org.apache.tinkerpop.gremlin.process.traversal

Interface Traverser<T>

All Superinterfaces:

Cloneable, Comparable<Traverser<T>>, Serializable

All Known Subinterfaces:

Traverser.Admin<T>

public interface Traverser<T>
extends Serializable, Comparable<Traverser<T>>, Cloneable

A Traverser represents the current state of an object flowing through a Traversal. A traverser maintains a reference to the current object, a traverser-local "sack", a traversal-global sideEffect, a bulk count, and a path history.

Different types of traversers can exist depending on the semantics of the traversal and the desire for space/time optimizations of the developer.

Author:

Marko A. Rodriguez (http://markorodriguez.com)

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	Traverser.Admin<T> The methods in System.Traverser are useful to underlying Step and Traversal implementations.

Method Summary

Modifier and Type	Method and Description
default Traverser.Admin<T>	asAdmin() Typecast the traverser to a "system traverser" so Traverser.Admin methods can be accessed.
long	bulk() A traverser may represent a grouping of traversers to allow for more efficient data propagation.
Traverser<T>	clone() Traverser cloning is important when splitting a traverser at a bifurcation point in a traversal.
default int	compareTo(Traverser<T> other) If the underlying object of the traverser is comparable, compare it with the other traverser.
T	get() Get the object that the traverser is current at.
int	loops() Return the number of times the traverser has gone through a looping section of a traversal.
int	loops(String loopName) Return the number of times the traverser has gone through the named looping section of a traversal.
Path	path() Get the current path of the traverser.
default <A> A	path(Pop pop, String stepLabel)
default <A> A	path(String stepLabel) Get the object associated with the specified step-label in the traverser's path history.
<S> S	sack() Get the sack local sack object of this traverser.
<S> void	sack(S object) Set the traversers sack object to the provided value ("sack the value").
default <A> A	sideEffects(String sideEffectKey) Get a particular value from the side-effects of the traverser (thus, traversal).
default void	sideEffects(String sideEffectKey, Object sideEffectValue) Add a particular value to the respective side-effect of the traverser (thus, traversal).

Method Detail

get

T get()

Get the object that the traverser is current at.

Returns:

The current object of the traverser

sack

<S> S sack()

Get the sack local sack object of this traverser.

Type Parameters:

S - the type of the sack object

Returns:

the sack object

sack

<S> void sack(S object)

Set the traversers sack object to the provided value ("sack the value").

Type Parameters:

S - the type of the object

Parameters:

object - the new value of the traverser's sack

path

Path path()

Get the current path of the traverser.

Returns:

The path of the traverser

path

default <A> A path(String stepLabel)

Get the object associated with the specified step-label in the traverser's path history.

Type Parameters:

A - the type of the object

Parameters:

stepLabel - the step-label in the path to access

Returns:

the object associated with that path label (if more than one object occurs at that step, a list is returned)

path

default <A> A path(Pop pop,
                   String stepLabel)

loops

int loops()

Return the number of times the traverser has gone through a looping section of a traversal.

Returns:

The number of times the traverser has gone through a loop

loops

int loops(String loopName)

Return the number of times the traverser has gone through the named looping section of a traversal.

Parameters:

loopName - the name applied to the loop or null for the containing loop

Returns:

The number of times the traverser has gone through a loop

Throws:

IllegalArgumentException - if the loopName is not defined

bulk

long bulk()

A traverser may represent a grouping of traversers to allow for more efficient data propagation.

Returns:

the number of traversers represented in this traverser.

sideEffects

default <A> A sideEffects(String sideEffectKey)
                   throws IllegalArgumentException

Get a particular value from the side-effects of the traverser (thus, traversal).

Type Parameters:

A - the type of the returned object

Parameters:

sideEffectKey - the key of the value to get from the sideEffects

Returns:

the object in the sideEffects of the respective key

Throws:

IllegalArgumentException

sideEffects

default void sideEffects(String sideEffectKey,
                         Object sideEffectValue)
                  throws IllegalArgumentException

Add a particular value to the respective side-effect of the traverser (thus, traversal).

Parameters:

sideEffectKey - the key of the value to set int the sideEffects

sideEffectValue - the value to set for the sideEffect key

Throws:

IllegalArgumentException

compareTo

default int compareTo(Traverser<T> other)
               throws ClassCastException

If the underlying object of the traverser is comparable, compare it with the other traverser.

Specified by:

compareTo in interface Comparable<Traverser<T>>

Parameters:

other - the other traverser that presumably has a comparable internal object

Returns:

the comparison of the two objects of the traversers

Throws:

ClassCastException - if the object of the traverser is not comparable

asAdmin

default Traverser.Admin<T> asAdmin()

Typecast the traverser to a "system traverser" so Traverser.Admin methods can be accessed. This is used as a helper method to avoid the awkwardness of ((Traverser.Administrative)traverser). The default implementation simply returns "this" type casted to Traverser.Admin.

Returns:

The type-casted traverser

clone

Traverser<T> clone()

Traverser cloning is important when splitting a traverser at a bifurcation point in a traversal.