[rules-users] Re: Drools and Eclipse RCP

[J Michael Dean]

Sorry - I wrote this reply before realizing that you were asking about  
an "editor", not just incorporating Drools into an RCP.  I am posting  
this in case other are having the more mundane problem of making a RCP  
execute Drools rules.

- Mike

I have been trying to do this for a while, and have managed to create  
an RCP that does work.  I know at least one other person has responded  
on this list as having accomplished it.  His response indicated that  
he created a separate plugin for all the Drools components, and  
referred to it from his main plugin.  He also indicated that the  
objects needed for the DRL file had to be in the same plugin as the  
Drools engine components.

This has not been my experience.  I created a plugin that contains the  
Drools components and the dependent jars in the /lib folder of the  
Drools distribution.  That plugin's Manifest.mf file must be edited to  
add the line:

Eclipse-BuddyPolicy: registered

to the end because this will allow the plugin to access any other  
plugins that want to be accessed by the Drools plugin.  So suppose you  
name your plugin MinimalDrools;  the last line of the Manifest.mf  
shows that it is registered as a Eclipse buddy.

Now export the plugin in a deployable format, and then drag the new  
plugin into the Eclipse plugin folder and restart Eclipse.

Now your project plugin needs to depend on this newly added plugin.   
In addition, in your project plugin Manifest.mf, you must add the  
reciprocal part of the buddy registration:

Eclipse-RegisterBuddy: MinimalDrools

With this structure, I added a rules directory in the root of the  
plugin, and in my application code:

	private void fireDroolsRulesEngine() throws Exception {
		GlucoseDecisionState decisionState = new GlucoseDecisionState();
		Reader source;
		final PackageBuilder builder = new PackageBuilder();
		source = new InputStreamReader(FileLocator.toFileURL(
				GlucosePlugin.getDefault().getBundle().getEntry(
						"rules/GlucoseDroolRules00.drl")).openStream());
		builder.addPackageFromDrl(source);
		if (builder.hasErrors()) {
			System.out.println(builder.getErrors().toString());
		}

		Package pkg = builder.getPackage();
		RuleBase ruleBase = RuleBaseFactory.newRuleBase();
		ruleBase.addPackage(pkg);
		StatefulSession session = ruleBase.newStatefulSession();
		
		// setup the debug listeners
		session.addEventListener( new DebugAgendaEventListener() );
		session.addEventListener( new DebugWorkingMemoryEventListener() );
		
		// setup the audit logging
		final WorkingMemoryFileLogger glucoseLogger = new  
WorkingMemoryFileLogger( session );
		glucoseLogger.setFileName( "glucoseLogFile" );
		
		session.insert(decision,true);
		session.insert(decisionState,true);
		session.fireAllRules();
		glucoseLogger.writeToDisk();
		session.dispose();
	}

This works.  It is necessary to add the dependency of MinimalDrools to  
you feature, etc. if you are exporting a complete application.

This being said, I cannot successfully run JUnit tests on the Drools  
part of my RCP.  I can unit test everything else, including things  
like Hibernate, my database connections, etc.  But the MinimalDrools  
plugin does not satisfy some aspect of the Eclipse JUnit setup.  The  
Drools compiler does initialize, but something prevents the package  
from instantiating (several previous posts on this that remain  
unresolved).

Good luck.





>
> Date: Sat, 08 Dec 2007 19:04:52 +0100
> From: Michael Sizaki <Sizaki at gmx.de>
> Subject: [rules-users] Drools and eclipse RCP
> To: rules-users at lists.jboss.org
> Message-ID: <475ADCC4.2080305 at gmx.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi,
>
> is it possible to use the drools editor etc in an eclipse RCP
> application? At the moment, org.drools.eclipse plugin
> depends on debug and jdt and other eclipse IDE related
> plugins.....
>
> I would want a simple way for users to enter rules into
> my RCP application.
>
> Michael

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