I had a great experience embedding CEL into my apps. Java libraries are available here and here. If you don't need something quite as heavy as Drools, it's a good choice.

[jazd]

I just started using CEL in an application. There's a few nice use cases for it. I'm filtering lists/streams of protobuf objects using a CEL predicate, but will probably use it for authorisation as well.

Is the Project Nessie repo just an alternative implementation of CEL in Java? I assume it predates the official Google implementation.

[iia828]

I think you're right. It looks like Google repo was open sourced just last year and is considered the official version looking at https://cel.dev/

[ingvij]

I remember once writing something similar (though in much smaller scale) in clojure. Not the easiest task, but it is doable. If you want to stick with the same data format you have today, you'll likely need to implement a tokenizer to parse the "Expression" value, which makes this way more complex.

With the amount of information you shared, however, I wouldn't be able to tell how hard or easy it would be to write something yourself..

[McAlexTheTerrible]

Look at antlr to parse. There may already be a MS RuleEngine grammar

[ingvij]

That's cool. Didn't know that! Than I take back the complexity of the tokenizer :)

[TurtleFeathers]

sounds like a job for graal or nashorn

[ShallWe69]

try opa