Question

I have a XML file containing metadata like a field’s maximum length. I have to use drools to build rules to validate this metadata against a list of facts. I don’t want to hardcode the name of each field that may or may not be specified in the XML.

I tried to do this :

when
   $metadata: Metadata(maxLength != null);
   $obj: Object(eval($metadata.getFieldName()).length > $metadata.maxLength);
then
   // TODO
end

It does not work and I get the following error :

java.lang.IllegalStateException: Errors while building rules : Unable
to Analyse Expression $metadata.getFieldName() > $metadata.maxLength:
[Error: Comparison operation requires compatible types. Found class
java.lang.String and class java.lang.Integer] [Near : {...
$metadata.getFieldName() > $metadata.maxLength ....}]

Is it possible to dynamically get a field name and compare its maximum length? Will I have to create a java object to accomplish this?

Thank you

Answer 1

Finally, I have decided to generate my drools file dynamically from my XML using rule templates.