ir.webutils
Class LinkExtractor

java.lang.Object
  extended by javax.swing.text.html.HTMLEditorKit.ParserCallback
      extended by ir.webutils.LinkExtractor

public class LinkExtractor
extends javax.swing.text.html.HTMLEditorKit.ParserCallback

LinkExtractor defines a callback that extracts the links from an HTML document and provides functionality to parse a document. The extracted links are absolute. Uses the HTML parser in Java Swing to parse the document and find links and translate them to absolute URL's (instead of relative ones).


Field Summary
protected  java.util.List<Link> links
          The current list of extracted links
protected  HTMLPage page
          The page from which to extract links
protected  java.net.URL url
          The URL for this page
 
Fields inherited from class javax.swing.text.html.HTMLEditorKit.ParserCallback
IMPLIED
 
Constructor Summary
LinkExtractor(HTMLPage page)
          Create an link extractor for the given page
 
Method Summary
protected  void addLink(javax.swing.text.MutableAttributeSet attributes, javax.swing.text.html.HTML.Attribute attr)
          Retrieves a link from an attribute set and completes it against the base URL.
 java.util.List<Link> extractLinks()
          Extracts links from the given page.
 void handleEndTag(javax.swing.text.html.HTML.Tag tag, int position)
          Executed when a closing HTML tag is found in the document.
 void handleSimpleTag(javax.swing.text.html.HTML.Tag tag, javax.swing.text.MutableAttributeSet attributes, int position)
          Executed when an HTML tag that has no closing tag is found in the document.
 void handleStartTag(javax.swing.text.html.HTML.Tag tag, javax.swing.text.MutableAttributeSet attributes, int position)
          Executed when an opening HTML tag is found in the document.
 void handleText(char[] text, int position)
          Executed when a block of text is encountered.
 
Methods inherited from class javax.swing.text.html.HTMLEditorKit.ParserCallback
flush, handleComment, handleEndOfLineString, handleError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

links

protected java.util.List<Link> links
The current list of extracted links


page

protected HTMLPage page
The page from which to extract links


url

protected java.net.URL url
The URL for this page

Constructor Detail

LinkExtractor

public LinkExtractor(HTMLPage page)
Create an link extractor for the given page

Method Detail

handleText

public void handleText(char[] text,
                       int position)
Executed when a block of text is encountered. Just ignores text.

Overrides:
handleText in class javax.swing.text.html.HTMLEditorKit.ParserCallback
Parameters:
text - A char array representation of the text.
position - The position of the text in the document.

handleStartTag

public void handleStartTag(javax.swing.text.html.HTML.Tag tag,
                           javax.swing.text.MutableAttributeSet attributes,
                           int position)
Executed when an opening HTML tag is found in the document. Note that this method only handles tags that also have a closing tag. Catches "a" tags and adds links for them (after completing them)

Overrides:
handleStartTag in class javax.swing.text.html.HTMLEditorKit.ParserCallback
Parameters:
tag - The tag that caused this function to be executed.
attributes - The attributes of tag.
position - The start of the tag in the document. If the tag is implied (filled in by the parser but not actually present in the document) then position will correspond to that of the next encountered tag.

handleEndTag

public void handleEndTag(javax.swing.text.html.HTML.Tag tag,
                         int position)
Executed when a closing HTML tag is found in the document. Note that the parser may add "implied" closing tags. For example, the default parser adds closing <p> tags. This version just ignores end tags.

Overrides:
handleEndTag in class javax.swing.text.html.HTMLEditorKit.ParserCallback
Parameters:
tag - The tag found.
position - The position of the tag in the document.

handleSimpleTag

public void handleSimpleTag(javax.swing.text.html.HTML.Tag tag,
                            javax.swing.text.MutableAttributeSet attributes,
                            int position)
Executed when an HTML tag that has no closing tag is found in the document. Adds link for FRAME's

Overrides:
handleSimpleTag in class javax.swing.text.html.HTMLEditorKit.ParserCallback
Parameters:
tag - The tag that caused this function to be executed.
attributes - The attributes of tag.
position - The start of the tag in the document. If the tag is implied (filled in by the parser but not actually present in the document) then position will correspond to that of the next encountered tag.

extractLinks

public java.util.List<Link> extractLinks()
Extracts links from the given page. This method constructs a parser and registers this as the callback.

Returns:
A list of Link objects containing the links found on this page. The links will all be absolute links.

addLink

protected void addLink(javax.swing.text.MutableAttributeSet attributes,
                       javax.swing.text.html.HTML.Attribute attr)
Retrieves a link from an attribute set and completes it against the base URL.

Parameters:
attributes - The attribute set.
attr - The attribute that should be treated as a URL. For example, attr should be HTML.Attribute.HREF if attributes is from an anchor tag.