Class RuleEngine


@Named @RequestScoped public class RuleEngine extends Object
The Imixs RuleEngine is a CDI bean called by the WorkflowKernel to evaluate business rules part of an BPMN model.

The engine is based on the GraalVM script engine which provides an advanced polyglot language feature. This allows to evaluate scripts in different programming languages (e.g. Java, JavaScript, Ruby, Python, R, LLVM, WebAssembly, etc.).

From a BPMN Event element, the Script Language can be defined by the property 'txtBusinessRuleEngine' or by a a comment added to the first line of a script in the following format:

// graalvm.languageId=js

A Script can access all basic item values from the current workItem and also the event by the provided member variables 'workitem' and 'event'.

The CDI bean can be replaced by an alternative CDI implementation to provide an extended functionality.

NOTE: The implementation replaces the old RuleEngien which was based on the Nashorn Script Engine. The engine to detect deprecated scripts and convert them automatically into the new format. It is recommended to replace deprecated scripts.

Ralph Soika
  • Field Details

  • Constructor Details

    • RuleEngine

      public RuleEngine()
      This method initializes the default script engine.
    • RuleEngine

      public RuleEngine(String languageID)
      This method initializes the script engine with a specific languageId.
      scriptLanguage -
  • Method Details

    • getContext

      public org.graalvm.polyglot.Context getContext()
      Returns the current polyglot context This method implements a lazy initialization of the context. See Issue #822 We also set the option 'WarnInterpreterOnly' to false. See also here: Issue #821
    • putMember

      public void putMember(String identifier, Object value)
      Sets the value of a member using an identifier. The member value is subject to polyglot value mapping rules as described in Context.asValue(Object).
      identifier -
      value -
    • eval

      public org.graalvm.polyglot.Value eval(String script)
    • evaluateBooleanExpression

      public boolean evaluateBooleanExpression(String script, ItemCollection workitem) throws PluginException
      This method evaluates a boolean expression. An optional documentContext can be provided as member Variables to be used by the script
      documentContext - optional workitem context
    • evaluateBusinessRule

      public ItemCollection evaluateBusinessRule(String script, ItemCollection workitem, ItemCollection event) throws PluginException
      This method evaluates the business rule. The method returns the instance of the evaluated result object which can be used to continue evaluation. If a rule evaluation was not successful, the method returns null.

      An optional documentContext and a event object can be provided as member Variables to be used by the script

      workitem - optional document context
      event - optional bpmn event context
      evaluated result instance
    • convertResult

      public ItemCollection convertResult()
      This helper method converts the member variable 'result' of the current context into a Map object and returns a new instance of a ItemCollection holding the values of the map. var result={};'xxx';result.count=42;
      engine -
      ItemCollection holding the item values of the variable or null if no variable with the given name exists or the variable has not properties.