Hi folks,
Can anyone explain how stateless session execution results should work? Working
through the docs and tracing the code, it’s getting a bit confusing.
Firstly, according to the user manual, one should be able to insert a list of
facts as a Command, and get an instance of ExecutionResults back, which can
then be queried. Here’s the example code:
StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();
Command cmd = CommandFactory.newInsertElements( Arrays.asList( Object[] {
new Cheese( "stilton" ),
new Cheese( "brie" ),
new Cheese( "cheddar" ),
});
ExecutionResults bresults = ksession.execute( cmd );
That doesn’t compile, so I fixed it as follows:
Command cmd = CommandFactory.newInsertElements( Arrays.asList(
new Cheese( "stilton" ),
new Cheese( "brie" ),
new Cheese( "cheddar" )
));
ExecutionResults bresults = ksession.execute( cmd );
This does now compile, but running it throws a ClassCastException:
java.lang.ClassCastException: java.util.ArrayList cannot be cast to
org.drools.runtime.ExecutionResults
Taking a look through the Drools code, it would appear that Command has a
generic type, which in the case of an InsertElementsCommand is:
GenericCommand<Collection<FactHandle>>
In turn, the execute command in StatelessKnowledgeSessionImpl casts its result
to that generic type:
public <T> T execute(Command<T> command) {
Object o = ((GenericCommand) command).execute( context );
...
return (T) o;
So the ClassCastException is because the execute method returns an ArrayList of
FactHandle instead of an ExecutionResults.
I’m assuming that I must have got the wrong end of the stick somewhere, so what
should I be doing to get an ExecutionResults from a stateless session, which I
can then query?
Cheers,
Steve_______________________________________________
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