[rules-users] Drools' use of hashCode

[Wolfgang Laun]

This is the state of things in connection with hashCode, update and object
comparison:


   - There is a fact type A with a field b of class B and
   - patterns for A use constraints comparing b with "==" to some other
   object of type B and
   - B overrides hashCode using a field c of B and
   - this field is changed in an update of some object B.

In any situation like this, it is necessary to instruct the engine that any
fact of type A containing a reference to the changed fact B has changed.

In most real-world situation, this may not be possible. Then,

   - either avoid constraining on object references by replacing this with
   primary key field constraints,
   - or refrain from using c in hashCode.

-W


On 22 June 2011 13:58, M. H. <hugues_81 at hotmail.com> wrote:

> And yet the funny thing is it does affect the other fact:
> if you run this without the hashCode and equals method, it works fine, but
> if you run it with hashCode and equals overriden, the second rule won't be
> executed.
> You mentionned before the usual rules for hashCode and equals, what are
> they
> appart from equals=>equal hashCodes? I don't understand why this works in a
> case and not in the other, so maybe I'm missing something here?
>
> Thanks,
>
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