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/*
* Jitsi, the OpenSource Java VoIP and Instant Messaging client.
*
* Distributable under LGPL license.
* See terms of license at gnu.org.
*/
package net.java.sip.communicator.util;
import java.io.*;
import javax.swing.text.html.*;
import javax.swing.text.html.parser.*;
/**
* A utility class that allows to extract the text content of an HTML page
* stripped from all formatting tags.
*
* @author Emil Ivov <emcho at sip-communicator.org>
* @author Yana Stamcheva
* @author Lubomir Marinov
*/
public class Html2Text
{
/**
* The <tt>Logger</tt> used by the <tt>Html2Text</tt> class for logging
* output.
*/
private static final Logger logger
= Logger.getLogger(Html2Text.class);
/**
* The HTML parser used by {@link #extractText(String)} to parse HTML so
* that plain text can be extracted from it.
*/
private static HTMLParserCallback parser;
/**
* A utility method that allows to extract the text content of an HTML page
* stripped from all formatting tags. Method is synchronized to avoid
* concurrent access to the underlying <tt>HTMLEditorKit</tt>.
*
* @param html the HTML string that we will extract the text from.
* @return the text content of the <tt>html</tt> parameter.
*/
public static synchronized String extractText(String html)
{
if(html == null)
return null;
if (parser == null)
parser = new HTMLParserCallback();
try
{
StringReader in = new StringReader(html);
try
{
return parser.parse(in);
}
finally
{
in.close();
}
}
catch (Exception ex)
{
if (logger.isInfoEnabled())
logger.info("Failed to extract plain text from html="+html, ex);
return html;
}
}
/**
* The ParserCallback that will parse the HTML.
*/
private static class HTMLParserCallback
extends HTMLEditorKit.ParserCallback
{
/**
* The <tt>StringBuilder</tt> which accumulates the parsed text while it
* is being parsed.
*/
private StringBuilder sb;
/**
* Parses the text contained in the given reader.
*
* @param in the reader to parse.
* @return the parsed text
* @throws IOException thrown if we fail to parse the reader.
*/
public String parse(Reader in)
throws IOException
{
sb = new StringBuilder();
String s;
try
{
new ParserDelegator().parse(in, this, /* ignoreCharSet */ true);
s = sb.toString();
}
finally
{
/*
* Since the Html2Text class keeps this instance in a static
* reference, the field sb should be reset to null as soon as
* completing its goad in order to avoid keeping the parsed
* text in memory after it is no longer needed i.e. to prevent
* a memory leak. This method has been converted to return the
* parsed string instead of having a separate getter method for
* the parsed string for the same purpose.
*/
sb = null;
}
return s;
}
/**
* Appends the given text to the string buffer.
*
* @param text the text of a text node which has been parsed from the
* specified HTML
* @param pos the zero-based position of the specified <tt>text</tt> in
* the specified HTML
*/
@Override
public void handleText(char[] text, int pos)
{
sb.append(text);
}
}
}
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