[rules-dev] Compiling drools-5 to .NET -- issue with ClassLoaders
Michael Neale
michael.neale at gmail.com
Thu Sep 3 22:33:42 EDT 2009
would have to look at the code for that - its the only documentation
that makes sense for something so low-level...
I don't think there were major changes in Drools 4 to 5 in that area -
so odd that it doesn't work.
On Fri, Sep 4, 2009 at 1:01 AM, kpowerinfinity<kpowerinfinity at gmail.com> wrote:
> Hi Mike,
>
> Do you remember what you needed to do for drools3.0? I had earlier
> compiled drools 4.0 and it seemed to work without any major problems.
>
> Where can I find some documentation on the ASM and where drools picks
> up the classes from while generating the "in-situ" classes?
>
> Thanks, Krishna.
>
> --
> http://kpowerinfinity.wordpress.com
> http://www.linkedin.com/in/kpowerinfinity
>
>
>
>
> On Thu, Sep 3, 2009 at 5:31 AM, Michael Neale<michael.neale at gmail.com> wrote:
>> Hi Krishna - I don't think the .Net version on the codehaus is kept
>> that up to date, so its probably a good thing you are doing what you
>> are doing with the latest.
>>
>> Yes, those accessor classes are indeed lazily generated and loaded
>> "in-situ" - this is for fast access of fields in the alpha network
>> which can be hit hard and often... an inlined version of the ASM
>> library is used to do this.
>>
>> I am pretty sure that even in drools 3 we did something like this
>> (also using ASM) and that was able to work with IKVM - so there must
>> be some small change that has made the IKVM classloader angry...
>>
>> On a barely related note: is it worth thinking about a Source to
>> Source translator to C# - there are a few around (ILog even open
>> sourced one, although it didn't cope with Generics last I checked...)
>> ?
>>
>>
>> Michael.
>>
>> On Wed, Sep 2, 2009 at 11:56 PM, kpowerinfinity<kpowerinfinity at gmail.com> wrote:
>>> Hello,
>>>
>>> I've been trying to compile the latest version of drools to .NET for a
>>> few days now. However, due to the classloaders structure, the classes
>>> in the org.drools.base.extractors.* are not found by the classloader,
>>> and the execution stops with a NoClassDefFoundError for classes in
>>> that package.
>>>
>>> Here's some details about the setup:
>>> Drools version: 5.0.1
>>> IKVM Version: 0.40.0.1
>>>
>>> I have successfully compiled all the required libraries into a DLL
>>> using IKVM, and a simple rule (containing a null LHS) runs
>>> successfully, all the classes are found, and the rule engine produces
>>> the correct output. However, when I add a condition into the LHS, it
>>> fails because it can't find one of the classes in
>>> /org.drools.base.extractors..*Reader/
>>>
>>> A sample rule I am using is:
>>> """
>>> package package
>>> import rules.Customer
>>> import rules.VoucherSeries
>>>
>>> rule "everything free for Krishna"
>>>
>>> when
>>> $c : Customer( firstname == "Krishna" )
>>> then
>>> VoucherSeries fact0 = new VoucherSeries();
>>> fact0.setSeriesCode( "FREE" );
>>> insert(fact0 );
>>> end
>>> """
>>>
>>> I have verified that all the classes are present in the classloader I
>>> am passing to the KnowledgeBuilderConfiguration. In fact, I also tried
>>> creating a MapBasedClassLoader that contains all the missing classes
>>> so that they can be easily found using fastFindClass. In the code
>>> listing below, both klass and klass2 resolve to the correct class
>>> objects.
>>>
>>> """
>>> java.util.Properties p = new java.util.Properties();
>>> p.put("drools.dialect.java.compiler", "JANINO");
>>> java.lang.ClassLoader cl =
>>> java.lang.Class.forName("org.drools.base.extractors.BaseLongClassFieldReader").getClassLoader();
>>> org.drools.rule.CompositeClassLoader compositeClassLoader
>>> = new org.drools.rule.CompositeClassLoader(cl);
>>>
>>> org.drools.rule.MapBackedClassLoader mbcl =
>>> getMapBackedClassLoader(cl);
>>>
>>> compositeClassLoader.addClassLoader(mbcl);
>>> java.lang.Class klass =
>>> compositeClassLoader.fastFindClass("rules.Customer");
>>> java.lang.Class klass2 =
>>> compositeClassLoader.fastFindClass("org.drools.base.extractors.BaseObjectClassFieldReader");
>>> java.lang.ClassLoader finalClassLoader = compositeClassLoader;
>>>
>>> org.drools.builder.KnowledgeBuilderConfiguration kbc =
>>> org.drools.builder.KnowledgeBuilderFactory.newKnowledgeBuilderConfiguration(p,
>>> finalClassLoader);
>>> """
>>>
>>> However, adding the DRL / PKG file, it fails with the exception:
>>>
>>> java.lang.NoClassDefFoundError was caught
>>> Message="org.drools.base.extractors.BaseObjectClassFieldReader"
>>> Source="IKVM.Runtime"
>>> StackTrace:
>>> at IKVM.NativeCode.java.lang.ClassLoader.defineClass1(Object
>>> thisClassLoader, String name, Byte[] b, Int32 off, Int32 len, Object
>>> pd, String source)
>>> at java.lang.ClassLoader.defineClass1(String , Byte[] , Int32 ,
>>> Int32 , ProtectionDomain , String )
>>> at java.lang.ClassLoader.defineClass(String name, Byte[] b,
>>> Int32 off, Int32 len, ProtectionDomain protectionDomain)
>>> at org.drools.base.ClassFieldAccessorCache.ByteArrayClassLoader.defineClass(String
>>> name, Byte[] bytes, ProtectionDomain domain)
>>> at org.drools.base.ClassFieldAccessorFactory.getClassFieldReader(Class
>>> clazz, String fieldName, CacheEntry cache)
>>> at org.drools.base.ClassFieldAccessorCache.CacheEntry.getReadAccessor(AccessorKey
>>> key, Class cls)
>>> at org.drools.base.ClassFieldAccessorCache.getReadAcessor(ClassFieldReader
>>> reader)
>>> at org.drools.base.ClassFieldAccessorStore.wire(ClassFieldReader reader)
>>> at org.drools.base.ClassFieldAccessorStore.getReader(String
>>> className, String fieldName, AcceptsReadAccessor target, AccessorType
>>> accessorType)
>>> at org.drools.base.ClassFieldAccessorStore.getReader(String
>>> className, String fieldName, AcceptsReadAccessor target)
>>> at org.drools.rule.builder.PatternBuilder.getFieldReadAccessor(RuleBuildContext
>>> context, BaseDescr descr, ObjectType objectType, String fieldName,
>>> AcceptsReadAccessor target, Boolean reportError)
>>> at org.drools.rule.builder.PatternBuilder.build(RuleBuildContext
>>> , Pattern , FieldConstraintDescr , AbstractCompositeConstraint )
>>> at org.drools.rule.builder.PatternBuilder.buildConstraint(RuleBuildContext
>>> , Pattern , Object , AbstractCompositeConstraint )
>>> at org.drools.rule.builder.PatternBuilder.build(RuleBuildContext
>>> context, BaseDescr descr, Pattern prefixPattern)
>>> at org.drools.rule.builder.PatternBuilder.build(RuleBuildContext
>>> context, BaseDescr descr)
>>> at org.drools.rule.builder.GroupElementBuilder.build(RuleBuildContext
>>> context, BaseDescr descr, Pattern prefixPattern)
>>> at org.drools.rule.builder.RuleBuilder.build(RuleBuildContext context)
>>> at org.drools.compiler.PackageBuilder.addRule(RuleDescr )
>>> at org.drools.compiler.PackageBuilder.addPackage(PackageDescr
>>> packageDescr)
>>> at org.drools.compiler.PackageBuilder.addPackageFromDrl(Resource
>>> resource)
>>> at org.drools.compiler.PackageBuilder.addKnowledgeResource(Resource
>>> resource, ResourceType type, ResourceConfiguration configuration)
>>> at org.drools.builder.impl.KnowledgeBuilderImpl.add(Resource
>>> resource, ResourceType type)
>>> at Capillary.Client.RulesEngine.RuleManager.ReadRules(String
>>> filename) in D:\coderoot\module\DataEntryClient-DVS\SubProjects\RulesEngine\RuleManager.cs:line
>>> 116
>>> InnerException:
>>>
>>> I saw the code at org/drools/base/ClassFieldAccessorCache.java, and it
>>> seems me that the Reader class for the particular type is being
>>> defined in situ using a byte[] array, but I am unable to understand
>>> why it can't load the class at that point.
>>>
>>> Can anybody with a better idea of the drools classloading structure
>>> guide me here?
>>>
>>> Also, is the drools.NET project active now? I would post all the steps
>>> I took for posterity.
>>>
>>> Thanks and Regards,
>>> Krishna.
>>>
>>> --
>>> http://kpowerinfinity.wordpress.com
>>> http://www.linkedin.com/in/kpowerinfinity
>>> _______________________________________________
>>> rules-dev mailing list
>>> rules-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-dev
>>>
>>
>>
>>
>> --
>> Michael D Neale
>> home: www.michaelneale.net
>> blog: michaelneale.blogspot.com
>>
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--
Michael D Neale
home: www.michaelneale.net
blog: michaelneale.blogspot.com
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