ISSearch
Class ISCrawler

java.lang.Object
  ISSearch.ISCrawler

All Implemented Interfaces:

ISCrawlerInterface, java.lang.Runnable

public class ISCrawler
extends java.lang.Object
implements ISCrawlerInterface

The Crawler class of the Web search engine. This class is used to start and stop the Crawler, to reset the engine and to control crawling parameters.

See Also:

Runnable, Thread, InetAddress, URL, HttpURLConnection, InputStreamReader, BufferedReader, Exception

Field Summary

Fields inherited from interface ISSearch.ISCrawlerInterface

RUNNING, STOPPED

Constructor Summary

ISCrawler()
Creates a new instance of ISCrawler

Method Summary

void	addLink(java.net.URL link) Adds a new link to the URL queue, if the link is not yet visited.
java.net.URL	getBest() Returns the best candidate to be visited next.
java.lang.String	getContentType(java.net.URLConnection urlConnection) Returns the ContentType of the current document.
int	getCrawlingDepth() Returns the current maximum allowed crawling depth.
ISDocumentInterface	getCurrentDocument() Returns the last document visited by the Crawler.
java.net.URL	getCurrentURL() Returns the last URL visited by the Crawler.
int	getMaxQueueSize() Returns the maximum allowed size of the URL Queue
java.net.URL	getNextURL() Returns the next URL to be searched.
int	getQueueSize() Returns the current size of the URL queue
int	getState() Returns the current state of the crawler.
int	getTimeout() Returns the current timeout of the crawler.
boolean	isDataStructureEmpty() Checks if our data structure is empty or not.
boolean	isVisited(java.net.URL doc) Checks if the URL of the given document is already visited by the crawler.
static void	main(java.lang.String[] args)
void	reset() Resets the crawler.
boolean	robotSafe(java.net.URL url) Checks if there exists a robots.txt on the server and checks it contains a "Disallow:".
void	run()
ISDocumentInterface	runParser(java.io.Reader r) Starts the parser.
void	setCrawlingDepth(int depth) Sets the maximum allowed crawling depth.
void	setCurrentDocument(ISDocumentInterface isd) Sets the last document visited by the Crawler.
void	setQueueMaxSize(int m) Set the maximum allowed size of the URL queue
void	setState(int state_code) Sets the current state of the crawler.
void	setTimeout(int t) Sets the current timeout of the crawler.
void	start() Starts the thread of the crawler and changes the engine state to RUNNING
void	stop() Stops the crawler.

Methods inherited from class java.lang.Object

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

Constructor Detail

ISCrawler

public ISCrawler()

Creates a new instance of ISCrawler

Method Detail

addLink

public void addLink(java.net.URL link)

Adds a new link to the URL queue, if the link is not yet visited.

Specified by:

addLink in interface ISCrawlerInterface

Parameters:

link - The URL link representation of the new target

getBest

public java.net.URL getBest()

Returns the best candidate to be visited next. The result must have the highest priority (in the sense of the selected ordering strategy) under all available links.

Specified by:

getBest in interface ISCrawlerInterface

Returns:

The best target to be visited by the Crawler next, null if the queue is empty.

getCrawlingDepth

public int getCrawlingDepth()

Returns the current maximum allowed crawling depth.

Specified by:

getCrawlingDepth in interface ISCrawlerInterface

Returns:

The current allowed craling depth.

getCurrentDocument

public ISDocumentInterface getCurrentDocument()

Returns the last document visited by the Crawler.

Specified by:

getCurrentDocument in interface ISCrawlerInterface

Returns:

The last visited document as object that implements ISDocumentInterface (and contains all extracted links, words and their stems); null if no documents were crawled yet.

setCurrentDocument

public void setCurrentDocument(ISDocumentInterface isd)

Sets the last document visited by the Crawler.

Specified by:

setCurrentDocument in interface ISCrawlerInterface

Parameters:

The - last visited document as object that implements ISDocumentInterface (and contains all extracted links, words and their stems).

getCurrentURL

public java.net.URL getCurrentURL()

Returns the last URL visited by the Crawler.

Specified by:

getCurrentURL in interface ISCrawlerInterface

Returns:

The last visited URL; null if no links were crawled yet.

getMaxQueueSize

public int getMaxQueueSize()

Returns the maximum allowed size of the URL Queue

Specified by:

getMaxQueueSize in interface ISCrawlerInterface

Returns:

The max allowed Queue size

getQueueSize

public int getQueueSize()

Returns the current size of the URL queue

Specified by:

getQueueSize in interface ISCrawlerInterface

Returns:

The current size of the URL queue.

getState

public int getState()

Returns the current state of the crawler. Possible states are RUNNING and STOPPED.

Specified by:

getState in interface ISCrawlerInterface

Returns:

The current state of the crawler, RUNNING oder STOPPED

setState

public void setState(int state_code)

Sets the current state of the crawler. Possible states are RUNNING and STOPPED.

Specified by:

setState in interface ISCrawlerInterface

Parameters:

The - current state of the crawler, RUNNING oder STOPPED

getTimeout

public int getTimeout()

Returns the current timeout of the crawler.

Specified by:

getTimeout in interface ISCrawlerInterface

Returns:

The current timeout of the crawler.

setTimeout

public void setTimeout(int t)

Sets the current timeout of the crawler.

Specified by:

setTimeout in interface ISCrawlerInterface

Parameters:

t - The current timeout of the crawler in ms.

isVisited

public boolean isVisited(java.net.URL doc)

Checks if the URL of the given document is already visited by the crawler.

Specified by:

isVisited in interface ISCrawlerInterface

Returns:

true if the engine was able to recognize the given URL as already visited, false.

setCrawlingDepth

public void setCrawlingDepth(int depth)

Sets the maximum allowed crawling depth.

Specified by:

setCrawlingDepth in interface ISCrawlerInterface

Parameters:

depth - The maximum allowed craling depth.

setQueueMaxSize

public void setQueueMaxSize(int m)

Set the maximum allowed size of the URL queue

Specified by:

setQueueMaxSize in interface ISCrawlerInterface

Parameters:

m - The maximum allowed Queue size

start

public void start()

Starts the thread of the crawler and changes the engine state to RUNNING

Specified by:

start in interface ISCrawlerInterface

stop

public void stop()

Stops the crawler. This method stops crawling and sets the engine status to STOPPED.

Specified by:

stop in interface ISCrawlerInterface

reset

public void reset()

Resets the crawler. This method stops the crawling, resets the URL queue, and the list of visited links. Finally, it sets the crawler status to STOPPED,

Specified by:

reset in interface ISCrawlerInterface

run

public void run()

Specified by:

run in interface java.lang.Runnable

getNextURL

public java.net.URL getNextURL()

Returns the next URL to be searched. It is doing the job for getBest().

Specified by:

getNextURL in interface ISCrawlerInterface

Returns:

next URL in the queue.

isDataStructureEmpty

public boolean isDataStructureEmpty()

Checks if our data structure is empty or not.

Specified by:

isDataStructureEmpty in interface ISCrawlerInterface

Returns:

boolean value which is true if our data structure is empty

runParser

public ISDocumentInterface runParser(java.io.Reader r)

Starts the parser.

Specified by:

runParser in interface ISCrawlerInterface

Parameters:

Reader - which contains the URL to be parsed.

Returns:

ISDocumentInterface.

robotSafe

public boolean robotSafe(java.net.URL url)

Checks if there exists a robots.txt on the server and checks it contains a "Disallow:".

Specified by:

robotSafe in interface ISCrawlerInterface

Parameters:

url - URL which should be checked.

Returns:

true if the document can be parsed.

getContentType

public java.lang.String getContentType(java.net.URLConnection urlConnection)

Returns the ContentType of the current document.

Specified by:

getContentType in interface ISCrawlerInterface

Parameters:

urlConnection - The current document given by a URLConnection.

Returns:

The ContentType of the current document as String.

main

public static void main(java.lang.String[] args)