12:43 a.m.
XStream is a simple library to serialize objects to XML and back again.
Sometimes it can get tedious to call all those XStream aliases/register
converter methods or you might simply like the new trend on configuring
POJOs: Java annotations.
While using annotations if you ever got this exception the there might be a
change that you forgot to call process annotation
XStream stream = new XStream(new DomDriver());
stream.processAnnotations(YourClassName.class);
Calling stream.processAnnotations(YourClassName.class); will clear down
this exception.
On Tue, May 29, 2012 at 11:40 PM, Francois Rouaix <francois.rouaix(a)gmail.com
wrote:
Folks,
I'm trying to use Drools in a mostly Java-less environment (rules are
written in .drl files, facts will be inserted from XML files). I'm running
into an issue where the XStream unmarshaller is unable to convert my XML to
a BatchExecutionCommand because it cannot find the class for a type
declared in the .drl file.
Is there any configuration required to make sure the XStream marshaller
knows about the dynamically generated classes from the .drl?
I'd appreciated any clues. I cannot add POJO classes for my types due to
the nature of the app.
Thanks.
DRL file
-----------
package com.example
declare Answers
....
end
/* some rules after this */
...
XML file
-----------
<batch-execution>
<insert>
<com.example.Answers>
....
Runner code
public static void Run(String xmlFactsFile, String drlFilename)
{
// Compile the drl file
KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add( ResourceFactory.newFileResource(drlFilename),
ResourceType.DRL );
if ( kbuilder.hasErrors() ) {
System.err.println( kbuilder.getErrors().toString() );
throw new RuntimeException("Cannot compile \"" + drlFilename +
"\"");
}
// kbase setup from the compiled rules
KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
kbase.addKnowledgePackages( kbuilder.getKnowledgePackages() );
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
File facts = new File(xmlFactsFile);
BatchExecutionCommand command = (BatchExecutionCommand)
BatchExecutionHelper.newXStreamMarshaller().fromXML(facts);
ExecutionResults bresults = ksession.execute(command);
System.out.println(BatchExecutionHelper.newXStreamMarshaller().toXML(bresults));
}
}
Error at runtime
----------------------
Exception in thread "main"
com.thoughtworks.xstream.converters.ConversionException:
com.example.Answers : com.example.Answers
---- Debugging information ----
message : com.example.Answers
cause-exception :
com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message : com.example.Answers
class : org.drools.command.runtime.rule.InsertObjectCommand
required-type : org.drools.command.runtime.rule.InsertObjectCommand
converter-type :
org.drools.runtime.help.impl.XStreamXML$InsertConverter
path : /batch-execution/insert/com.example.Answers
line number : 3
class[1] : org.drools.command.runtime.BatchExecutionCommandImpl
converter-type[1] :
com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version : null
-------------------------------
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
at
com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at
com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:318)
at
com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:230)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at
com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at
com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1035)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1019)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:930)
at
com.intentsoft.RulesEngine.RulesExecution.Run(RulesExecution.java:34)
at com.intentsoft.RulesEngine.Main.main(Main.java:10)
Caused by: com.thoughtworks.xstream.mapper.CannotResolveClassException:
com.example.Answers
at
com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:56)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:55)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:79)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:74)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
at
com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:45)
at
com.thoughtworks.xstream.core.util.HierarchicalStreams.readClassType(HierarchicalStreams.java:29)
at
com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:70)
at
org.drools.runtime.help.impl.XStreamXML$InsertConverter.unmarshal(XStreamXML.java:135)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
... 16 more
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