> By default, drools uses identity checks when
> asserting/modifying/retracting objects into/from working memory.
I just experienced otherwise :/ It does rely on equals/hashcode of the
facts:
When I overwrite Match with custom equals/hashcode methods, I get a
NullPointerException:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at
org.drools.reteoo.ReteooWorkingMemory.modifyObject(ReteooWorkingMemory.java:90)
at
org.drools.common.AbstractWorkingMemory.modifyObject(AbstractWorkingMemory.java:710)
at
net.sf.taseree.samples.travelingtournament.taseree.DayChangeMove.doMove(DayChangeMove.java:40)
on code like this:
FactHandle matchHandle = workingMemory.getFactHandle(match);
match.setDay(toDay);
workingMemory.modifyObject(matchHandle, match);
When I leave it out the equals/hashcode method on Match,
it works perfectly.
Problem is I need a different equals/hashcode method on my Match
objects, for the hashmaps I use myself.
Unlike Comparable and Comperator, there is no Equalitor class that I can
give as an argument to my hashmap.
With kind regards,
Geoffrey De Smet
Edson Tirelli wrote:
Geoffrey,
By default, drools uses identity checks when
asserting/modifying/retracting objects into/from working memory.
[]s
Edson
Geoffrey De Smet wrote:
Hi,
How does drools 3 use equals() (and hashCode()) ?
Here's my use case and why I am worrying about that:
A Match has a Long id, which identifies it (for database etc).
A number of Matches are asserted into the working memory.
A Match can be cloned, after which its properties
will differ from its clone,
but the id remains the same.
The clone is used for history
- a state in which the Match has been previously -
but isn't asserted into the working memory.
When the original Match is modified, the working memory is notified.
Outside of drools, I need to know when 2 matches with the same id are
in the same state, which I of course want to do with a simple HashMap.
So I want to override equals() (and hashCode()) so I can put them in
that HashMap, and basically do something like this:
if (id is the same || rest of state is also the same) {they are equal}
But I fear that that will mess up drools. I am right?
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