And what will happen to any FactType objects out there? Or the Class<?> objects derived from them? Will it be safe to continue to use the object returned by KnowledgeAgent.getKnowledgeBase() which is documented to return a "cached KnowledgeBase"?
The current version of Drools does not support dynamic changes
in "type declarations" and I don't see this changing anytime soon.
The reason is that not only the actual fact would require changes,
but the actual knowledge base would require changes as several
nodes might be referencing the old class.
So, to update a fact type you need to recreate the
knowledge base. This is the same, BTW, than changing one of your
fact classes in your application jars... you need to recompile
the knowledge base or you will end up with class cast
exceptions, sooner or later.
Longer term there are two ways to achieve this
1) type declarations can only be modified if there is no data on
them and the existing rules are still valid after the change, i.e.
it will not effect the current state.
2) If ther eare existing facts a migration script must be provided
that handles the mapping as all beans would need to be copied to the
new type declaration.
Hi.
I have such declaration of type
declare Contact
firstName : String
end
then I want to add new property to this type. so the next
version is
declare Contact
firstName : String
newField : String
end
this type declaration is in separate drl file.
then I add this new type to current KnowledgeBase.
but when I execute knowledgeBase.getFactType("test.package",
"Contact");
I get old version of Contact.
During debugging I found the place where is should be
upgraded in the
KnowledgeBase.
org.drools.common.AbstractRuleBase.mergePackage
there is
// merge the type declarations
if ( newPkg.getTypeDeclarations() != null ) {
// add type declarations
for ( TypeDeclaration type :
newPkg.getTypeDeclarations().values() ) {
// @TODO should we allow overrides? only if
the class is not
in use.
if ( !pkg.getTypeDeclarations().containsKey(
type.getTypeName() ) ) {
// add to package list of type
declarations
pkg.addTypeDeclaration( type );
}
}
}
so according this comments it's not possible to upgrade Type
on the fly.
Am I missing something?
Does someone had such problems or know the workaround.