User-defined Rules

Starting with version 0.5 of the Logic Module, users may define rules, which are saved in the database. The logic module has built-in support for writing rules in Groovy and Java, while other modules may add other languages by overriding the org.openmrs.logic.rule.definition.LanguageHandler interface.

Groovy Rules

When defining a Groovy rule, you are defining the contents of the rule's eval method. Precisely, the code you are writing is enclosed in 

import java.util.Map;
import org.openmrs.Patient;
import org.openmrs.logic.*;
import org.openmrs.logic.rule.*;
import org.openmrs.logic.result.*;

public class GENERATED-NAME extends AbstractRule {
    public Result eval(LogicContext context, Integer patientId, Map<String, Object> parameters) throws LogicException {
        YOUR-CONTENT-INSERTED-HERE
    }
}

You have access to all of Groovy's language features, including closures, so as a very contrived example you could do something like this:

def square = { x ->
    x * x
}

def myString = [2, 4, 6].collect { "${ it } squared is ${ square(it) }" }.join("\n")

return new Result(myString)

Java Rules

These "work", but are very hard to use. (Why not use Groovy instead? It's better...)

Your rule definition must be a complete Java class definition, in the package "org.openmrs.module.logic.rule" with the class name "CompiledRuleXYZ" where XYZ is the internal ID of the rule definition (which you can read from the url of the Edit Rule Definition page after "id=").

For example, the following would work (if it is the rule with id=3:

package org.openmrs.module.logic.rule;

import java.util.Map;
import org.openmrs.Patient;
import org.openmrs.logic.*;
import org.openmrs.logic.rule.*;
import org.openmrs.logic.result.*;

public class CompiledRule3 extends AbstractRule {
    public Result eval(LogicContext context, Integer patientId, Map<String, Object> parameters) {
        return new Result("I would recommend Groovy instead");
    }
}