Trying to retrieve Facts from Drools Working Memory

Asked Jan 19 '21 at 20:40

Active Jan 20 '21 at 18:26

Viewed 26 times

I am trying to search and retrieve a fact from the Drools Working Memory using a FactHandle but unable to do so. I am using the kieSession.getFactHandle(object) method in order to retrieve the fact, but it returns NullPointerException every time. Please correct me if I am implementing the FactHandle the wrong way. Below is my implementation:

Person person = new Person().setName("David").setAge(33);
FactHandle factHandle = kieSession.getFactHandle(person);
kieSession.update(factHandle, person); // NullPointerException

edited Jan 20 '21 at 18:26

asked Jan 19 '21 at 20:40

sam

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There are a lot of tests in the Drools codebase using the getFactHandle method, maybe you should start from that? This question is a bit too generic – Luca Molteni Jan 20 '21 at 09:26
@LucaMolteni Am I going in the wrong direction for searching a fact on the working memory? – sam Jan 20 '21 at 12:39
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So is this basically that you fired your rules and are now trying to get data out? – Roddy of the Frozen Peas Jan 20 '21 at 14:15
@RoddyoftheFrozenPeas I am trying to search the fact. consider a select query in case of SQL. – sam Jan 20 '21 at 18:23
That's even less clear than your question ... @sam – Roddy of the Frozen Peas Jan 20 '21 at 18:28
@RoddyoftheFrozenPeas I have inserted the Person object to kieSession. Now I want to retrieve it. – sam Jan 20 '21 at 18:30
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So you insert the Person into working memory, fire the rules, and now retrieve the Person? Do you not have the reference from when you inserted it? – Roddy of the Frozen Peas Jan 20 '21 at 18:34
@RoddyoftheFrozenPeas I donot have any reference to the person object but I do know the values of the field contained in the object. – sam Jan 20 '21 at 19:11

Trying to retrieve Facts from Drools Working Memory

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