Graphs in the Real World - Graph Databases - page 135

Here's the code for the ValidPathExpander :
private static class IntervalPathExpander implements PathExpander < Interval >
{
private final RelationshipType relationshipType ;
private final Direction direction ;
private IntervalPathExpander ( RelationshipType relationshipType ,
Direction direction )
{
this . relationshipType = relationshipType ;
this . direction = direction ;
}
@Override
public Iterable < Relationship > expand ( Path path ,
BranchState < Interval > deliveryInterval )
{
List < Relationship > results = new ArrayList < Relationship >();
for ( Relationship r : path . endNode ()
. getRelationships ( relationshipType , direction ) )
{
Interval relationshipInterval = new Interval (
( Long ) r . getProperty ( "start_date" ),
( Long ) r . getProperty ( "end_date" ) );
if ( relationshipInterval . contains ( deliveryInterval . getState () ) )
{
results . add ( r );
}
}
return results ;
}
}
The IntervalPathExpander 's constructor takes two arguments: a relationshipType
and a direction . This allows the expander to be reused for different types of relation‐
ships: in the case of the Global Post graph, the expander will be used to filter both
CONNECTED_TO and DELIVERY_ROUTE relationships.
The expander's expand() method takes the path to the current node, and the deliver
yInterval as supplied by the client. Each time it is called, expand() iterates the relevant
relationships on the current node (the current node is given by path.endNode() ). For
each relationship, the method then compares the relationship's interval with the delivery
interval. If the relationship's interval contains the delivery interval, the relationship is
added to the results.
Having looked at the IntervalPathExpander , we can now turn to the ParcelRouteCal
culator itself. This class encapsulates all the logic necessary to calculate a route between
the point where a parcel enters the network and the final delivery destination. It employs