conditionExpression - how to access static methods

zhn — Mon, 20 Apr 2015 09:02:14 GMT

Hi there!I'd like to use a static method call inside a conditional expression of my sequence flow. Is there any way to import classes to the juel expression context? As far as I see, this context just knows about process variables and spring beans. Therefore I get an ActivitiException telling me: "U

Re: conditionExpression - how to access static methods

zhn — Mon, 20 Apr 2015 12:48:01 GMT

Hi again,

I worked on this problems for a couple of hours now and somehow solved it for my use case. Actually I couldn't find a point to access the ELContext of juel. However I found a workaround by implementing a service bean that wraps the expression evaluation. We do not use juel anymore but forward to a javax EL 3.0 glassfish implementation.

Maybe someone also wants to use this solution as well. So here's what our conditionExpression now looks like:


<sequenceFlow id="checkSalary" sourceRef="1234" targetRef="4321">
    <conditionExpression xsi:type="tFormalExpression">${javaxEL.eval("#{Money.less(salary, Money.valueOf(\"1500 EUR\")}", execution)}</conditionExpression>
</sequenceFlow>

My service bean (id="javaxEL") just forwards the evaluation to javax EL 3.0 glassfish implementation. The execution property point to the current variable scope:


public class ActivitiJavaxELConnector {
  public Object eval(String expr, VariableScope scope) {
      ExpressionFactory factory = ExpressionFactory.newInstance();
      ELContext context = new StandardELContext(factory);
      
      // import packages
      context.getImportHandler().importPackage("de.myexample.valuetypes");  

      // add variables to context
      for (Entry<String, Object> v : scope.getVariables().entrySet()) {
        context.getELResolver().setValue(context, null, v.getKey(), v.getValue());
      }
      
      // evaluate
      return factory.createValueExpression(context, expr, Object.class).getValue(context);
  }
}

Haven't tested this for all use cases. Probably beans now cannot be used within the forwarded expression. However we don't use that in a conditionExpressions normally. Maybe this is not the smartest solution but it just works for us… 😉

Would be great if activiti could support the JSR-223 script engines to be used for conditionExpression as well… just like for script tasks. However I couldn't find something about that.

Best, Christin

Re: conditionExpression - how to access static methods

jbarrez — Tue, 21 Apr 2015 08:27:21 GMT

> Would be great if activiti could support the JSR-223 script engines to be used for conditionExpression as well… just like for script tasks.
> However I couldn't find something about that.

No it does not support that. I do like the idea …

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conditionExpression - how to access static methods

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