[jboss-jira] [JBoss JIRA] (DROOLS-664) Implement xpath notation in drools constraints
Mario Fusco created DROOLS-664:
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Summary: Implement xpath notation in drools constraints
Key: DROOLS-664
URL: https://issues.jboss.org/browse/DROOLS-664
Project: Drools
Issue Type: Feature Request
Reporter: Mario Fusco
Assignee: Mario Fusco
It is required to allow an xpath notation in drools constraints like the following:
{code}
Person( $pet : /pets )
{code}
that is formally equivalent to the more verbose:
{code}
Person( $pets : pets )
$pet : Pet() from $pets
{code}
It should be also possible to have conditions filtering the collection like in:
{code}
Person( $pet : /pets[ age == 5 ] )
{code}
corresponding to:
{code}
Person( $pets : pets )
$pet : Pet(age == 5) from $pets
{code}
Of course also multiple indirections has to be allowed, so the following:
{code}
Man( $toy : /wife/children/toys )
{code}
will be equivalent to:
{code}
$man: Man( $wife: wife )
$child: Child() from $wife.children
$toy: Toy() from $child.toys
{code}
In this case the xpath notation will also allow to flatten the 2 from nodes in a single
one that will internally flatten the collection of collections. Since it is necessary to
distinguish the case when we want to iterate a collection from the case when we want to
bind the collection as a whole it is possible to mix the collection iteration operator
'/' and the simple dereferencing operator '.' as in:
{code}
Man( $toys : /wife/children.toys )
{code}
In this last case this pattern binds each List<Toy> for each child as a whole, so
this is equivalent to:
{code}
$man: Man( $wife: wife )
Child( $toys: toys ) from $wife.children
{code}
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