web crawler **** crawler4j

การพัฒนา WEB CRAWLER ขั้นพื้ นฐาน
ั นา
Eclipse IDE
Java SDK
Library “crawler4j”
download >>
“ https://code.google.com/p/crawler4j/ ”
การทางานของ web crawler
Initialize frontier
Dequeue URL
from frontier
Fetch page
Extract URLs and
add to frontier
Store page
Done ?
การทางานของ web crawler
ขั้นแรกจะเป็ นกระบวนการที่ใช้ในการเก็บ URL ของเว็บเพจ (Intialize
(Breadth First Search)
 ใช้คิวแบบเข้าก่อนออกก่อน (First In First Out : FIFO)
 หาข้อมูลโดยใช้เส้นทางในการค้นหาที่ส้น
ั ที่สุด (Shortest Paths)
 ใช้การค้นหาข้อมูลแนวกว้าง
ขั้นตอนในการดึง URL (Dequeue) ไปให้ส่วนที่ทาหน้าที่รอ้ งขอหรือ
ดาวน์โหลดเว็บเพจ (Fetch Page)
การทางานของ web crawler
ทาการสกัด URL (Extract URLs) จากเว็บเพจที่ถกู ดึงมาแล้วว่ามี
URL ที่ตอ้ งทางานต่ออีกหรือไม่
เป็ นการหาความลึกของลิงค์ (Link Depth) หากมีจะทาการบันทึก
URL นั้นลงในฐานข้อมูล
วนไปเริ่มกระบวนการใหม่จนกว่าจะไม่มลี ิงค์ URL จึงจะเสร็จสิ้ น
Step 1
Download the latest crawler4j-x.x.zip file (contains
zip file also contains a log4j.properties file that
you'll need later to properly create a log4j
download >>
“ https://code.google.com/p/crawler4j/ ”
Step 2
In Eclipse, create a new project, such
as WebcrawlerTest.
Right click on your new web crawler project and
select the Build Path option.
Select the “Add External Archives” option and select
ALL of the jar files that you extracted from the zip
Step 3
Create a Java class name “BasicCrawler”
import edu.uci.ics.crawler4j.crawler.Page;
import edu.uci.ics.crawler4j.crawler.WebCrawler;
import edu.uci.ics.crawler4j.parser.HtmlParseData;
import edu.uci.ics.crawler4j.url.WebURL;
import java.util.Set;
import java.util.regex.Pattern;
import org.apache.http.Header;
public class BasicCrawler extends WebCrawler {
private final static Pattern FILTERS = Pattern.compile(".*(\\.(css|js|bmp|gif|jpe?g" +
"|png|tiff?|mid|mp2|mp3|mp4"+ "|wav|avi|mov|mpeg|ram|m4v|pdf" +
Step 3
Create method name “shouldVisit”
Implement this function to specify whether the given
url . It should be crawled or not (based on crawling
public boolean shouldVisit(Page page, WebURL url) {
String href = url.getURL().toLowerCase();
return !FILTERS.matcher(href).matches() && href.startsWith("http://");
Step 3
Create method name “visit”
This function is called when a page is fetched and
ready to be processed by your program.
public void visit(Page page) {
int docid = page.getWebURL().getDocid();
String url = page.getWebURL().getURL();
String domain = page.getWebURL().getDomain();
String path = page.getWebURL().getPath();
String subDomain = page.getWebURL().getSubDomain();
String parentUrl = page.getWebURL().getParentUrl();
String anchor = page.getWebURL().getAnchor();
// continue next page >>>
Step 3
System.out.println("Docid: " + docid);
System.out.println("URL: " + url);
System.out.println("Domain: '" + domain + "'");
System.out.println("Sub-domain: '" + subDomain + "'");
System.out.println("Path: '" + path + "'");
System.out.println("Parent page: " + parentUrl);
System.out.println("Anchor text: " + anchor);
if (page.getParseData() instanceof HtmlParseData) {
HtmlParseData htmlParseData = (HtmlParseData) page.getParseData();
String text = htmlParseData.getText();
String html = htmlParseData.getHtml();
List<WebURL> links = htmlParseData.getOutgoingUrls();
System.out.println("Text length: " + text.length());
System.out.println("Html length: " + html.length());
System.out.println("Number of outgoing links: " + links.size());
Step 4
Create a Java class name “BasicCrawlController”
import edu.uci.ics.crawler4j.crawler.CrawlConfig;
import edu.uci.ics.crawler4j.crawler.CrawlController;
import edu.uci.ics.crawler4j.fetcher.PageFetcher;
import edu.uci.ics.crawler4j.robotstxt.RobotstxtConfig;
import edu.uci.ics.crawler4j.robotstxt.RobotstxtServer;
public class BasicCrawlController {
Step 4
Create main method
public static void main(String[] args) throws Exception {
String crawlStorageFolder = "C:\\Storage\\";
int numberOfCrawlers = 1
CrawlConfig config = new CrawlConfig();
//continue next page
Step 4
PageFetcher pageFetcher = new PageFetcher(config);
RobotstxtConfig robotstxtConfig = new RobotstxtConfig();
RobotstxtServer robotstxtServer = new
RobotstxtServer(robotstxtConfig, pageFetcher);
CrawlController controller = new CrawlController(config,
pageFetcher, robotstxtServer);
controller.start(BasicCrawler.class, numberOfCrawlers);
Step 5 Run
Select Run → Run Configurations option and select
your project and BasicCrawlController as the main
class. Click Apply button and then Run to start your
first webcrawler.
Deleting content of: C:\Storage\frontier
INFO [main] Crawler 1 started.
INFO [main] Crawler 2 started.
Step 5 Result
Docid: 1
URL: http://www.ics.uci.edu/~lopes/
Domain: 'uci.edu'
Sub-domain: 'www.ics'
Path: '/~lopes/'
Parent page: null
Anchor text: null
Text length: 2442
Html length: 9987
Number of outgoing links: 34
Step 5 Finish Crawl
INFO [Thread-1] It looks like no thread is working, waiting for 10 seconds to make sure...
INFO [Thread-1] No thread is working and no more URLs are in queue waiting for another 10 seconds to make sure...
INFO [Thread-1] All of the crawlers are stopped. Finishing the process...
INFO [Thread-1] Waiting for 10 seconds before final clean up...
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