com.tinkerpop.pipes

Class AbstractPipe<S,E>

java.lang.Object

com.tinkerpop.pipes.AbstractPipe<S,E>

All Implemented Interfaces:

Pipe<S,E>, Iterable<E>, Iterator<E>

Direct Known Subclasses:

AbstractMetaPipe, AggregatePipe, CollectionFilterPipe, CountPipe, CyclicPathFilterPipe, DuplicateFilterPipe, EdgesVerticesPipe, ExpandablePipe, FilterFunctionPipe, FunctionPipe, GatherFunctionPipe, GatherPipe, GroupByPipe, GroupCountFunctionPipe, GroupCountPipe, HasCountPipe, IdEdgePipe, IdentityPipe, IdFilterPipe, IdPipe, IdVertexPipe, IfThenElsePipe, IntervalFilterPipe, LabelFilterPipe, LabelPipe, LinkPipe, ObjectFilterPipe, OrderMapPipe, OrderPipe, PathPipe, PropertyFilterPipe, PropertyMapPipe, PropertyPipe, QueryPipe, RandomFilterPipe, RangeFilterPipe, ScatterPipe, SelectPipe, ShufflePipe, SideEffectFunctionPipe, StorePipe, TablePipe, ToStringPipe, TransformFunctionPipe, TreePipe, VerticesEdgesPipe, VerticesVerticesPipe

public abstract class AbstractPipe<S,E>
extends Object
implements Pipe<S,E>

An AbstractPipe provides most of the functionality that is repeated in every instance of a Pipe. Any subclass of AbstractPipe should simply implement processNextStart(). The standard model is

 protected E processNextStart() throws NoSuchElementException {
   S s = this.starts.next();
   E e = // do something with the S to yield an E
   return e;
 }
 

If the current incoming S is not to be emitted and there are no other S objects to process and emit, then throw a NoSuchElementException.

Author:

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

Field Summary

Fields

Modifier and Type	Field and Description
protected E	currentEnd
protected boolean	pathEnabled
protected Iterator<S>	starts

Fields inherited from interface com.tinkerpop.pipes.Pipe

NO_PATH_MESSAGE

Constructor Summary

Constructors

Constructor and Description
AbstractPipe()

Method Summary

Methods

Modifier and Type	Method and Description
void	enablePath(boolean enable) Calculating paths can be an expensive operation for some pipes.
List	getCurrentPath() Returns the transformation path to arrive at the current object of the pipe.
protected List	getPathToHere()
boolean	hasNext()
Iterator<E>	iterator() The iterator method of Iterable is not faithful to the Java semantics of iterator().
E	next()
protected abstract E	processNextStart()
void	remove()
void	reset() A pipe may maintain state.
void	setStarts(Iterable<S> starts) Set an iterable of S objects to the head (start) of the pipe.
void	setStarts(Iterator<S> starts) Set an iterator of S objects to the head (start) of the pipe.
void	setStarts(Pipe<?,S> starts)
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

starts

protected Iterator<S> starts

currentEnd

protected E currentEnd

pathEnabled

protected boolean pathEnabled

Constructor Detail

AbstractPipe

public AbstractPipe()

Method Detail

setStarts

public void setStarts(Iterator<S> starts)

Description copied from interface: Pipe

Set an iterator of S objects to the head (start) of the pipe.

Specified by:

setStarts in interface Pipe<S,E>

Parameters:

starts - the iterator of incoming objects

setStarts

public void setStarts(Iterable<S> starts)

Description copied from interface: Pipe

Set an iterable of S objects to the head (start) of the pipe.

Specified by:

setStarts in interface Pipe<S,E>

Parameters:

starts - the iterable of incoming objects

setStarts

public void setStarts(Pipe<?,S> starts)

reset

public void reset()

Description copied from interface: Pipe

A pipe may maintain state. Reset is used to remove state. The general use case for reset() is to reuse a pipe in another computation without having to create a new Pipe object. An implementation of this method should be recursive whereby the starts (if a Pipe) should have this method called on it.

Specified by:

reset in interface Pipe<S,E>

getCurrentPath

public List getCurrentPath()

Description copied from interface: Pipe

Returns the transformation path to arrive at the current object of the pipe.

Specified by:

getCurrentPath in interface Pipe<S,E>

Returns:

a List of all of the objects traversed for the current iterator position of the pipe.

remove

public void remove()

Specified by:

remove in interface Iterator<E>

next

public E next()

Specified by:

next in interface Iterator<E>

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<E>

enablePath

public void enablePath(boolean enable)

Description copied from interface: Pipe

Calculating paths can be an expensive operation for some pipes. This method is used to activate or deactivate the calculation of paths. The default state of a newly constructed pipe should have its path calculations disabled. An implementation of this method should be recursive whereby the starts (if a Pipe) should have this method called on it.

Specified by:

enablePath in interface Pipe<S,E>

Parameters:

enable - enable path calculations

iterator

public Iterator<E> iterator()

The iterator method of Iterable is not faithful to the Java semantics of iterator(). This method simply returns the pipe itself (which is an iterator) and thus, is useful only for foreach iteration.

Specified by:

iterator in interface Iterable<E>

Returns:

the pipe from the perspective of an iterator

toString

public String toString()

Overrides:

toString in class Object

processNextStart

protected abstract E processNextStart()
                               throws NoSuchElementException

Throws:

NoSuchElementException

getPathToHere

protected List getPathToHere()