Package 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
    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
    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.
    default int
    loops()
    Return the number of times the traverser has gone through a looping section of a traversal.
    default 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(String stepLabel)
    Get the object associated with the specified step-label in the traverser's path history.
    default <A> A
    path(Pop pop, String stepLabel)
     
    <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 Details

    • 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

      default 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

      default 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<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.