[rules-users] Serialization of packages: NotSerializableException (KnowledgePackageImp) and InvalidClassException (serialVersionUID)

[Bernd Rücker]

Has anybody an idea what’s these problems? I didn’t find any test cases,
are there any test cases for serializing the PKG files? What am I doing
wrong?







Von: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] Im Auftrag von Bernd Rücker
Gesendet: Dienstag, 1. September 2009 17:26
An: rules-users at lists.jboss.org
Betreff: [rules-users] WG: Serialization of packages:
InvalidClassException / serialVersionUID



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



/home/bruecker/workspace/1/iKS2/iks_drools_rules/drools-rules.pkg

Exception in thread "main" java.io.NotSerializableException:

org.drools.definitions.impl.KnowledgePackageImp

    at
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1156)

    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)

    at

org.drools.util.DroolsStreamUtils.streamOut(DroolsStreamUtils.java:79)

    at

org.drools.util.DroolsStreamUtils.streamOut(DroolsStreamUtils.java:61)





So this doesn’t work either
(http://downloads.jboss.com/drools/docs/5.0.1.26597.FINAL/drools-expert/ht
ml_single/index.html#d0e992):



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 );

out.close();



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> );

in.close();



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 [mailto:bernd.ruecker at camunda.com]
Gesendet: Dienstag, 1. September 2009 17:21
An: 'rules-users at lists.jboss.org'
Betreff: Serialization of packages: InvalidClassException /
serialVersionUID



Hi!



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: java.io.InvalidClassException:

  org.drools.impl.KnowledgeBaseImpl;

  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!



Cheers

Bernd



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