[rules-users] Basic questions about rule deployment

[Godmar Back]

You'll have to provide your own classloader which can read resources
both from your .jar file and from where you keep your .drl files.

See java.net.URLClassLoader for how to do that. (Include two URLs: one
to your .jar, one where you keep the .drl files.) You can pass the
loader to the package builder.
Keep in mind that an absolute path in getResourceAsStream is relative
to each classpath entry in the classloader being used.

This is about all that's supported in Drools right now. I have opened
a JIRA enhancement request asking the JBoss developers to provide a
more flexible mechanism that allows both java code and drl files from
multiple sources to be loaded and combined, as was discussed on the
mailing list. I hope this issue may be addressed in the future as it
constitutes a real hindrance to using Drools in systems composed of
multiple rule providers.

 - Godmar

On 10/10/07, Fermion <henss at physik.uni-wuppertal.de> wrote:
>
> Hi,
>
> I've finished my first small application using JBoss Rules. My current
> deployment "strategy" is that I want to have a single executable .jar file
> containing my application and an external (not included in the .jar) folder
> that contains the rules that should be used.
>
> Unfortunately, this seems to be harder, than I thought, as my application
> refuses to use .drl or .dsl files that are outside of the package.
>
> I'm quite sure that it's just my misunderstanding of the manual that leads
> to the problem, as this seems to be one of the most basic deployment
> approaches, as stated by the manual:
>
> "
> Chapter 7. Deployment and Testing
> 7.1. Deployment options
>
> Once you have rules integrated in your application (or ideally before) you
> will need to plan how to deploy rules along with your application. Typically
> rules are used to allow changes to application business logic without
> re-deploying the whole application. This means that the rules must be
> provided to the application as data, not as part of the application (eg
> embedded in the classpath).
> "
>
> Unfortunately I have quite some problems understanding the rest of the
> chapter. So I just used and modified on of the given examples.
>
> CODE/*
>
> //read in the source
> Reader source = new
> InputStreamReader(JBossRules.class.getResourceAsStream(KNOWLEDGE_FILE));
>
> //read in the DSL
> Reader dsl = new
> InputStreamReader(JBossRules.class.getResourceAsStream(DOMAINSPECIFICLANGUAGE_FILE));
>
> //Use package builder to build up a rule package.
> //An alternative lower level class called "DrlParser" can also be used...
> PackageBuilder builder = new PackageBuilder();
>
> //Use the following instead of above if you are using a DSL:
> builder.addPackageFromDrl(source, dsl);
>
> */CODE
>
> If I use
>
> KNOWLEDGE_FILE = "/Rules_withDsl.drl";
> DOMAINSPECIFICLANGUAGE_FILE = "/Rules_withDsl.dsl";
>
> it all works wonderfully... but then the rules are within my .jar :-(
>
> So I tried to change this into a folder outside the package:
>
> KNOWLEDGE_FILE = "C:/test/Rules_withDsl.drl";
> DOMAINSPECIFICLANGUAGE_FILE = "C:/test/Rules_withDsl.dsl";
>
> Now, it doesn't work any more, because the "getResourceAsStream" returns
> null pointers...
>
> Any idea?
>
> Thanks
> --
> View this message in context: http://www.nabble.com/Basic-questions-about-rule-deployment-tf4601653.html#a13138467
> Sent from the drools - user mailing list archive at Nabble.com.
>
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