The exception of the KnowledgePackage serialization (by the way, this is described in the docs, that you can serialize the KnowledgePackages!):



Exception in thread "main"










So this doesn’t work either (


3.2.4. Building and Deployment in Separate Processes

Both the KnowledgeBase and the KnowledgePackage are units of deployment and serializable. This means you can have one machine do any necessary building, requiring drools-compiler.jar, and have another machine deploy and execute everything, needing only drools-core.jar.

Although serialization is standard Java, we present an example of how one machine might write out the deployment unit and how another machine might read in and use that deployment unit.

Example 3.15. Writing the KnowledgePackage to an OutputStream

ObjectOutputStream out = new ObjectOutputStream( new FileOutputStream( fileName ) );

out.writeObject( kpkgs );



Example 3.16. Reading the KnowledgePackage from an InputStream

ObjectInputStream in = new ObjectInputStream( new FileInputStream( fileName ) );

// The input stream might contain an individual

// package or a collection.

@SuppressWarnings( "unchecked" )

Collection<KnowledgePackage> kpkgs =

    ()in.readObject( Collection<KnowledgePackage> );



KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();

kbase.addKnowledgePackages( kpkgs );


The KnowledgeBase is also serializable and some people may prefer to build and then store the KnowledgeBase itself, instead of the Knowledge Packages.

Drools Guvnor, our server side management system, uses this deployment approach. After Guvnor has compiled and published serialized Knowledge Packages on a URL, Drools can use the URL resource type to load them.



Von: Bernd Rücker []
Gesendet: Dienstag, 1. September 2009 17:21
An: ''
Betreff: Serialization of packages: InvalidClassException / serialVersionUID




I really struggled some time with serialization issues: I want to create a pkg and package that with the jar. >From there I want to read it during runtime.


Easy I thought. Drools 5 way should be to serialize the KnowledgeBase, right? At least, this is what the AntTask does.


If I try to serialize the KnowledgePackage I get an excpetion anyway:



Okay. Back to the KnowledgeBase. Serialized with Drools 5.0.0.M4 and try to read it with 5.0.0.M5:


Caused by:


  local class incompatible: stream classdesc serialVersionUID = -4540376767025107954,

  local class serialVersionUID = -3186110098262381425


So it seems Drools Packages are NOT compatible between minor versions? This would be a disaster for deployment. Or do I serialize the wrong thing? Unfortunately I didn’t find anything in the docs about it.


Then I tried to do it the “old” Drools 4 way and serialize Package objects, but same problem with a different serialVersionUID!


Why do these important classes don’t have a serialVersionUID? Or how should that be loaded? Must be a big issue with Govner, so I think there must be a solution already?


Thanks for any help!