com.amazon.carbonado.cursor

Class TransformedCursor<S,T>

java.lang.Object

com.amazon.carbonado.cursor.AbstractCursor<T>

com.amazon.carbonado.cursor.TransformedCursor<S,T>

Type Parameters:

S - source type, can be anything

T - target type, can be anything

All Implemented Interfaces:

Cursor<T>

public abstract class TransformedCursor<S,T>
extends AbstractCursor<T>

Abstract cursor which wraps another cursor and transforms each storable result into a target storable. This class can be used for implementing one-to-one joins. Use MultiTransformedCursor for one-to-many joins.

Author:

Brian S O'Neill

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TransformedCursor(Cursor<S> cursor)

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Call close to release any resources being held by this cursor.
boolean	hasNext() Returns true if this cursor has more elements.
T	next() Returns the next element from this cursor.
int	skipNext(int amount) Skips forward by the specified amount of elements, returning the actual amount skipped.
protected abstract T	transform(S storable) This method must be implemented to transform storables.

Methods inherited from class com.amazon.carbonado.cursor.AbstractCursor

copyInto, copyInto, toList, toList

Methods inherited from class java.lang.Object

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

Constructor Detail

TransformedCursor

protected TransformedCursor(Cursor<S> cursor)

Method Detail

transform

protected abstract T transform(S storable)
                        throws FetchException

This method must be implemented to transform storables. If the storable cannot be transformed, either throw a FetchException or return null. If null is returned, the storable is simply filtered out.

Returns:

transformed storable, or null to filter it out

Throws:

FetchException

close

public void close()
           throws FetchException

Description copied from interface: Cursor

Call close to release any resources being held by this cursor. Further operations on this cursor will behave as if there are no results.

Throws:

FetchException

hasNext

public boolean hasNext()
                throws FetchException

Description copied from interface: Cursor

Returns true if this cursor has more elements. In other words, returns true if next would return an element rather than throwing an exception.

Throws:

FetchException - if storage layer throws an exception

next

public T next()
       throws FetchException

Description copied from interface: Cursor

Returns the next element from this cursor. This method may be called repeatedly to iterate through the results.

Throws:

FetchException - if storage layer throws an exception

skipNext

public int skipNext(int amount)
             throws FetchException

Description copied from interface: Cursor

Skips forward by the specified amount of elements, returning the actual amount skipped. The actual amount is less than the requested amount only if the end of the results was reached.

Specified by:

skipNext in interface Cursor<T>

Overrides:

skipNext in class AbstractCursor<T>

Parameters:

amount - maximum amount of elements to skip

Returns:

actual amount skipped

Throws:

FetchException - if storage layer throws an exception