creating a simple rule engine in java

Question

I am exploring different ways to create a simple business rule engine in Java. I need to present the client with a simple webapp that lets him configure a bunch of rules. A

Answer 1

A simple rule engine can be build upon closures, i.e in Groovy:

def sendToOutPatient = { ... };

def sendToInPatient = { ... };

def patientRule = { PATIENT_TYPE ->
    {'A': sendToOutPatient,
     'B': sendToInPatient}.get(PATIENT_TYPE)
}

static main(){
    (patientRule('A'))()
}

You could define your rules as closures, reuse/reassign them or even build a DSL over them.

And Groovy can be easily embedded into Java, example:

GroovyShell shell = new GroovyShell(binding);
binding.setVariable("foo", "World");
System.out.println(shell.evaluate("println 'Hello ${foo}!';));