OH3RuleEngine for java

OH3RuleEngine is an pure JVM alternative to Openhab rules-dsl.

Why OH3RuleEngine rather than rule-dsl provided by openhab?

For most of the users rule-dsl would be enough, for more advanced users rule-dsl has some limits which does not exists when using OH3RuleEngine

Those limitations are:

• Pure IDE support for hand writing *.rules files
• No support for classes objects
• Limited code reuse

Requirements

• Java 11

Installation

TBD

Getting started

Connecting to Openhab

Connecting to your openhab is simple as it:

var client = new OpenhabClientImpl("http://192.168.0.132:8080", "login", "password");

new OpenhabRuleEngine(
client,
List.of(
    new TestRule()
)
).start().join();

How to write rules

OH3RuleEngine provides you two ways of creating rules

Classic Java object

static class TestRule extends Rule {

    @Override
    public String name(){
        return "Test";
    }
    @Override
    public Condition when() {
        return onStartup();
    }

    @Override
    public void run() {
        System.out.println("Foobar");
    }
}

Builder

rule("Test")
.when(onStartup())
.then(() -> {
    System.out.println("Foobar");
})

This approach is not recommended as it can lead to mess in the code.

Rule Examples

Terratium temperature controller

public class TerrariumTemperatureRule extends Rule {

    private final String currentTempItem;

    private final String targetTempItem;

    private final String heatingItem;

    public TerrariumTemperatureRule(String terrariumId) {
        this.currentTempItem = terrariumId+"_Actual_Temperature";
        this.targetTempItem = terrariumId+"_Target_Temperature";
        this.heatingItem = terrariumId+"_Heating";
    }

    @Override
    public Condition when() {
        return or(
                itemChanged(currentTempItem),
                itemChanged(targetTempItem),
                onStartup()
        );
    }

    @Override
    public void run() {
        if(getNumber(currentTempItem) > getNumber(targetTempItem)){
            setState(heatingItem, OFF);
        } else {
            setState(heatingItem, ON);
        }
    }
}

Condition Examples

Item changed

itemChanged("FOO");

Item changed to value

itemChangedTo("FOO", "12");
        
itemChanged("FOO").to("12");

Item changed to value of other item

itemChangedTo("FOO", item("BAR"));
        
itemChanged("FOO").to(item("BAR"));

Or/anyOf

anyOf(itemChanged("FOO"), itemChanged("BAR"));

or(itemChanged("FOO"), itemChanged("BAR"));

itemChanged("FOO").or(itemChanged("BAR"));

And/allOf

allOf(itemChanged("FOO"), itemChanged("BAR"));

and(itemChanged("FOO"), itemChanged("BAR"));

itemChanged("FOO").and(itemChanged("BAR"));

Cron

cron("* * * * * *"); // execute every second
cron("0 * * * * *"); // execute every minute

Roadmap

• Define items via code
• Define things via code
• Code to sitemap compilator