[rules-users] Run Drool Application From Command Prompt

[Greg Barton]

It's unclear from your post when you get the NPE: from the command line, from eclipse, or when integrated with OFBiz. (I assume you're referring to http://ofbiz.apache.org/)

It's undoubtedly a classpath issue.  Just peek at the source a bit.  I'm not sure what version you're using, but if you look at the source in the svn repo you'll see that line 92 of JavaDialectConfiguration is this:

getClass().getClassLoader().loadClass( "org.eclipse.jdt.internal.compiler.Compiler" );

See the javadoc for Class.getClassLoader() that says "Returns the class loader for the class. Some implementations may use null to represent the bootstrap class loader. This method will return null in such implementations if this class was loaded by the bootstrap class loader."

So, it looks probable that in the environment that's having problems, the JavaDialectConfiguration class is loaded by the bootstrap classloader.  What is the VM implementation you're using?

It might be best if Thread.currentThread().getContextClassLoader() was used instead of getClass().getClassLoader() in JavaDialectConfiguration and elsewhere.  Devs, have an opinion on that?

--- On Mon, 7/27/09, Pankaj.Jain at lntinfotech.com <Pankaj.Jain at lntinfotech.com> wrote:

> From: Pankaj.Jain at lntinfotech.com <Pankaj.Jain at lntinfotech.com>
> Subject: Re: [rules-users] Run Drool Application From Command Prompt
> To: rules-users at lists.jboss.org
> Date: Monday, July 27, 2009, 11:50 PM
> 
> 
> Hi
> 
> 
> 
> I still have not got any
> solution
> of my problem that I posted previously. I have included all
> required jar
> files and set proper class path .. Please do help ?
> 
> 
> 
> problem: 
> 
> 
> 
> 
> I am trying to
> integrate Drool with
> ofbiz and run application from command prompt. In one way I
> have integrated
> it properly and I am able to run it
> successfully.
> 
> 
> 
> 
> Code : Which I was using initially 
> 
> 
> 
> KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder();
> 
> 
> 
> 
> or 
> 
> 
> 
> PackageBuilderConfiguration cfg = new
> PackageBuilderConfiguration();
> 
> 
> KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder();
> 
> 
> 
> 
> Exception I got : 
> 
> 
> 
> org.drools.RuntimeDroolsException: Unable to load dialect
> 'org.drools.rule.builder.dialect.java.JavaDialectConfiguration:java
> 
> 
> :org.drools.rule.builder.dialect.java.JavaDialectConfiguration'
> 
> 
> at
> org.drools.compiler.PackageBuilderConfiguration.addDialect(PackageBuilderConfiguration.java:274)
> at
> org.drools.compiler.PackageBuilderConfiguration.buildDialectConfigurationMap(PackageBuilderConfiguration.java:259)
> 
> 
> 
> 
> at
> org.drools.compiler.PackageBuilderConfiguration.init(PackageBuilderConfiguration.java:176)
> at
> org.drools.compiler.PackageBuilderConfiguration.<init>(PackageBuilderConfiguration.java:153)
> at
> org.drools.compiler.PackageBuilder.<init>(PackageBuilder.java:242)
> 
> 
> . 
> 
> . 
> 
> . 
> 
> Caused by: java.lang.NullPointerException 
> 
> at
> org.drools.rule.builder.dialect.java.JavaDialectConfiguration.setCompiler(JavaDialectConfiguration.java:92)
> at
> org.drools.rule.builder.dialect.java.JavaDialectConfiguration.init(JavaDialectConfiguration.java:55)
> at
> org.drools.compiler.PackageBuilderConfiguration.addDialect(PackageBuilderConfiguration.java:270
> 
> 
> 
> 
> Problem I found : 
> 
> In the class JavaDialectConfiguration in jar file
> drools-compiler.jar there
> is a method named "setCompliler",  in this
> method Null Pointer
> Exception was coming. 
> 
> 
> 
> Solution I provided :
> 
> 
> In my application I created my custom class
> CustomJavaDialectConfiguration
> by extending to class JavaDialectConfiguration, In this
> class I overrided
> the method setCompiler. My method was exactly same as that
> of method setCompiler
> in JavaDialectConfiguration . To call my dialect class I
> also overrided
> the method "addDialect" of
> PackageBuilderConfiguration class
> . For that I created class
> CustomPackageBuilderConfiguration by extending
> to PackageBuilderConfiguration. 
> 
> after that I wrote the code: 
> 
> 
> 
> PackageBuilderConfiguration cfg = new
> CustomPackageBuilderConfiguration();
> 
> 
> KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder(cfg);
> 
> 
> 
> 
> 
> 
> Now application is running perfectly fine from both eclipse
> and command
> prompt without any exception. 
> 
> 
> 
> I want to know as my overrided method
> "setCompiler" was exactly
> same then why I had to override method, and In original
> code (ie in drools-compiler.jar
> file) why it was giving exception  ???  Was that
> due to class
> lader or something else ??  Please do help in this
> regard ....
> 
> 
> 
> 
>  
> 
> 
> 
> Thanks & Regards:
> 
> 
> 
> Pankaj Jain | L&T infotech |Navi Mumbai
> 
> Mobile: +91 9920218945
> 
> Email : pankaj.jain at lntinfotech.com
> 
> www.Lntinfotech.com
> 
> 
> 
> "Whatever the mind of man can conceive & believe,
> it can achieve."
> 
> 
> 
> Larsen & Toubro Infotech Ltd.
> 
> www.Lntinfotech.com
> 
> 
> 
> This Document is classified as: 
> 
> 
> 
> L&T
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> Infotech General Business   
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