Easy Rules Integration¶

The Easy Rules Project provides a simple, lightweight Rule Engine written in Java. Eclipse sensiNact offers support for integrating Easy Rules with the Rules Whiteboard

The easy-rules.osgi Module¶

The latest version of Easy Rules does not provide an OSGi bundle packaging, so it is necessary for Eclipse sensiNact to repackage the core library as an OSGi bundle. This bundle exports the three main packages provided by easy-rules-core:

org.jeasy.rules.annotation;version=“4.1”
org.jeasy.rules.api;version=“4.1”
org.jeasy.rules.core;version=“4.1”;uses:=“org.jeasy.rules.api”

Easy Rules Helpers¶

In addition to the core Rule Engine implementation the easy-rules.osgi bundle provides helper classes for building a RuleDefinition from a set of Rule instances, and for turning a List<ProviderSnapshot> into a Facts object suitable for rule execution

The easy-rules.config Module¶

The easy-rules.config module extends the integration provided by easy-rules.osgi by allowing Easy Rules based RuleDefinition objects to be created purely using configuration.

Configuration properties¶

Rules can be created using factory configurations with a factory PID of sensinact.rules.easyrules and the following properties:

sensinact.rule.name - the name of the rule
resource.selectors - A String+ property containing one or more JSON serialized Resource Selectors, which will be combined in an OR semantic.
rule.definitions - A String+ property containing one or more JSON serialized Rules

The Rule Defnition schema is as follows:

{
  "name": "Rule Name",
  "description": "Rule Description",
  "condition": "JEXL expression returning a boolean",
  "action": [
    "JEXL script performing an action",
    "Another action script"
  ],
  "priority": 7
}

JEXL execution¶

The JEXL condition and JEXL actions have access to the following context properties:

{
  "$updater": "Resource Updater instance",
  "$providers", ["providerA", "providerB"],
  "$data": {
    "providerA": {
      "$services": ["serviceA", "serviceB"],
      "serviceA": {
        "$resources": ["foo", "bar"],
        "foo": {
          "$set": true,
          "$value": 5
          "$timestamp": "2024-01-01T00:00:00.000Z",
          "metadata1": "ping",
          "metadata2": "pong"
        },
        "bar": {
          "$set": false,
          "metadata1": "pingpong",
        }
      },
      "serviceB": { ... }
    },
    "providerB": { ... }
  }
}

These values can be used when determining whether the Rule has been satisified, and when calculating an appropriate action.