我如何读取在KieSession外部插入的事实（例如规则结果）？

Question

During my rules execution, I will be "inserting" new fact object in memory that I will need to read when the rules are done firing. How can I read those facts when outside the Rules Session?

I have tried to insert the fact with an outIdentifier, from outside the session (ie before the "fireAllRules()" method). However, because I may not know how many AccountingPeriod fact may get inserted during the rule session, or even if it will get inserted, this method does not seem suitable.

Accounting Period Fact:

package sample.package;

public class AccountingPeriod {

    private LocalDate accountingDate;
    private int personKey;

    public AccountingPeriod(LocalDate accountingDate, int personKey) {
        this.accountingDate = accountingDate;
        this.personKey = personKey;
    }

    public LocalDate getAccountingDate() { return accountingDate; }
    public LocalDate getPersonKey() { return personKey; }
}

Execution Code :

sample.package;
public static void main(String args[]) {
    StatelessKieSession ksession = [initialized KieSession]

    ksession.execute(Arrays.asList(Facts[]));
    [Code here to get the AccountingPeriod fact inserted in the rule session]
}

myRules.drl

rule
    when [some condition]
    then
        insert (new AccountingPeriod(LocalDate.of(year, month, day), 100));
end

Answer 1

I see several options.

1) Insert one more object to session from the very beginning and use it as result container.

Person person = new Person();
person.setAge(15);
List result = new ArrayList();
kieSession.execute(Arrays.asList(person,result));
assertThat(result.get(0)).isEqualTo("haha");


rule "Check person age"
    when
        $person : Person( age > 16 );
        $result : List ( );
    then
        insert(new IsCoder( $person ) );
        $result.add("haha");
    end

2) Instead of using StatelessKieSession you can use just KieSession . KieSession has getObjects method where you can find all objects inserted and iterate through them.

Answer 2

I just found a way to get the facts from a stateless KieSession.

sample.package;
public static void main(String args[]) {
    StatelessKieSession ksession = [initialized KieSession]
    List<Command> cmds = new ArrayList<>();

    cmds.add([all required commands]);
    cmds.add(CommandFactory.newFireAllRules());
    cmds.add(CommandFactory.newGetObjects("facts"));
    ExecutionResults rulesResults = kSession.execute(CommandFactory.newBatchExecution(cmds));
    Collection<Object> results = (Collection<Object>) rulesResults.getValue("facts");
}

It turns out that by linking a command to an OutIdentifier ( "facts" , in this case) we can get its return value by using the getValue(outIdentifier) of the KieSession results.

Answer 3

In my case simply ksession.execute(myPojoObject) worked.

But make sure the package structure of myPojoObject in application corresponds to that of deployed kJar (via kie-workbench).