cz.cuni.pogamut.posh.explorer
Class Crawler<T>

java.lang.Object
  cz.cuni.pogamut.posh.explorer.Crawler<T>

Type Parameters:

T - what is crawler crawling

public abstract class Crawler<T>
extends Object

One time use class for crawling the primitives and providing them to the explorer.

Author:

Honza

Field Summary

protected Set<T>	cache Set of all values found by this crawler.
protected Set<T>	cacheUm Unmodifiable wrapper of cache.
protected Set<CrawlerListener<T>>	listeners Set of listeners for crawler.
protected Set<CrawlerListener<T>>	listenersUm Unmodifiable wrapper of listeners.

Constructor Summary

Crawler()

Method Summary

boolean	addListener(CrawlerListener<T> listener) Add listener for crawler.
abstract void	crawl() Start crawling for the primitives.
abstract void	die() Terminate the crawler, once this is called, crawler should die and liseners shouldn't recieve any further messages.
abstract String	getDescription() Get description of the primitive.
abstract String	getName() Get name of primitive this provider is crawling
protected void	notifyCrawledData(Collection<T> data) Notify all listeners that we have new data as result of diligent crawling.
protected void	notifyFinished(boolean error) Notify all listeners that crawling has been finished.
protected void	notifyStarted() Notify all listeners that crawling has started.
boolean	removeListener(CrawlerListener<T> listener) Remove crawler listener from set of listeners.

Methods inherited from class java.lang.Object

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

Field Detail

listeners

protected final Set<CrawlerListener<T>> listeners

Set of listeners for crawler. Please use unmodifiable version.

listenersUm

protected final Set<CrawlerListener<T>> listenersUm

Unmodifiable wrapper of listeners.

cache

protected final Set<T> cache

Set of all values found by this crawler.

cacheUm

protected final Set<T> cacheUm

Unmodifiable wrapper of cache.

Constructor Detail

Crawler

public Crawler()

Method Detail

getName

public abstract String getName()

Get name of primitive this provider is crawling

Returns:

name of primitive (lower case, human readable)

getDescription

public abstract String getDescription()

Get description of the primitive. What does it do ect.

Returns:

description of primitive

crawl

public abstract void crawl()

Start crawling for the primitives. All you need to do is to call this method, it will notify listeners about progress and in due time it terminates itself (no need for programmer to take care about that).
DO NOT CALL TWICE, create new crawler in you need to.
Once crawling starts, it will notify listeners about progress(using CrawlerListener).
If you have to stop the crawling prematurely, use {@link Crawler#die() }.

See Also:

CrawlerListener

die

public abstract void die()

Terminate the crawler, once this is called, crawler should die and liseners shouldn't recieve any further messages. This will notify all listeners with CrawlerListener#finished(boolean) .

addListener

public final boolean addListener(CrawlerListener<T> listener)

Add listener for crawler.

Parameters:

listener - listener to add

Returns:

true if listener wans't already in the set of all listeners

removeListener

public final boolean removeListener(CrawlerListener<T> listener)

Remove crawler listener from set of listeners.

Parameters:

listener - listener to remove

Returns:

true if listener was in set of crawler listeners.

notifyStarted

protected final void notifyStarted()

Notify all listeners that crawling has started.

notifyCrawledData

protected final void notifyCrawledData(Collection<T> data)

Notify all listeners that we have new data as result of diligent crawling.

notifyFinished

protected final void notifyFinished(boolean error)

Notify all listeners that crawling has been finished.

Parameters:

error - am I ending due to an error?