#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:
Platform you're using:
Mac OSX Lion

Reproduction steps:

include these entries in dependencies.yml file :

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

    - jboss:
        type: iBiblio
        root: "http://repository.jboss.org/nexus/content/groups/public-jboss/"
            - 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"
    $d: Discount()
    System.out.println("A discount <"+$d.label +"> is present");

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());

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...


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<h2>Play framework</h2>

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<h2>Reporting Security Vulnerabilities</h2> Since all bug reports are public, please report any security vulnerability directly to <em>guillaume dot bort at gmail dot com</em>.<br><br>

<h2>Creating a bug report</h2> Bug reports are incredibly helpful, so take time to report bugs and request features in our ticket tracker. We’re always grateful for patches to Play’s code. Indeed, bug reports with attached patches will get fixed far quickly than those without any.<br><br>

Please include as much relevant information as possible including the exact framework version you're using and a code snippet that reproduces the problem.<br><br>

Don't have too much expectations. Unless the bug is really a serious "everything is broken" thing, you're creating a ticket to start a discussion. Having a patch (or a branch on Github we can pull from) is better, but then again we'll only pull high quality branches that make sense to be in the core of Play.