#1430 confirmed
Rémy Coqueugniot

Play and Drools class path problems during DRL compilation

Reported by Rémy Coqueugniot | February 15th, 2012 @ 04:56 PM | in 1.4.x

Framework version:
1.2.4
Platform you're using:
Mac OSX Lion

Reproduction steps:

include these entries in dependencies.yml file :

require:
    - play
    - org.drools -> drools-core 5.3.1.Final
    - org.drools -> drools-compiler 5.3.1.Final

repositories:
    - jboss:
        type: iBiblio
        root: "http://repository.jboss.org/nexus/content/groups/public-jboss/"
        contains:
            - org.drools -> *
            - janino -> *

Add a new POJO class:

package models;

public class Discount {
    public String label;
}

Add a basic Rules.drl file in your project :

package rules;
import models.Discount;
rule "R1"
  when
    $d: Discount()
  then
    System.out.println("A discount <"+$d.label +"> is present");
end

Try to compile it from a Controller :

public class Application extends Controller {
 public static void index() {
  KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
  kbuilder.add(ResourceFactory.newFileResource("Rules.drl"), ResourceType.DRL);
  if (kbuilder.hasErrors()) {
   throw new CompilationException(kbuilder.getErrors().toString());
  }
  ok();
 }
}

You'll get an error from the Drools compiler :

Rule Compilation error : [Rule name='R1']
 rules/Rule_R1.java (2:22) : Only a type can be imported. models.Discount resolves to a package
 rules/Rule_R1.java (6:211) : models.Discount cannot be resolved to a type

Meaning the Play.classLoader could not load the declared class to import ?

We can pass a classLoader to the Drools compiler :

 final KnowledgeBuilderConfiguration kBaseConf = KnowledgeBuilderFactory.newKnowledgeBuilderConfiguration(Play.configuration, Play.classloader);
 KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(kBaseConf);
//(...)

But with the same issue.

A workaround have been seen to modify the framework/pym/play/application.py with those lines :

 # The default
 classpath.append(os.path.normpath(os.path.join(self.path, 'conf')))
 classpath.append(os.path.normpath(os.path.join(os.path.join(self.path, 'tmp'), 'classes')))
 classpath.append(os.path.normpath(os.path.join(self.play_env["basedir"], 'framework/play-%s.jar' % self.play_env['version'])))

at the beginning of the def getClasspath(self) method.

I'm not sure about the effect of such modification...

-R-

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<h2>Play framework</h2>

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