Hmm … so the use of batch execution instead of InsertObjectCommand improved things. However I have noticed that although rules are activating as expected, and facts are being inserted, my queries don’t seem to get any results. For instance with the following code:
Based on a stateless session:
List<Command> cmds = new ArrayList<Command>();
cmds.add(CommandFactory.newInsert(new IbanValidationRequest(iban), "request"));
cmds.add(CommandFactory.newQuery("annotations", "annotations"));
ExecutionResults results = ksession.execute(CommandFactory.newBatchExecution(cmds));
QueryResults queryResults = ( QueryResults ) results.getValue( "annotations" );
System.out.println("Found [" + queryResults.size() + "]");
Based on a stateful session:
statefulSession.insert(new IbanValidationRequest(iban));
statefulSession.fireAllRules();
QueryResults queryResults = statefulSession.getQueryResults("annotations");
System.out.println("Found [" + queryResults.size() + "]");
What I’m finding is that if I invoke a query against a stateful session, I get a result. However, with stateless sessions, I am examining the ExecutionResults, and finding that they do contain a reference to an “annotations” QueryResults. However that collection of query results is empty.
btw - I’m also noticing that the code example in the user guide for batch executions with queries doesn’t use the current syntax for adding a query command. I’m guessing this syntax changed without an associated update to the user guide.
Steve
The mean thing is that the code
org.drools.command.CommandFactory
uses the generic interface
org.drools.command.Command<T>
for all commands without specifying the generic parameter with the many
newXyz methods. If it were written well, it would tell you what to
expect from the command execution, since interface
org.drools.runtime.CommandExecutor
has the generic
<T> T execute(Command<T> command)
So you dig around in the code and may detect that ksession.execute(
cmd ) with cmd being made by newInsertElements(...) returns a
Collection<FactHandle>. Mighty helpful.
Fixing the Experts would help a little, avoiding utter stupefaction.
Cheers
-W
On 11/12/2013, Stephen Masters <stephen.masters@me.com> wrote:
Thanks for that, Wolfgang. I have been working on something else for a few
days, but just switched over to batch execution, and that is giving me some
appropriate results (my tests are passing).
Which leads me to the question ...
Given that Example 3.4.1 in the Drools 5.5.0.Final user guide does not
compile, is that because there is a bug in the implementation of command
execution? Or is it a bug in the example. i.e.
The results should just not be assigned to anything?
The results (an ArrayList containing the facts which were just inserted)
should be assigned to a List of Object?
The example should just be removed from the user guide, as it is no longer a
valid/recommended approach?
Anybody with thoughts on that? Assuming that the answer is a documentation
fix, I’ll be happy to correct it appropriately and submit a pull request.
Cheers,
Steve
On 4 Dec 2013, at 12:24, Wolfgang Laun <wolfgang.laun@gmail.com> wrote:
I think you have to put your insert command into a list
List<Command<?>> cmds = new ArrayList();
and pass this via batch execution
CommandFactory.newBatchExecution( cmds )
-W
On 04/12/2013, Stephen Masters <stephen.masters@me.com> wrote:
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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